diff -r 000000000000 -r 6474c204b198 gfx/thebes/gfxFont.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gfx/thebes/gfxFont.cpp	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,7446 @@
+/* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/DebugOnly.h"
+#include "mozilla/MathAlgorithms.h"
+
+#ifdef MOZ_LOGGING
+#define FORCE_PR_LOG /* Allow logging in the release build */
+#endif
+#include "prlog.h"
+
+#include "nsServiceManagerUtils.h"
+#include "nsExpirationTracker.h"
+#include "nsILanguageAtomService.h"
+#include "nsITimer.h"
+
+#include "gfxFont.h"
+#include "gfxPlatform.h"
+#include "nsGkAtoms.h"
+
+#include "gfxTypes.h"
+#include "gfxContext.h"
+#include "gfxFontMissingGlyphs.h"
+#include "gfxHarfBuzzShaper.h"
+#include "gfxUserFontSet.h"
+#include "gfxPlatformFontList.h"
+#include "gfxScriptItemizer.h"
+#include "nsUnicodeProperties.h"
+#include "nsMathUtils.h"
+#include "nsBidiUtils.h"
+#include "nsUnicodeRange.h"
+#include "nsStyleConsts.h"
+#include "mozilla/FloatingPoint.h"
+#include "mozilla/Likely.h"
+#include "mozilla/MemoryReporting.h"
+#include "mozilla/Preferences.h"
+#include "mozilla/Services.h"
+#include "mozilla/Telemetry.h"
+#include "gfxSVGGlyphs.h"
+#include "gfxMathTable.h"
+#include "gfx2DGlue.h"
+
+#if defined(XP_MACOSX)
+#include "nsCocoaFeatures.h"
+#endif
+
+#include "cairo.h"
+#include "gfxFontTest.h"
+
+#include "harfbuzz/hb.h"
+#include "harfbuzz/hb-ot.h"
+#include "graphite2/Font.h"
+
+#include "nsCRT.h"
+#include "GeckoProfiler.h"
+#include "gfxFontConstants.h"
+
+#include <algorithm>
+
+using namespace mozilla;
+using namespace mozilla::gfx;
+using namespace mozilla::unicode;
+using mozilla::services::GetObserverService;
+
+gfxFontCache *gfxFontCache::gGlobalCache = nullptr;
+
+static const char16_t kEllipsisChar[] = { 0x2026, 0x0 };
+static const char16_t kASCIIPeriodsChar[] = { '.', '.', '.', 0x0 };
+
+#ifdef DEBUG_roc
+#define DEBUG_TEXT_RUN_STORAGE_METRICS
+#endif
+
+#ifdef DEBUG_TEXT_RUN_STORAGE_METRICS
+static uint32_t gTextRunStorageHighWaterMark = 0;
+static uint32_t gTextRunStorage = 0;
+static uint32_t gFontCount = 0;
+static uint32_t gGlyphExtentsCount = 0;
+static uint32_t gGlyphExtentsWidthsTotalSize = 0;
+static uint32_t gGlyphExtentsSetupEagerSimple = 0;
+static uint32_t gGlyphExtentsSetupEagerTight = 0;
+static uint32_t gGlyphExtentsSetupLazyTight = 0;
+static uint32_t gGlyphExtentsSetupFallBackToTight = 0;
+#endif
+
+#ifdef PR_LOGGING
+#define LOG_FONTINIT(args) PR_LOG(gfxPlatform::GetLog(eGfxLog_fontinit), \
+                                  PR_LOG_DEBUG, args)
+#define LOG_FONTINIT_ENABLED() PR_LOG_TEST( \
+                                        gfxPlatform::GetLog(eGfxLog_fontinit), \
+                                        PR_LOG_DEBUG)
+#endif // PR_LOGGING
+
+void
+gfxCharacterMap::NotifyReleased()
+{
+    gfxPlatformFontList *fontlist = gfxPlatformFontList::PlatformFontList();
+    if (mShared) {
+        fontlist->RemoveCmap(this);
+    }
+    delete this;
+}
+
+gfxFontEntry::gfxFontEntry() :
+    mItalic(false), mFixedPitch(false),
+    mIsProxy(false), mIsValid(true),
+    mIsBadUnderlineFont(false),
+    mIsUserFont(false),
+    mIsLocalUserFont(false),
+    mStandardFace(false),
+    mSymbolFont(false),
+    mIgnoreGDEF(false),
+    mIgnoreGSUB(false),
+    mSVGInitialized(false),
+    mMathInitialized(false),
+    mHasSpaceFeaturesInitialized(false),
+    mHasSpaceFeatures(false),
+    mHasSpaceFeaturesKerning(false),
+    mHasSpaceFeaturesNonKerning(false),
+    mSkipDefaultFeatureSpaceCheck(false),
+    mCheckedForGraphiteTables(false),
+    mHasCmapTable(false),
+    mGrFaceInitialized(false),
+    mWeight(500), mStretch(NS_FONT_STRETCH_NORMAL),
+    mUVSOffset(0), mUVSData(nullptr),
+    mLanguageOverride(NO_FONT_LANGUAGE_OVERRIDE),
+    mUnitsPerEm(0),
+    mHBFace(nullptr),
+    mGrFace(nullptr),
+    mGrFaceRefCnt(0)
+{
+    memset(&mDefaultSubSpaceFeatures, 0, sizeof(mDefaultSubSpaceFeatures));
+    memset(&mNonDefaultSubSpaceFeatures, 0, sizeof(mNonDefaultSubSpaceFeatures));
+}
+
+gfxFontEntry::gfxFontEntry(const nsAString& aName, bool aIsStandardFace) :
+    mName(aName), mItalic(false), mFixedPitch(false),
+    mIsProxy(false), mIsValid(true),
+    mIsBadUnderlineFont(false), mIsUserFont(false),
+    mIsLocalUserFont(false), mStandardFace(aIsStandardFace),
+    mSymbolFont(false),
+    mIgnoreGDEF(false),
+    mIgnoreGSUB(false),
+    mSVGInitialized(false),
+    mMathInitialized(false),
+    mHasSpaceFeaturesInitialized(false),
+    mHasSpaceFeatures(false),
+    mHasSpaceFeaturesKerning(false),
+    mHasSpaceFeaturesNonKerning(false),
+    mSkipDefaultFeatureSpaceCheck(false),
+    mCheckedForGraphiteTables(false),
+    mHasCmapTable(false),
+    mGrFaceInitialized(false),
+    mWeight(500), mStretch(NS_FONT_STRETCH_NORMAL),
+    mUVSOffset(0), mUVSData(nullptr),
+    mLanguageOverride(NO_FONT_LANGUAGE_OVERRIDE),
+    mUnitsPerEm(0),
+    mHBFace(nullptr),
+    mGrFace(nullptr),
+    mGrFaceRefCnt(0)
+{
+    memset(&mDefaultSubSpaceFeatures, 0, sizeof(mDefaultSubSpaceFeatures));
+    memset(&mNonDefaultSubSpaceFeatures, 0, sizeof(mNonDefaultSubSpaceFeatures));
+}
+
+gfxFontEntry::~gfxFontEntry()
+{
+    // For downloaded fonts, we need to tell the user font cache that this
+    // entry is being deleted.
+    if (!mIsProxy && IsUserFont() && !IsLocalUserFont()) {
+        gfxUserFontSet::UserFontCache::ForgetFont(this);
+    }
+
+    // By the time the entry is destroyed, all font instances that were
+    // using it should already have been deleted, and so the HB and/or Gr
+    // face objects should have been released.
+    MOZ_ASSERT(!mHBFace);
+    MOZ_ASSERT(!mGrFaceInitialized);
+}
+
+bool gfxFontEntry::IsSymbolFont() 
+{
+    return mSymbolFont;
+}
+
+bool gfxFontEntry::TestCharacterMap(uint32_t aCh)
+{
+    if (!mCharacterMap) {
+        ReadCMAP();
+        NS_ASSERTION(mCharacterMap, "failed to initialize character map");
+    }
+    return mCharacterMap->test(aCh);
+}
+
+nsresult gfxFontEntry::InitializeUVSMap()
+{
+    // mUVSOffset will not be initialized
+    // until cmap is initialized.
+    if (!mCharacterMap) {
+        ReadCMAP();
+        NS_ASSERTION(mCharacterMap, "failed to initialize character map");
+    }
+
+    if (!mUVSOffset) {
+        return NS_ERROR_FAILURE;
+    }
+
+    if (!mUVSData) {
+        const uint32_t kCmapTag = TRUETYPE_TAG('c','m','a','p');
+        AutoTable cmapTable(this, kCmapTag);
+        if (!cmapTable) {
+            mUVSOffset = 0; // don't bother to read the table again
+            return NS_ERROR_FAILURE;
+        }
+
+        uint8_t* uvsData;
+        unsigned int cmapLen;
+        const char* cmapData = hb_blob_get_data(cmapTable, &cmapLen);
+        nsresult rv = gfxFontUtils::ReadCMAPTableFormat14(
+                          (const uint8_t*)cmapData + mUVSOffset,
+                          cmapLen - mUVSOffset, uvsData);
+
+        if (NS_FAILED(rv)) {
+            mUVSOffset = 0; // don't bother to read the table again
+            return rv;
+        }
+
+        mUVSData = uvsData;
+    }
+
+    return NS_OK;
+}
+
+uint16_t gfxFontEntry::GetUVSGlyph(uint32_t aCh, uint32_t aVS)
+{
+    InitializeUVSMap();
+
+    if (mUVSData) {
+        return gfxFontUtils::MapUVSToGlyphFormat14(mUVSData, aCh, aVS);
+    }
+
+    return 0;
+}
+
+bool gfxFontEntry::SupportsScriptInGSUB(const hb_tag_t* aScriptTags)
+{
+    hb_face_t *face = GetHBFace();
+    if (!face) {
+        return false;
+    }
+
+    unsigned int index;
+    hb_tag_t     chosenScript;
+    bool found =
+        hb_ot_layout_table_choose_script(face, TRUETYPE_TAG('G','S','U','B'),
+                                         aScriptTags, &index, &chosenScript);
+    hb_face_destroy(face);
+
+    return found && chosenScript != TRUETYPE_TAG('D','F','L','T');
+}
+
+nsresult gfxFontEntry::ReadCMAP(FontInfoData *aFontInfoData)
+{
+    NS_ASSERTION(false, "using default no-op implementation of ReadCMAP");
+    mCharacterMap = new gfxCharacterMap();
+    return NS_OK;
+}
+
+nsString
+gfxFontEntry::RealFaceName()
+{
+    AutoTable nameTable(this, TRUETYPE_TAG('n','a','m','e'));
+    if (nameTable) {
+        nsAutoString name;
+        nsresult rv = gfxFontUtils::GetFullNameFromTable(nameTable, name);
+        if (NS_SUCCEEDED(rv)) {
+            return name;
+        }
+    }
+    return Name();
+}
+
+already_AddRefed<gfxFont>
+gfxFontEntry::FindOrMakeFont(const gfxFontStyle *aStyle, bool aNeedsBold)
+{
+    // the font entry name is the psname, not the family name
+    nsRefPtr<gfxFont> font = gfxFontCache::GetCache()->Lookup(this, aStyle);
+
+    if (!font) {
+        gfxFont *newFont = CreateFontInstance(aStyle, aNeedsBold);
+        if (!newFont)
+            return nullptr;
+        if (!newFont->Valid()) {
+            delete newFont;
+            return nullptr;
+        }
+        font = newFont;
+        gfxFontCache::GetCache()->AddNew(font);
+    }
+    return font.forget();
+}
+
+uint16_t
+gfxFontEntry::UnitsPerEm()
+{
+    if (!mUnitsPerEm) {
+        AutoTable headTable(this, TRUETYPE_TAG('h','e','a','d'));
+        if (headTable) {
+            uint32_t len;
+            const HeadTable* head =
+                reinterpret_cast<const HeadTable*>(hb_blob_get_data(headTable,
+                                                                    &len));
+            if (len >= sizeof(HeadTable)) {
+                mUnitsPerEm = head->unitsPerEm;
+            }
+        }
+
+        // if we didn't find a usable 'head' table, or if the value was
+        // outside the valid range, record it as invalid
+        if (mUnitsPerEm < kMinUPEM || mUnitsPerEm > kMaxUPEM) {
+            mUnitsPerEm = kInvalidUPEM;
+        }
+    }
+    return mUnitsPerEm;
+}
+
+bool
+gfxFontEntry::HasSVGGlyph(uint32_t aGlyphId)
+{
+    NS_ASSERTION(mSVGInitialized, "SVG data has not yet been loaded. TryGetSVGData() first.");
+    return mSVGGlyphs->HasSVGGlyph(aGlyphId);
+}
+
+bool
+gfxFontEntry::GetSVGGlyphExtents(gfxContext *aContext, uint32_t aGlyphId,
+                                 gfxRect *aResult)
+{
+    NS_ABORT_IF_FALSE(mSVGInitialized,
+                      "SVG data has not yet been loaded. TryGetSVGData() first.");
+    NS_ABORT_IF_FALSE(mUnitsPerEm >= kMinUPEM && mUnitsPerEm <= kMaxUPEM,
+                      "font has invalid unitsPerEm");
+
+    gfxContextAutoSaveRestore matrixRestore(aContext);
+    cairo_matrix_t fontMatrix;
+    cairo_get_font_matrix(aContext->GetCairo(), &fontMatrix);
+
+    gfxMatrix svgToAppSpace = *reinterpret_cast<gfxMatrix*>(&fontMatrix);
+    svgToAppSpace.Scale(1.0f / mUnitsPerEm, 1.0f / mUnitsPerEm);
+
+    return mSVGGlyphs->GetGlyphExtents(aGlyphId, svgToAppSpace, aResult);
+}
+
+bool
+gfxFontEntry::RenderSVGGlyph(gfxContext *aContext, uint32_t aGlyphId,
+                             int aDrawMode, gfxTextContextPaint *aContextPaint)
+{
+    NS_ASSERTION(mSVGInitialized, "SVG data has not yet been loaded. TryGetSVGData() first.");
+    return mSVGGlyphs->RenderGlyph(aContext, aGlyphId, DrawMode(aDrawMode),
+                                   aContextPaint);
+}
+
+bool
+gfxFontEntry::TryGetSVGData(gfxFont* aFont)
+{
+    if (!gfxPlatform::GetPlatform()->OpenTypeSVGEnabled()) {
+        return false;
+    }
+
+    if (!mSVGInitialized) {
+        mSVGInitialized = true;
+
+        // If UnitsPerEm is not known/valid, we can't use SVG glyphs
+        if (UnitsPerEm() == kInvalidUPEM) {
+            return false;
+        }
+
+        // We don't use AutoTable here because we'll pass ownership of this
+        // blob to the gfxSVGGlyphs, once we've confirmed the table exists
+        hb_blob_t *svgTable = GetFontTable(TRUETYPE_TAG('S','V','G',' '));
+        if (!svgTable) {
+            return false;
+        }
+
+        // gfxSVGGlyphs will hb_blob_destroy() the table when it is finished
+        // with it.
+        mSVGGlyphs = new gfxSVGGlyphs(svgTable, this);
+    }
+
+    if (!mFontsUsingSVGGlyphs.Contains(aFont)) {
+        mFontsUsingSVGGlyphs.AppendElement(aFont);
+    }
+
+    return !!mSVGGlyphs;
+}
+
+void
+gfxFontEntry::NotifyFontDestroyed(gfxFont* aFont)
+{
+    mFontsUsingSVGGlyphs.RemoveElement(aFont);
+}
+
+void
+gfxFontEntry::NotifyGlyphsChanged()
+{
+    for (uint32_t i = 0, count = mFontsUsingSVGGlyphs.Length(); i < count; ++i) {
+        gfxFont* font = mFontsUsingSVGGlyphs[i];
+        font->NotifyGlyphsChanged();
+    }
+}
+
+bool
+gfxFontEntry::TryGetMathTable(gfxFont* aFont)
+{
+    if (!mMathInitialized) {
+        mMathInitialized = true;
+
+        // If UnitsPerEm is not known/valid, we can't use MATH table
+        if (UnitsPerEm() == kInvalidUPEM) {
+            return false;
+        }
+
+        // We don't use AutoTable here because we'll pass ownership of this
+        // blob to the gfxMathTable, once we've confirmed the table exists
+        hb_blob_t *mathTable = GetFontTable(TRUETYPE_TAG('M','A','T','H'));
+        if (!mathTable) {
+            return false;
+        }
+
+        // gfxMathTable will hb_blob_destroy() the table when it is finished
+        // with it.
+        mMathTable = new gfxMathTable(mathTable);
+        if (!mMathTable->HasValidHeaders()) {
+            mMathTable = nullptr;
+            return false;
+        }
+    }
+
+    return !!mMathTable;
+}
+
+gfxFloat
+gfxFontEntry::GetMathConstant(gfxFontEntry::MathConstant aConstant)
+{
+    NS_ASSERTION(mMathTable, "Math data has not yet been loaded. TryGetMathData() first.");
+    gfxFloat value = mMathTable->GetMathConstant(aConstant);
+    if (aConstant == gfxFontEntry::ScriptPercentScaleDown ||
+        aConstant == gfxFontEntry::ScriptScriptPercentScaleDown ||
+        aConstant == gfxFontEntry::RadicalDegreeBottomRaisePercent) {
+        return value / 100.0;
+    }
+    return value / mUnitsPerEm;
+}
+
+bool
+gfxFontEntry::GetMathItalicsCorrection(uint32_t aGlyphID,
+                                       gfxFloat* aItalicCorrection)
+{
+    NS_ASSERTION(mMathTable, "Math data has not yet been loaded. TryGetMathData() first.");
+    int16_t italicCorrection;
+    if (!mMathTable->GetMathItalicsCorrection(aGlyphID, &italicCorrection)) {
+        return false;
+    }
+    *aItalicCorrection = gfxFloat(italicCorrection) / mUnitsPerEm;
+    return true;
+}
+
+uint32_t
+gfxFontEntry::GetMathVariantsSize(uint32_t aGlyphID, bool aVertical,
+                                  uint16_t aSize)
+{
+    NS_ASSERTION(mMathTable, "Math data has not yet been loaded. TryGetMathData() first.");
+    return mMathTable->GetMathVariantsSize(aGlyphID, aVertical, aSize);
+}
+
+bool
+gfxFontEntry::GetMathVariantsParts(uint32_t aGlyphID, bool aVertical,
+                                   uint32_t aGlyphs[4])
+{
+    NS_ASSERTION(mMathTable, "Math data has not yet been loaded. TryGetMathData() first.");
+    return mMathTable->GetMathVariantsParts(aGlyphID, aVertical, aGlyphs);
+}
+
+/**
+ * FontTableBlobData
+ *
+ * See FontTableHashEntry for the general strategy.
+ */
+
+class gfxFontEntry::FontTableBlobData {
+public:
+    // Adopts the content of aBuffer.
+    FontTableBlobData(FallibleTArray<uint8_t>& aBuffer)
+        : mHashtable(nullptr), mHashKey(0)
+    {
+        MOZ_COUNT_CTOR(FontTableBlobData);
+        mTableData.SwapElements(aBuffer);
+    }
+
+    ~FontTableBlobData() {
+        MOZ_COUNT_DTOR(FontTableBlobData);
+        if (mHashtable && mHashKey) {
+            mHashtable->RemoveEntry(mHashKey);
+        }
+    }
+
+    // Useful for creating blobs
+    const char *GetTable() const
+    {
+        return reinterpret_cast<const char*>(mTableData.Elements());
+    }
+    uint32_t GetTableLength() const { return mTableData.Length(); }
+
+    // Tell this FontTableBlobData to remove the HashEntry when this is
+    // destroyed.
+    void ManageHashEntry(nsTHashtable<FontTableHashEntry> *aHashtable,
+                         uint32_t aHashKey)
+    {
+        mHashtable = aHashtable;
+        mHashKey = aHashKey;
+    }
+
+    // Disconnect from the HashEntry (because the blob has already been
+    // removed from the hashtable).
+    void ForgetHashEntry()
+    {
+        mHashtable = nullptr;
+        mHashKey = 0;
+    }
+
+    size_t SizeOfExcludingThis(MallocSizeOf aMallocSizeOf) const {
+        return mTableData.SizeOfExcludingThis(aMallocSizeOf);
+    }
+    size_t SizeOfIncludingThis(MallocSizeOf aMallocSizeOf) const {
+        return aMallocSizeOf(this) + SizeOfExcludingThis(aMallocSizeOf);
+    }
+
+private:
+    // The font table data block, owned (via adoption)
+    FallibleTArray<uint8_t> mTableData;
+
+    // The blob destroy function needs to know the owning hashtable
+    // and the hashtable key, so that it can remove the entry.
+    nsTHashtable<FontTableHashEntry> *mHashtable;
+    uint32_t                          mHashKey;
+
+    // not implemented
+    FontTableBlobData(const FontTableBlobData&);
+};
+
+hb_blob_t *
+gfxFontEntry::FontTableHashEntry::
+ShareTableAndGetBlob(FallibleTArray<uint8_t>& aTable,
+                     nsTHashtable<FontTableHashEntry> *aHashtable)
+{
+    Clear();
+    // adopts elements of aTable
+    mSharedBlobData = new FontTableBlobData(aTable);
+    mBlob = hb_blob_create(mSharedBlobData->GetTable(),
+                           mSharedBlobData->GetTableLength(),
+                           HB_MEMORY_MODE_READONLY,
+                           mSharedBlobData, DeleteFontTableBlobData);
+    if (!mSharedBlobData) {
+        // The FontTableBlobData was destroyed during hb_blob_create().
+        // The (empty) blob is still be held in the hashtable with a strong
+        // reference.
+        return hb_blob_reference(mBlob);
+    }
+
+    // Tell the FontTableBlobData to remove this hash entry when destroyed.
+    // The hashtable does not keep a strong reference.
+    mSharedBlobData->ManageHashEntry(aHashtable, GetKey());
+    return mBlob;
+}
+
+void
+gfxFontEntry::FontTableHashEntry::Clear()
+{
+    // If the FontTableBlobData is managing the hash entry, then the blob is
+    // not owned by this HashEntry; otherwise there is strong reference to the
+    // blob that must be removed.
+    if (mSharedBlobData) {
+        mSharedBlobData->ForgetHashEntry();
+        mSharedBlobData = nullptr;
+    } else if (mBlob) {
+        hb_blob_destroy(mBlob);
+    }
+    mBlob = nullptr;
+}
+
+// a hb_destroy_func for hb_blob_create
+
+/* static */ void
+gfxFontEntry::FontTableHashEntry::DeleteFontTableBlobData(void *aBlobData)
+{
+    delete static_cast<FontTableBlobData*>(aBlobData);
+}
+
+hb_blob_t *
+gfxFontEntry::FontTableHashEntry::GetBlob() const
+{
+    return hb_blob_reference(mBlob);
+}
+
+bool
+gfxFontEntry::GetExistingFontTable(uint32_t aTag, hb_blob_t **aBlob)
+{
+    if (!mFontTableCache) {
+        // we do this here rather than on fontEntry construction
+        // because not all shapers will access the table cache at all
+        mFontTableCache = new nsTHashtable<FontTableHashEntry>(10);
+    }
+
+    FontTableHashEntry *entry = mFontTableCache->GetEntry(aTag);
+    if (!entry) {
+        return false;
+    }
+
+    *aBlob = entry->GetBlob();
+    return true;
+}
+
+hb_blob_t *
+gfxFontEntry::ShareFontTableAndGetBlob(uint32_t aTag,
+                                       FallibleTArray<uint8_t>* aBuffer)
+{
+    if (MOZ_UNLIKELY(!mFontTableCache)) {
+        // we do this here rather than on fontEntry construction
+        // because not all shapers will access the table cache at all
+      mFontTableCache = new nsTHashtable<FontTableHashEntry>(10);
+    }
+
+    FontTableHashEntry *entry = mFontTableCache->PutEntry(aTag);
+    if (MOZ_UNLIKELY(!entry)) { // OOM
+        return nullptr;
+    }
+
+    if (!aBuffer) {
+        // ensure the entry is null
+        entry->Clear();
+        return nullptr;
+    }
+
+    return entry->ShareTableAndGetBlob(*aBuffer, mFontTableCache);
+}
+
+static int
+DirEntryCmp(const void* aKey, const void* aItem)
+{
+    int32_t tag = *static_cast<const int32_t*>(aKey);
+    const TableDirEntry* entry = static_cast<const TableDirEntry*>(aItem);
+    return tag - int32_t(entry->tag);
+}
+
+hb_blob_t*
+gfxFontEntry::GetTableFromFontData(const void* aFontData, uint32_t aTableTag)
+{
+    const SFNTHeader* header =
+        reinterpret_cast<const SFNTHeader*>(aFontData);
+    const TableDirEntry* dir =
+        reinterpret_cast<const TableDirEntry*>(header + 1);
+    dir = static_cast<const TableDirEntry*>
+        (bsearch(&aTableTag, dir, uint16_t(header->numTables),
+                 sizeof(TableDirEntry), DirEntryCmp));
+    if (dir) {
+        return hb_blob_create(reinterpret_cast<const char*>(aFontData) +
+                                  dir->offset, dir->length,
+                              HB_MEMORY_MODE_READONLY, nullptr, nullptr);
+
+    }
+    return nullptr;
+}
+
+already_AddRefed<gfxCharacterMap>
+gfxFontEntry::GetCMAPFromFontInfo(FontInfoData *aFontInfoData,
+                                  uint32_t& aUVSOffset,
+                                  bool& aSymbolFont)
+{
+    if (!aFontInfoData || !aFontInfoData->mLoadCmaps) {
+        return nullptr;
+    }
+
+    return aFontInfoData->GetCMAP(mName, aUVSOffset, aSymbolFont);
+}
+
+hb_blob_t *
+gfxFontEntry::GetFontTable(uint32_t aTag)
+{
+    hb_blob_t *blob;
+    if (GetExistingFontTable(aTag, &blob)) {
+        return blob;
+    }
+
+    FallibleTArray<uint8_t> buffer;
+    bool haveTable = NS_SUCCEEDED(CopyFontTable(aTag, buffer));
+
+    return ShareFontTableAndGetBlob(aTag, haveTable ? &buffer : nullptr);
+}
+
+// callback for HarfBuzz to get a font table (in hb_blob_t form)
+// from the font entry (passed as aUserData)
+/*static*/ hb_blob_t *
+gfxFontEntry::HBGetTable(hb_face_t *face, uint32_t aTag, void *aUserData)
+{
+    gfxFontEntry *fontEntry = static_cast<gfxFontEntry*>(aUserData);
+
+    // bug 589682 - ignore the GDEF table in buggy fonts (applies to
+    // Italic and BoldItalic faces of Times New Roman)
+    if (aTag == TRUETYPE_TAG('G','D','E','F') &&
+        fontEntry->IgnoreGDEF()) {
+        return nullptr;
+    }
+
+    // bug 721719 - ignore the GSUB table in buggy fonts (applies to Roboto,
+    // at least on some Android ICS devices; set in gfxFT2FontList.cpp)
+    if (aTag == TRUETYPE_TAG('G','S','U','B') &&
+        fontEntry->IgnoreGSUB()) {
+        return nullptr;
+    }
+
+    return fontEntry->GetFontTable(aTag);
+}
+
+/*static*/ void
+gfxFontEntry::HBFaceDeletedCallback(void *aUserData)
+{
+    gfxFontEntry *fe = static_cast<gfxFontEntry*>(aUserData);
+    fe->ForgetHBFace();
+}
+
+void
+gfxFontEntry::ForgetHBFace()
+{
+    mHBFace = nullptr;
+}
+
+hb_face_t*
+gfxFontEntry::GetHBFace()
+{
+    if (!mHBFace) {
+        mHBFace = hb_face_create_for_tables(HBGetTable, this,
+                                            HBFaceDeletedCallback);
+        return mHBFace;
+    }
+    return hb_face_reference(mHBFace);
+}
+
+/*static*/ const void*
+gfxFontEntry::GrGetTable(const void *aAppFaceHandle, unsigned int aName,
+                         size_t *aLen)
+{
+    gfxFontEntry *fontEntry =
+        static_cast<gfxFontEntry*>(const_cast<void*>(aAppFaceHandle));
+    hb_blob_t *blob = fontEntry->GetFontTable(aName);
+    if (blob) {
+        unsigned int blobLength;
+        const void *tableData = hb_blob_get_data(blob, &blobLength);
+        fontEntry->mGrTableMap->Put(tableData, blob);
+        *aLen = blobLength;
+        return tableData;
+    }
+    *aLen = 0;
+    return nullptr;
+}
+
+/*static*/ void
+gfxFontEntry::GrReleaseTable(const void *aAppFaceHandle,
+                             const void *aTableBuffer)
+{
+    gfxFontEntry *fontEntry =
+        static_cast<gfxFontEntry*>(const_cast<void*>(aAppFaceHandle));
+    void *data;
+    if (fontEntry->mGrTableMap->Get(aTableBuffer, &data)) {
+        fontEntry->mGrTableMap->Remove(aTableBuffer);
+        hb_blob_destroy(static_cast<hb_blob_t*>(data));
+    }
+}
+
+gr_face*
+gfxFontEntry::GetGrFace()
+{
+    if (!mGrFaceInitialized) {
+        gr_face_ops faceOps = {
+            sizeof(gr_face_ops),
+            GrGetTable,
+            GrReleaseTable
+        };
+        mGrTableMap = new nsDataHashtable<nsPtrHashKey<const void>,void*>;
+        mGrFace = gr_make_face_with_ops(this, &faceOps, gr_face_default);
+        mGrFaceInitialized = true;
+    }
+    ++mGrFaceRefCnt;
+    return mGrFace;
+}
+
+void
+gfxFontEntry::ReleaseGrFace(gr_face *aFace)
+{
+    MOZ_ASSERT(aFace == mGrFace); // sanity-check
+    MOZ_ASSERT(mGrFaceRefCnt > 0);
+    if (--mGrFaceRefCnt == 0) {
+        gr_face_destroy(mGrFace);
+        mGrFace = nullptr;
+        mGrFaceInitialized = false;
+        delete mGrTableMap;
+        mGrTableMap = nullptr;
+    }
+}
+
+void
+gfxFontEntry::DisconnectSVG()
+{
+    if (mSVGInitialized && mSVGGlyphs) {
+        mSVGGlyphs = nullptr;
+        mSVGInitialized = false;
+    }
+}
+
+bool
+gfxFontEntry::HasFontTable(uint32_t aTableTag)
+{
+    AutoTable table(this, aTableTag);
+    return table && hb_blob_get_length(table) > 0;
+}
+
+void
+gfxFontEntry::CheckForGraphiteTables()
+{
+    mHasGraphiteTables = HasFontTable(TRUETYPE_TAG('S','i','l','f'));
+}
+
+/* static */ size_t
+gfxFontEntry::FontTableHashEntry::SizeOfEntryExcludingThis
+    (FontTableHashEntry *aEntry,
+     MallocSizeOf aMallocSizeOf,
+     void* aUserArg)
+{
+    size_t n = 0;
+    if (aEntry->mBlob) {
+        n += aMallocSizeOf(aEntry->mBlob);
+    }
+    if (aEntry->mSharedBlobData) {
+        n += aEntry->mSharedBlobData->SizeOfIncludingThis(aMallocSizeOf);
+    }
+    return n;
+}
+
+void
+gfxFontEntry::AddSizeOfExcludingThis(MallocSizeOf aMallocSizeOf,
+                                     FontListSizes* aSizes) const
+{
+    aSizes->mFontListSize += mName.SizeOfExcludingThisIfUnshared(aMallocSizeOf);
+
+    // cmaps are shared so only non-shared cmaps are included here
+    if (mCharacterMap && mCharacterMap->mBuildOnTheFly) {
+        aSizes->mCharMapsSize +=
+            mCharacterMap->SizeOfIncludingThis(aMallocSizeOf);
+    }
+    if (mFontTableCache) {
+        aSizes->mFontTableCacheSize +=
+            mFontTableCache->SizeOfExcludingThis(
+                FontTableHashEntry::SizeOfEntryExcludingThis,
+                aMallocSizeOf);
+    }
+}
+
+void
+gfxFontEntry::AddSizeOfIncludingThis(MallocSizeOf aMallocSizeOf,
+                                     FontListSizes* aSizes) const
+{
+    aSizes->mFontListSize += aMallocSizeOf(this);
+    AddSizeOfExcludingThis(aMallocSizeOf, aSizes);
+}
+
+//////////////////////////////////////////////////////////////////////////////
+//
+// class gfxFontFamily
+//
+//////////////////////////////////////////////////////////////////////////////
+
+// we consider faces with mStandardFace == true to be "greater than" those with false,
+// because during style matching, later entries will replace earlier ones
+class FontEntryStandardFaceComparator {
+  public:
+    bool Equals(const nsRefPtr<gfxFontEntry>& a, const nsRefPtr<gfxFontEntry>& b) const {
+        return a->mStandardFace == b->mStandardFace;
+    }
+    bool LessThan(const nsRefPtr<gfxFontEntry>& a, const nsRefPtr<gfxFontEntry>& b) const {
+        return (a->mStandardFace == false && b->mStandardFace == true);
+    }
+};
+
+void
+gfxFontFamily::SortAvailableFonts()
+{
+    mAvailableFonts.Sort(FontEntryStandardFaceComparator());
+}
+
+bool
+gfxFontFamily::HasOtherFamilyNames()
+{
+    // need to read in other family names to determine this
+    if (!mOtherFamilyNamesInitialized) {
+        ReadOtherFamilyNames(gfxPlatformFontList::PlatformFontList());  // sets mHasOtherFamilyNames
+    }
+    return mHasOtherFamilyNames;
+}
+
+gfxFontEntry*
+gfxFontFamily::FindFontForStyle(const gfxFontStyle& aFontStyle, 
+                                bool& aNeedsSyntheticBold)
+{
+    if (!mHasStyles)
+        FindStyleVariations(); // collect faces for the family, if not already done
+
+    NS_ASSERTION(mAvailableFonts.Length() > 0, "font family with no faces!");
+
+    aNeedsSyntheticBold = false;
+
+    int8_t baseWeight = aFontStyle.ComputeWeight();
+    bool wantBold = baseWeight >= 6;
+
+    // If the family has only one face, we simply return it; no further checking needed
+    if (mAvailableFonts.Length() == 1) {
+        gfxFontEntry *fe = mAvailableFonts[0];
+        aNeedsSyntheticBold = wantBold && !fe->IsBold();
+        return fe;
+    }
+
+    bool wantItalic = (aFontStyle.style &
+                       (NS_FONT_STYLE_ITALIC | NS_FONT_STYLE_OBLIQUE)) != 0;
+
+    // Most families are "simple", having just Regular/Bold/Italic/BoldItalic,
+    // or some subset of these. In this case, we have exactly 4 entries in mAvailableFonts,
+    // stored in the above order; note that some of the entries may be nullptr.
+    // We can then pick the required entry based on whether the request is for
+    // bold or non-bold, italic or non-italic, without running the more complex
+    // matching algorithm used for larger families with many weights and/or widths.
+
+    if (mIsSimpleFamily) {
+        // Family has no more than the "standard" 4 faces, at fixed indexes;
+        // calculate which one we want.
+        // Note that we cannot simply return it as not all 4 faces are necessarily present.
+        uint8_t faceIndex = (wantItalic ? kItalicMask : 0) |
+                            (wantBold ? kBoldMask : 0);
+
+        // if the desired style is available, return it directly
+        gfxFontEntry *fe = mAvailableFonts[faceIndex];
+        if (fe) {
+            // no need to set aNeedsSyntheticBold here as we matched the boldness request
+            return fe;
+        }
+
+        // order to check fallback faces in a simple family, depending on requested style
+        static const uint8_t simpleFallbacks[4][3] = {
+            { kBoldFaceIndex, kItalicFaceIndex, kBoldItalicFaceIndex },   // fallbacks for Regular
+            { kRegularFaceIndex, kBoldItalicFaceIndex, kItalicFaceIndex },// Bold
+            { kBoldItalicFaceIndex, kRegularFaceIndex, kBoldFaceIndex },  // Italic
+            { kItalicFaceIndex, kBoldFaceIndex, kRegularFaceIndex }       // BoldItalic
+        };
+        const uint8_t *order = simpleFallbacks[faceIndex];
+
+        for (uint8_t trial = 0; trial < 3; ++trial) {
+            // check remaining faces in order of preference to find the first that actually exists
+            fe = mAvailableFonts[order[trial]];
+            if (fe) {
+                aNeedsSyntheticBold = wantBold && !fe->IsBold();
+                return fe;
+            }
+        }
+
+        // this can't happen unless we have totally broken the font-list manager!
+        NS_NOTREACHED("no face found in simple font family!");
+        return nullptr;
+    }
+
+    // This is a large/rich font family, so we do full style- and weight-matching:
+    // first collect a list of weights that are the best match for the requested
+    // font-stretch and font-style, then pick the best weight match among those
+    // available.
+
+    gfxFontEntry *weightList[10] = { 0 };
+    bool foundWeights = FindWeightsForStyle(weightList, wantItalic, aFontStyle.stretch);
+    if (!foundWeights) {
+        return nullptr;
+    }
+
+    // First find a match for the best weight
+    int8_t matchBaseWeight = 0;
+    int8_t i = baseWeight;
+
+    // Need to special case when normal face doesn't exist but medium does.
+    // In that case, use medium otherwise weights < 400
+    if (baseWeight == 4 && !weightList[4]) {
+        i = 5; // medium
+    }
+
+    // Loop through weights, since one exists loop will terminate
+    int8_t direction = (baseWeight > 5) ? 1 : -1;
+    for (; ; i += direction) {
+        if (weightList[i]) {
+            matchBaseWeight = i;
+            break;
+        }
+
+        // If we've reached one side without finding a font,
+        // start over and go the other direction until we find a match
+        if (i == 1 || i == 9) {
+            i = baseWeight;
+            direction = -direction;
+        }
+    }
+
+    NS_ASSERTION(matchBaseWeight != 0, 
+                 "weight mapping should always find at least one font in a family");
+
+    gfxFontEntry *matchFE = weightList[matchBaseWeight];
+
+    NS_ASSERTION(matchFE,
+                 "weight mapping should always find at least one font in a family");
+
+    if (!matchFE->IsBold() && baseWeight >= 6)
+    {
+        aNeedsSyntheticBold = true;
+    }
+
+    return matchFE;
+}
+
+void
+gfxFontFamily::CheckForSimpleFamily()
+{
+    // already checked this family
+    if (mIsSimpleFamily) {
+        return;
+    };
+
+    uint32_t count = mAvailableFonts.Length();
+    if (count > 4 || count == 0) {
+        return; // can't be "simple" if there are >4 faces;
+                // if none then the family is unusable anyway
+    }
+
+    if (count == 1) {
+        mIsSimpleFamily = true;
+        return;
+    }
+
+    int16_t firstStretch = mAvailableFonts[0]->Stretch();
+
+    gfxFontEntry *faces[4] = { 0 };
+    for (uint8_t i = 0; i < count; ++i) {
+        gfxFontEntry *fe = mAvailableFonts[i];
+        if (fe->Stretch() != firstStretch) {
+            return; // font-stretch doesn't match, don't treat as simple family
+        }
+        uint8_t faceIndex = (fe->IsItalic() ? kItalicMask : 0) |
+                            (fe->Weight() >= 600 ? kBoldMask : 0);
+        if (faces[faceIndex]) {
+            return; // two faces resolve to the same slot; family isn't "simple"
+        }
+        faces[faceIndex] = fe;
+    }
+
+    // we have successfully slotted the available faces into the standard
+    // 4-face framework
+    mAvailableFonts.SetLength(4);
+    for (uint8_t i = 0; i < 4; ++i) {
+        if (mAvailableFonts[i].get() != faces[i]) {
+            mAvailableFonts[i].swap(faces[i]);
+        }
+    }
+
+    mIsSimpleFamily = true;
+}
+
+static inline uint32_t
+StyleDistance(gfxFontEntry *aFontEntry,
+              bool anItalic, int16_t aStretch)
+{
+    // Compute a measure of the "distance" between the requested style
+    // and the given fontEntry,
+    // considering italicness and font-stretch but not weight.
+
+    int32_t distance = 0;
+    if (aStretch != aFontEntry->mStretch) {
+        // stretch values are in the range -4 .. +4
+        // if aStretch is positive, we prefer more-positive values;
+        // if zero or negative, prefer more-negative
+        if (aStretch > 0) {
+            distance = (aFontEntry->mStretch - aStretch) * 2;
+        } else {
+            distance = (aStretch - aFontEntry->mStretch) * 2;
+        }
+        // if the computed "distance" here is negative, it means that
+        // aFontEntry lies in the "non-preferred" direction from aStretch,
+        // so we treat that as larger than any preferred-direction distance
+        // (max possible is 8) by adding an extra 10 to the absolute value
+        if (distance < 0) {
+            distance = -distance + 10;
+        }
+    }
+    if (aFontEntry->IsItalic() != anItalic) {
+        distance += 1;
+    }
+    return uint32_t(distance);
+}
+
+bool
+gfxFontFamily::FindWeightsForStyle(gfxFontEntry* aFontsForWeights[],
+                                   bool anItalic, int16_t aStretch)
+{
+    uint32_t foundWeights = 0;
+    uint32_t bestMatchDistance = 0xffffffff;
+
+    uint32_t count = mAvailableFonts.Length();
+    for (uint32_t i = 0; i < count; i++) {
+        // this is not called for "simple" families, and therefore it does not
+        // need to check the mAvailableFonts entries for nullptr.
+        gfxFontEntry *fe = mAvailableFonts[i];
+        uint32_t distance = StyleDistance(fe, anItalic, aStretch);
+        if (distance <= bestMatchDistance) {
+            int8_t wt = fe->mWeight / 100;
+            NS_ASSERTION(wt >= 1 && wt < 10, "invalid weight in fontEntry");
+            if (!aFontsForWeights[wt]) {
+                // record this as a possible candidate for weight matching
+                aFontsForWeights[wt] = fe;
+                ++foundWeights;
+            } else {
+                uint32_t prevDistance =
+                    StyleDistance(aFontsForWeights[wt], anItalic, aStretch);
+                if (prevDistance >= distance) {
+                    // replacing a weight we already found,
+                    // so don't increment foundWeights
+                    aFontsForWeights[wt] = fe;
+                }
+            }
+            bestMatchDistance = distance;
+        }
+    }
+
+    NS_ASSERTION(foundWeights > 0, "Font family containing no faces?");
+
+    if (foundWeights == 1) {
+        // no need to cull entries if we only found one weight
+        return true;
+    }
+
+    // we might have recorded some faces that were a partial style match, but later found
+    // others that were closer; in this case, we need to cull the poorer matches from the
+    // weight list we'll return
+    for (uint32_t i = 0; i < 10; ++i) {
+        if (aFontsForWeights[i] &&
+            StyleDistance(aFontsForWeights[i], anItalic, aStretch) > bestMatchDistance)
+        {
+            aFontsForWeights[i] = 0;
+        }
+    }
+
+    return (foundWeights > 0);
+}
+
+
+void gfxFontFamily::LocalizedName(nsAString& aLocalizedName)
+{
+    // just return the primary name; subclasses should override
+    aLocalizedName = mName;
+}
+
+// metric for how close a given font matches a style
+static int32_t
+CalcStyleMatch(gfxFontEntry *aFontEntry, const gfxFontStyle *aStyle)
+{
+    int32_t rank = 0;
+    if (aStyle) {
+         // italics
+         bool wantItalic =
+             (aStyle->style & (NS_FONT_STYLE_ITALIC | NS_FONT_STYLE_OBLIQUE)) != 0;
+         if (aFontEntry->IsItalic() == wantItalic) {
+             rank += 10;
+         }
+
+        // measure of closeness of weight to the desired value
+        rank += 9 - DeprecatedAbs(aFontEntry->Weight() / 100 - aStyle->ComputeWeight());
+    } else {
+        // if no font to match, prefer non-bold, non-italic fonts
+        if (!aFontEntry->IsItalic()) {
+            rank += 3;
+        }
+        if (!aFontEntry->IsBold()) {
+            rank += 2;
+        }
+    }
+
+    return rank;
+}
+
+#define RANK_MATCHED_CMAP   20
+
+void
+gfxFontFamily::FindFontForChar(GlobalFontMatch *aMatchData)
+{
+    if (mFamilyCharacterMapInitialized && !TestCharacterMap(aMatchData->mCh)) {
+        // none of the faces in the family support the required char,
+        // so bail out immediately
+        return;
+    }
+
+    bool needsBold;
+    gfxFontStyle normal;
+    gfxFontEntry *fe = FindFontForStyle(
+                  (aMatchData->mStyle == nullptr) ? *aMatchData->mStyle : normal,
+                  needsBold);
+
+    if (fe && !fe->SkipDuringSystemFallback()) {
+        int32_t rank = 0;
+
+        if (fe->TestCharacterMap(aMatchData->mCh)) {
+            rank += RANK_MATCHED_CMAP;
+            aMatchData->mCount++;
+#ifdef PR_LOGGING
+            PRLogModuleInfo *log = gfxPlatform::GetLog(eGfxLog_textrun);
+
+            if (MOZ_UNLIKELY(PR_LOG_TEST(log, PR_LOG_DEBUG))) {
+                uint32_t unicodeRange = FindCharUnicodeRange(aMatchData->mCh);
+                uint32_t script = GetScriptCode(aMatchData->mCh);
+                PR_LOG(log, PR_LOG_DEBUG,\
+                       ("(textrun-systemfallback-fonts) char: u+%6.6x "
+                        "unicode-range: %d script: %d match: [%s]\n",
+                        aMatchData->mCh,
+                        unicodeRange, script,
+                        NS_ConvertUTF16toUTF8(fe->Name()).get()));
+            }
+#endif
+        }
+
+        aMatchData->mCmapsTested++;
+        if (rank == 0) {
+            return;
+        }
+
+         // omitting from original windows code -- family name, lang group, pitch
+         // not available in current FontEntry implementation
+        rank += CalcStyleMatch(fe, aMatchData->mStyle);
+
+        // xxx - add whether AAT font with morphing info for specific lang groups
+
+        if (rank > aMatchData->mMatchRank
+            || (rank == aMatchData->mMatchRank &&
+                Compare(fe->Name(), aMatchData->mBestMatch->Name()) > 0))
+        {
+            aMatchData->mBestMatch = fe;
+            aMatchData->mMatchedFamily = this;
+            aMatchData->mMatchRank = rank;
+        }
+    }
+}
+
+void
+gfxFontFamily::SearchAllFontsForChar(GlobalFontMatch *aMatchData)
+{
+    uint32_t i, numFonts = mAvailableFonts.Length();
+    for (i = 0; i < numFonts; i++) {
+        gfxFontEntry *fe = mAvailableFonts[i];
+        if (fe && fe->TestCharacterMap(aMatchData->mCh)) {
+            int32_t rank = RANK_MATCHED_CMAP;
+            rank += CalcStyleMatch(fe, aMatchData->mStyle);
+            if (rank > aMatchData->mMatchRank
+                || (rank == aMatchData->mMatchRank &&
+                    Compare(fe->Name(), aMatchData->mBestMatch->Name()) > 0))
+            {
+                aMatchData->mBestMatch = fe;
+                aMatchData->mMatchedFamily = this;
+                aMatchData->mMatchRank = rank;
+            }
+        }
+    }
+}
+
+/*static*/ void
+gfxFontFamily::ReadOtherFamilyNamesForFace(const nsAString& aFamilyName,
+                                           const char *aNameData,
+                                           uint32_t aDataLength,
+                                           nsTArray<nsString>& aOtherFamilyNames,
+                                           bool useFullName)
+{
+    const gfxFontUtils::NameHeader *nameHeader =
+        reinterpret_cast<const gfxFontUtils::NameHeader*>(aNameData);
+
+    uint32_t nameCount = nameHeader->count;
+    if (nameCount * sizeof(gfxFontUtils::NameRecord) > aDataLength) {
+        NS_WARNING("invalid font (name records)");
+        return;
+    }
+    
+    const gfxFontUtils::NameRecord *nameRecord =
+        reinterpret_cast<const gfxFontUtils::NameRecord*>(aNameData + sizeof(gfxFontUtils::NameHeader));
+    uint32_t stringsBase = uint32_t(nameHeader->stringOffset);
+
+    for (uint32_t i = 0; i < nameCount; i++, nameRecord++) {
+        uint32_t nameLen = nameRecord->length;
+        uint32_t nameOff = nameRecord->offset;  // offset from base of string storage
+
+        if (stringsBase + nameOff + nameLen > aDataLength) {
+            NS_WARNING("invalid font (name table strings)");
+            return;
+        }
+
+        uint16_t nameID = nameRecord->nameID;
+        if ((useFullName && nameID == gfxFontUtils::NAME_ID_FULL) ||
+            (!useFullName && (nameID == gfxFontUtils::NAME_ID_FAMILY ||
+                              nameID == gfxFontUtils::NAME_ID_PREFERRED_FAMILY))) {
+            nsAutoString otherFamilyName;
+            bool ok = gfxFontUtils::DecodeFontName(aNameData + stringsBase + nameOff,
+                                                     nameLen,
+                                                     uint32_t(nameRecord->platformID),
+                                                     uint32_t(nameRecord->encodingID),
+                                                     uint32_t(nameRecord->languageID),
+                                                     otherFamilyName);
+            // add if not same as canonical family name
+            if (ok && otherFamilyName != aFamilyName) {
+                aOtherFamilyNames.AppendElement(otherFamilyName);
+            }
+        }
+    }
+}
+
+// returns true if other names were found, false otherwise
+bool
+gfxFontFamily::ReadOtherFamilyNamesForFace(gfxPlatformFontList *aPlatformFontList,
+                                           hb_blob_t           *aNameTable,
+                                           bool                 useFullName)
+{
+    uint32_t dataLength;
+    const char *nameData = hb_blob_get_data(aNameTable, &dataLength);
+    nsAutoTArray<nsString,4> otherFamilyNames;
+
+    ReadOtherFamilyNamesForFace(mName, nameData, dataLength,
+                                otherFamilyNames, useFullName);
+
+    uint32_t n = otherFamilyNames.Length();
+    for (uint32_t i = 0; i < n; i++) {
+        aPlatformFontList->AddOtherFamilyName(this, otherFamilyNames[i]);
+    }
+
+    return n != 0;
+}
+
+void
+gfxFontFamily::ReadOtherFamilyNames(gfxPlatformFontList *aPlatformFontList)
+{
+    if (mOtherFamilyNamesInitialized) 
+        return;
+    mOtherFamilyNamesInitialized = true;
+
+    FindStyleVariations();
+
+    // read in other family names for the first face in the list
+    uint32_t i, numFonts = mAvailableFonts.Length();
+    const uint32_t kNAME = TRUETYPE_TAG('n','a','m','e');
+
+    for (i = 0; i < numFonts; ++i) {
+        gfxFontEntry *fe = mAvailableFonts[i];
+        if (!fe) {
+            continue;
+        }
+        gfxFontEntry::AutoTable nameTable(fe, kNAME);
+        if (!nameTable) {
+            continue;
+        }
+        mHasOtherFamilyNames = ReadOtherFamilyNamesForFace(aPlatformFontList,
+                                                           nameTable);
+        break;
+    }
+
+    // read in other names for the first face in the list with the assumption
+    // that if extra names don't exist in that face then they don't exist in
+    // other faces for the same font
+    if (!mHasOtherFamilyNames) 
+        return;
+
+    // read in names for all faces, needed to catch cases where fonts have
+    // family names for individual weights (e.g. Hiragino Kaku Gothic Pro W6)
+    for ( ; i < numFonts; i++) {
+        gfxFontEntry *fe = mAvailableFonts[i];
+        if (!fe) {
+            continue;
+        }
+        gfxFontEntry::AutoTable nameTable(fe, kNAME);
+        if (!nameTable) {
+            continue;
+        }
+        ReadOtherFamilyNamesForFace(aPlatformFontList, nameTable);
+    }
+}
+
+void
+gfxFontFamily::ReadFaceNames(gfxPlatformFontList *aPlatformFontList, 
+                             bool aNeedFullnamePostscriptNames,
+                             FontInfoData *aFontInfoData)
+{
+    // if all needed names have already been read, skip
+    if (mOtherFamilyNamesInitialized &&
+        (mFaceNamesInitialized || !aNeedFullnamePostscriptNames))
+        return;
+
+    bool asyncFontLoaderDisabled = false;
+
+#if defined(XP_MACOSX)
+    // bug 975460 - async font loader crashes sometimes under 10.6, disable
+    if (!nsCocoaFeatures::OnLionOrLater()) {
+        asyncFontLoaderDisabled = true;
+    }
+#endif
+
+    if (!mOtherFamilyNamesInitialized &&
+        aFontInfoData &&
+        aFontInfoData->mLoadOtherNames &&
+        !asyncFontLoaderDisabled)
+    {
+        nsAutoTArray<nsString,4> otherFamilyNames;
+        bool foundOtherNames =
+            aFontInfoData->GetOtherFamilyNames(mName, otherFamilyNames);
+        if (foundOtherNames) {
+            uint32_t i, n = otherFamilyNames.Length();
+            for (i = 0; i < n; i++) {
+                aPlatformFontList->AddOtherFamilyName(this, otherFamilyNames[i]);
+            }
+        }
+        mOtherFamilyNamesInitialized = true;
+    }
+
+    // if all needed data has been initialized, return
+    if (mOtherFamilyNamesInitialized &&
+        (mFaceNamesInitialized || !aNeedFullnamePostscriptNames)) {
+        return;
+    }
+
+    FindStyleVariations(aFontInfoData);
+
+    // check again, as style enumeration code may have loaded names
+    if (mOtherFamilyNamesInitialized &&
+        (mFaceNamesInitialized || !aNeedFullnamePostscriptNames)) {
+        return;
+    }
+
+    uint32_t i, numFonts = mAvailableFonts.Length();
+    const uint32_t kNAME = TRUETYPE_TAG('n','a','m','e');
+
+    bool firstTime = true, readAllFaces = false;
+    for (i = 0; i < numFonts; ++i) {
+        gfxFontEntry *fe = mAvailableFonts[i];
+        if (!fe) {
+            continue;
+        }
+
+        nsAutoString fullname, psname;
+        bool foundFaceNames = false;
+        if (!mFaceNamesInitialized &&
+            aNeedFullnamePostscriptNames &&
+            aFontInfoData &&
+            aFontInfoData->mLoadFaceNames) {
+            aFontInfoData->GetFaceNames(fe->Name(), fullname, psname);
+            if (!fullname.IsEmpty()) {
+                aPlatformFontList->AddFullname(fe, fullname);
+            }
+            if (!psname.IsEmpty()) {
+                aPlatformFontList->AddPostscriptName(fe, psname);
+            }
+            foundFaceNames = true;
+
+            // found everything needed? skip to next font
+            if (mOtherFamilyNamesInitialized) {
+                continue;
+            }
+        }
+
+        // load directly from the name table
+        gfxFontEntry::AutoTable nameTable(fe, kNAME);
+        if (!nameTable) {
+            continue;
+        }
+
+        if (aNeedFullnamePostscriptNames && !foundFaceNames) {
+            if (gfxFontUtils::ReadCanonicalName(
+                    nameTable, gfxFontUtils::NAME_ID_FULL, fullname) == NS_OK)
+            {
+                aPlatformFontList->AddFullname(fe, fullname);
+            }
+
+            if (gfxFontUtils::ReadCanonicalName(
+                    nameTable, gfxFontUtils::NAME_ID_POSTSCRIPT, psname) == NS_OK)
+            {
+                aPlatformFontList->AddPostscriptName(fe, psname);
+            }
+        }
+
+        if (!mOtherFamilyNamesInitialized && (firstTime || readAllFaces)) {
+            bool foundOtherName = ReadOtherFamilyNamesForFace(aPlatformFontList,
+                                                              nameTable);
+
+            // if the first face has a different name, scan all faces, otherwise
+            // assume the family doesn't have other names
+            if (firstTime && foundOtherName) {
+                mHasOtherFamilyNames = true;
+                readAllFaces = true;
+            }
+            firstTime = false;
+        }
+
+        // if not reading in any more names, skip other faces
+        if (!readAllFaces && !aNeedFullnamePostscriptNames) {
+            break;
+        }
+    }
+
+    mFaceNamesInitialized = true;
+    mOtherFamilyNamesInitialized = true;
+}
+
+
+gfxFontEntry*
+gfxFontFamily::FindFont(const nsAString& aPostscriptName)
+{
+    // find the font using a simple linear search
+    uint32_t numFonts = mAvailableFonts.Length();
+    for (uint32_t i = 0; i < numFonts; i++) {
+        gfxFontEntry *fe = mAvailableFonts[i].get();
+        if (fe && fe->Name() == aPostscriptName)
+            return fe;
+    }
+    return nullptr;
+}
+
+void
+gfxFontFamily::ReadAllCMAPs(FontInfoData *aFontInfoData)
+{
+    FindStyleVariations(aFontInfoData);
+
+    uint32_t i, numFonts = mAvailableFonts.Length();
+    for (i = 0; i < numFonts; i++) {
+        gfxFontEntry *fe = mAvailableFonts[i];
+        // don't try to load cmaps for downloadable fonts not yet loaded
+        if (!fe || fe->mIsProxy) {
+            continue;
+        }
+        fe->ReadCMAP(aFontInfoData);
+        mFamilyCharacterMap.Union(*(fe->mCharacterMap));
+    }
+    mFamilyCharacterMap.Compact();
+    mFamilyCharacterMapInitialized = true;
+}
+
+void
+gfxFontFamily::AddSizeOfExcludingThis(MallocSizeOf aMallocSizeOf,
+                                      FontListSizes* aSizes) const
+{
+    aSizes->mFontListSize +=
+        mName.SizeOfExcludingThisIfUnshared(aMallocSizeOf);
+    aSizes->mCharMapsSize +=
+        mFamilyCharacterMap.SizeOfExcludingThis(aMallocSizeOf);
+
+    aSizes->mFontListSize +=
+        mAvailableFonts.SizeOfExcludingThis(aMallocSizeOf);
+    for (uint32_t i = 0; i < mAvailableFonts.Length(); ++i) {
+        gfxFontEntry *fe = mAvailableFonts[i];
+        if (fe) {
+            fe->AddSizeOfIncludingThis(aMallocSizeOf, aSizes);
+        }
+    }
+}
+
+void
+gfxFontFamily::AddSizeOfIncludingThis(MallocSizeOf aMallocSizeOf,
+                                      FontListSizes* aSizes) const
+{
+    aSizes->mFontListSize += aMallocSizeOf(this);
+    AddSizeOfExcludingThis(aMallocSizeOf, aSizes);
+}
+
+/*
+ * gfxFontCache - global cache of gfxFont instances.
+ * Expires unused fonts after a short interval;
+ * notifies fonts to age their cached shaped-word records;
+ * observes memory-pressure notification and tells fonts to clear their
+ * shaped-word caches to free up memory.
+ */
+
+MOZ_DEFINE_MALLOC_SIZE_OF(FontCacheMallocSizeOf)
+
+NS_IMPL_ISUPPORTS(gfxFontCache::MemoryReporter, nsIMemoryReporter)
+
+NS_IMETHODIMP
+gfxFontCache::MemoryReporter::CollectReports
+    (nsIMemoryReporterCallback* aCb,
+     nsISupports* aClosure)
+{
+    FontCacheSizes sizes;
+
+    gfxFontCache::GetCache()->AddSizeOfIncludingThis(&FontCacheMallocSizeOf,
+                                                     &sizes);
+
+    aCb->Callback(EmptyCString(),
+                  NS_LITERAL_CSTRING("explicit/gfx/font-cache"),
+                  KIND_HEAP, UNITS_BYTES, sizes.mFontInstances,
+                  NS_LITERAL_CSTRING("Memory used for active font instances."),
+                  aClosure);
+
+    aCb->Callback(EmptyCString(),
+                  NS_LITERAL_CSTRING("explicit/gfx/font-shaped-words"),
+                  KIND_HEAP, UNITS_BYTES, sizes.mShapedWords,
+                  NS_LITERAL_CSTRING("Memory used to cache shaped glyph data."),
+                  aClosure);
+
+    return NS_OK;
+}
+
+NS_IMPL_ISUPPORTS(gfxFontCache::Observer, nsIObserver)
+
+NS_IMETHODIMP
+gfxFontCache::Observer::Observe(nsISupports *aSubject,
+                                const char *aTopic,
+                                const char16_t *someData)
+{
+    if (!nsCRT::strcmp(aTopic, "memory-pressure")) {
+        gfxFontCache *fontCache = gfxFontCache::GetCache();
+        if (fontCache) {
+            fontCache->FlushShapedWordCaches();
+        }
+    } else {
+        NS_NOTREACHED("unexpected notification topic");
+    }
+    return NS_OK;
+}
+
+nsresult
+gfxFontCache::Init()
+{
+    NS_ASSERTION(!gGlobalCache, "Where did this come from?");
+    gGlobalCache = new gfxFontCache();
+    if (!gGlobalCache) {
+        return NS_ERROR_OUT_OF_MEMORY;
+    }
+    RegisterStrongMemoryReporter(new MemoryReporter());
+    return NS_OK;
+}
+
+void
+gfxFontCache::Shutdown()
+{
+    delete gGlobalCache;
+    gGlobalCache = nullptr;
+
+#ifdef DEBUG_TEXT_RUN_STORAGE_METRICS
+    printf("Textrun storage high water mark=%d\n", gTextRunStorageHighWaterMark);
+    printf("Total number of fonts=%d\n", gFontCount);
+    printf("Total glyph extents allocated=%d (size %d)\n", gGlyphExtentsCount,
+            int(gGlyphExtentsCount*sizeof(gfxGlyphExtents)));
+    printf("Total glyph extents width-storage size allocated=%d\n", gGlyphExtentsWidthsTotalSize);
+    printf("Number of simple glyph extents eagerly requested=%d\n", gGlyphExtentsSetupEagerSimple);
+    printf("Number of tight glyph extents eagerly requested=%d\n", gGlyphExtentsSetupEagerTight);
+    printf("Number of tight glyph extents lazily requested=%d\n", gGlyphExtentsSetupLazyTight);
+    printf("Number of simple glyph extent setups that fell back to tight=%d\n", gGlyphExtentsSetupFallBackToTight);
+#endif
+}
+
+gfxFontCache::gfxFontCache()
+    : nsExpirationTracker<gfxFont,3>(FONT_TIMEOUT_SECONDS * 1000)
+{
+    nsCOMPtr<nsIObserverService> obs = GetObserverService();
+    if (obs) {
+        obs->AddObserver(new Observer, "memory-pressure", false);
+    }
+
+#ifndef RELEASE_BUILD
+    // Currently disabled for release builds, due to unexplained crashes
+    // during expiration; see bug 717175 & 894798.
+    mWordCacheExpirationTimer = do_CreateInstance("@mozilla.org/timer;1");
+    if (mWordCacheExpirationTimer) {
+        mWordCacheExpirationTimer->
+            InitWithFuncCallback(WordCacheExpirationTimerCallback, this,
+                                 SHAPED_WORD_TIMEOUT_SECONDS * 1000,
+                                 nsITimer::TYPE_REPEATING_SLACK);
+    }
+#endif
+}
+
+gfxFontCache::~gfxFontCache()
+{
+    // Ensure the user font cache releases its references to font entries,
+    // so they aren't kept alive after the font instances and font-list
+    // have been shut down.
+    gfxUserFontSet::UserFontCache::Shutdown();
+
+    if (mWordCacheExpirationTimer) {
+        mWordCacheExpirationTimer->Cancel();
+        mWordCacheExpirationTimer = nullptr;
+    }
+
+    // Expire everything that has a zero refcount, so we don't leak them.
+    AgeAllGenerations();
+    // All fonts should be gone.
+    NS_WARN_IF_FALSE(mFonts.Count() == 0,
+                     "Fonts still alive while shutting down gfxFontCache");
+    // Note that we have to delete everything through the expiration
+    // tracker, since there might be fonts not in the hashtable but in
+    // the tracker.
+}
+
+bool
+gfxFontCache::HashEntry::KeyEquals(const KeyTypePointer aKey) const
+{
+    return aKey->mFontEntry == mFont->GetFontEntry() &&
+           aKey->mStyle->Equals(*mFont->GetStyle());
+}
+
+already_AddRefed<gfxFont>
+gfxFontCache::Lookup(const gfxFontEntry *aFontEntry,
+                     const gfxFontStyle *aStyle)
+{
+    Key key(aFontEntry, aStyle);
+    HashEntry *entry = mFonts.GetEntry(key);
+
+    Telemetry::Accumulate(Telemetry::FONT_CACHE_HIT, entry != nullptr);
+    if (!entry)
+        return nullptr;
+
+    nsRefPtr<gfxFont> font = entry->mFont;
+    return font.forget();
+}
+
+void
+gfxFontCache::AddNew(gfxFont *aFont)
+{
+    Key key(aFont->GetFontEntry(), aFont->GetStyle());
+    HashEntry *entry = mFonts.PutEntry(key);
+    if (!entry)
+        return;
+    gfxFont *oldFont = entry->mFont;
+    entry->mFont = aFont;
+    // Assert that we can find the entry we just put in (this fails if the key
+    // has a NaN float value in it, e.g. 'sizeAdjust').
+    MOZ_ASSERT(entry == mFonts.GetEntry(key));
+    // If someone's asked us to replace an existing font entry, then that's a
+    // bit weird, but let it happen, and expire the old font if it's not used.
+    if (oldFont && oldFont->GetExpirationState()->IsTracked()) {
+        // if oldFont == aFont, recount should be > 0,
+        // so we shouldn't be here.
+        NS_ASSERTION(aFont != oldFont, "new font is tracked for expiry!");
+        NotifyExpired(oldFont);
+    }
+}
+
+void
+gfxFontCache::NotifyReleased(gfxFont *aFont)
+{
+    nsresult rv = AddObject(aFont);
+    if (NS_FAILED(rv)) {
+        // We couldn't track it for some reason. Kill it now.
+        DestroyFont(aFont);
+    }
+    // Note that we might have fonts that aren't in the hashtable, perhaps because
+    // of OOM adding to the hashtable or because someone did an AddNew where
+    // we already had a font. These fonts are added to the expiration tracker
+    // anyway, even though Lookup can't resurrect them. Eventually they will
+    // expire and be deleted.
+}
+
+void
+gfxFontCache::NotifyExpired(gfxFont *aFont)
+{
+    aFont->ClearCachedWords();
+    RemoveObject(aFont);
+    DestroyFont(aFont);
+}
+
+void
+gfxFontCache::DestroyFont(gfxFont *aFont)
+{
+    Key key(aFont->GetFontEntry(), aFont->GetStyle());
+    HashEntry *entry = mFonts.GetEntry(key);
+    if (entry && entry->mFont == aFont) {
+        mFonts.RemoveEntry(key);
+    }
+    NS_ASSERTION(aFont->GetRefCount() == 0,
+                 "Destroying with non-zero ref count!");
+    delete aFont;
+}
+
+/*static*/
+PLDHashOperator
+gfxFontCache::AgeCachedWordsForFont(HashEntry* aHashEntry, void* aUserData)
+{
+    aHashEntry->mFont->AgeCachedWords();
+    return PL_DHASH_NEXT;
+}
+
+/*static*/
+void
+gfxFontCache::WordCacheExpirationTimerCallback(nsITimer* aTimer, void* aCache)
+{
+    gfxFontCache* cache = static_cast<gfxFontCache*>(aCache);
+    cache->mFonts.EnumerateEntries(AgeCachedWordsForFont, nullptr);
+}
+
+/*static*/
+PLDHashOperator
+gfxFontCache::ClearCachedWordsForFont(HashEntry* aHashEntry, void* aUserData)
+{
+    aHashEntry->mFont->ClearCachedWords();
+    return PL_DHASH_NEXT;
+}
+
+/*static*/
+size_t
+gfxFontCache::AddSizeOfFontEntryExcludingThis(HashEntry* aHashEntry,
+                                              MallocSizeOf aMallocSizeOf,
+                                              void* aUserArg)
+{
+    HashEntry *entry = static_cast<HashEntry*>(aHashEntry);
+    FontCacheSizes *sizes = static_cast<FontCacheSizes*>(aUserArg);
+    entry->mFont->AddSizeOfExcludingThis(aMallocSizeOf, sizes);
+
+    // The entry's size is recorded in the |sizes| parameter, so we return zero
+    // here to the hashtable enumerator.
+    return 0;
+}
+
+void
+gfxFontCache::AddSizeOfExcludingThis(MallocSizeOf aMallocSizeOf,
+                                     FontCacheSizes* aSizes) const
+{
+    // TODO: add the overhead of the expiration tracker (generation arrays)
+
+    aSizes->mFontInstances +=
+        mFonts.SizeOfExcludingThis(AddSizeOfFontEntryExcludingThis,
+                                   aMallocSizeOf, aSizes);
+}
+
+void
+gfxFontCache::AddSizeOfIncludingThis(MallocSizeOf aMallocSizeOf,
+                                     FontCacheSizes* aSizes) const
+{
+    aSizes->mFontInstances += aMallocSizeOf(this);
+    AddSizeOfExcludingThis(aMallocSizeOf, aSizes);
+}
+
+#define MAX_SSXX_VALUE 99
+#define MAX_CVXX_VALUE 99
+
+static void
+LookupAlternateValues(gfxFontFeatureValueSet *featureLookup,
+                      const nsAString& aFamily,
+                      const nsTArray<gfxAlternateValue>& altValue,
+                      nsTArray<gfxFontFeature>& aFontFeatures)
+{
+    uint32_t numAlternates = altValue.Length();
+    for (uint32_t i = 0; i < numAlternates; i++) {
+        const gfxAlternateValue& av = altValue.ElementAt(i);
+        nsAutoTArray<uint32_t,4> values;
+
+        // map <family, name, feature> ==> <values>
+        bool found =
+            featureLookup->GetFontFeatureValuesFor(aFamily, av.alternate,
+                                                   av.value, values);
+        uint32_t numValues = values.Length();
+
+        // nothing defined, skip
+        if (!found || numValues == 0) {
+            continue;
+        }
+
+        gfxFontFeature feature;
+        if (av.alternate == NS_FONT_VARIANT_ALTERNATES_CHARACTER_VARIANT) {
+            NS_ASSERTION(numValues <= 2,
+                         "too many values allowed for character-variant");
+            // character-variant(12 3) ==> 'cv12' = 3
+            uint32_t nn = values.ElementAt(0);
+            // ignore values greater than 99
+            if (nn == 0 || nn > MAX_CVXX_VALUE) {
+                continue;
+            }
+            feature.mValue = 1;
+            if (numValues > 1) {
+                feature.mValue = values.ElementAt(1);
+            }
+            feature.mTag = HB_TAG('c','v',('0' + nn / 10), ('0' + nn % 10));
+            aFontFeatures.AppendElement(feature);
+
+        } else if (av.alternate == NS_FONT_VARIANT_ALTERNATES_STYLESET) {
+            // styleset(1 2 7) ==> 'ss01' = 1, 'ss02' = 1, 'ss07' = 1
+            feature.mValue = 1;
+            for (uint32_t v = 0; v < numValues; v++) {
+                uint32_t nn = values.ElementAt(v);
+                if (nn == 0 || nn > MAX_SSXX_VALUE) {
+                    continue;
+                }
+                feature.mTag = HB_TAG('s','s',('0' + nn / 10), ('0' + nn % 10));
+                aFontFeatures.AppendElement(feature);
+            }
+
+        } else {
+            NS_ASSERTION(numValues == 1,
+                   "too many values for font-specific font-variant-alternates");
+            feature.mValue = values.ElementAt(0);
+
+            switch (av.alternate) {
+                case NS_FONT_VARIANT_ALTERNATES_STYLISTIC:  // salt
+                    feature.mTag = HB_TAG('s','a','l','t');
+                    break;
+                case NS_FONT_VARIANT_ALTERNATES_SWASH:  // swsh, cswh
+                    feature.mTag = HB_TAG('s','w','s','h');
+                    aFontFeatures.AppendElement(feature);
+                    feature.mTag = HB_TAG('c','s','w','h');
+                    break;
+                case NS_FONT_VARIANT_ALTERNATES_ORNAMENTS: // ornm
+                    feature.mTag = HB_TAG('o','r','n','m');
+                    break;
+                case NS_FONT_VARIANT_ALTERNATES_ANNOTATION: // nalt
+                    feature.mTag = HB_TAG('n','a','l','t');
+                    break;
+                default:
+                    feature.mTag = 0;
+                    break;
+            }
+
+            NS_ASSERTION(feature.mTag, "unsupported alternate type");
+            if (!feature.mTag) {
+                continue;
+            }
+            aFontFeatures.AppendElement(feature);
+        }
+    }
+}
+
+/* static */ bool
+gfxFontShaper::MergeFontFeatures(
+    const gfxFontStyle *aStyle,
+    const nsTArray<gfxFontFeature>& aFontFeatures,
+    bool aDisableLigatures,
+    const nsAString& aFamilyName,
+    nsDataHashtable<nsUint32HashKey,uint32_t>& aMergedFeatures)
+{
+    uint32_t numAlts = aStyle->alternateValues.Length();
+    const nsTArray<gfxFontFeature>& styleRuleFeatures =
+        aStyle->featureSettings;
+
+    // bail immediately if nothing to do
+    if (styleRuleFeatures.IsEmpty() &&
+        aFontFeatures.IsEmpty() &&
+        !aDisableLigatures &&
+        numAlts == 0) {
+        return false;
+    }
+
+    // Ligature features are enabled by default in the generic shaper,
+    // so we explicitly turn them off if necessary (for letter-spacing)
+    if (aDisableLigatures) {
+        aMergedFeatures.Put(HB_TAG('l','i','g','a'), 0);
+        aMergedFeatures.Put(HB_TAG('c','l','i','g'), 0);
+    }
+
+    // add feature values from font
+    uint32_t i, count;
+
+    count = aFontFeatures.Length();
+    for (i = 0; i < count; i++) {
+        const gfxFontFeature& feature = aFontFeatures.ElementAt(i);
+        aMergedFeatures.Put(feature.mTag, feature.mValue);
+    }
+
+    // add font-specific feature values from style rules
+    if (aStyle->featureValueLookup && numAlts > 0) {
+        nsAutoTArray<gfxFontFeature,4> featureList;
+
+        // insert list of alternate feature settings
+        LookupAlternateValues(aStyle->featureValueLookup, aFamilyName,
+                              aStyle->alternateValues, featureList);
+
+        count = featureList.Length();
+        for (i = 0; i < count; i++) {
+            const gfxFontFeature& feature = featureList.ElementAt(i);
+            aMergedFeatures.Put(feature.mTag, feature.mValue);
+        }
+    }
+
+    // add feature values from style rules
+    count = styleRuleFeatures.Length();
+    for (i = 0; i < count; i++) {
+        const gfxFontFeature& feature = styleRuleFeatures.ElementAt(i);
+        aMergedFeatures.Put(feature.mTag, feature.mValue);
+    }
+
+    return aMergedFeatures.Count() != 0;
+}
+
+void
+gfxFont::RunMetrics::CombineWith(const RunMetrics& aOther, bool aOtherIsOnLeft)
+{
+    mAscent = std::max(mAscent, aOther.mAscent);
+    mDescent = std::max(mDescent, aOther.mDescent);
+    if (aOtherIsOnLeft) {
+        mBoundingBox =
+            (mBoundingBox + gfxPoint(aOther.mAdvanceWidth, 0)).Union(aOther.mBoundingBox);
+    } else {
+        mBoundingBox =
+            mBoundingBox.Union(aOther.mBoundingBox + gfxPoint(mAdvanceWidth, 0));
+    }
+    mAdvanceWidth += aOther.mAdvanceWidth;
+}
+
+gfxFont::gfxFont(gfxFontEntry *aFontEntry, const gfxFontStyle *aFontStyle,
+                 AntialiasOption anAAOption, cairo_scaled_font_t *aScaledFont) :
+    mScaledFont(aScaledFont),
+    mFontEntry(aFontEntry), mIsValid(true),
+    mApplySyntheticBold(false),
+    mStyle(*aFontStyle),
+    mAdjustedSize(0.0),
+    mFUnitsConvFactor(0.0f),
+    mAntialiasOption(anAAOption)
+{
+#ifdef DEBUG_TEXT_RUN_STORAGE_METRICS
+    ++gFontCount;
+#endif
+    mKerningSet = HasFeatureSet(HB_TAG('k','e','r','n'), mKerningEnabled);
+}
+
+static PLDHashOperator
+NotifyFontDestroyed(nsPtrHashKey<gfxFont::GlyphChangeObserver>* aKey,
+                    void* aClosure)
+{
+    aKey->GetKey()->ForgetFont();
+    return PL_DHASH_NEXT;
+}
+
+gfxFont::~gfxFont()
+{
+    uint32_t i, count = mGlyphExtentsArray.Length();
+    // We destroy the contents of mGlyphExtentsArray explicitly instead of
+    // using nsAutoPtr because VC++ can't deal with nsTArrays of nsAutoPtrs
+    // of classes that lack a proper copy constructor
+    for (i = 0; i < count; ++i) {
+        delete mGlyphExtentsArray[i];
+    }
+
+    mFontEntry->NotifyFontDestroyed(this);
+
+    if (mGlyphChangeObservers) {
+        mGlyphChangeObservers->EnumerateEntries(NotifyFontDestroyed, nullptr);
+    }
+}
+
+gfxFloat
+gfxFont::GetGlyphHAdvance(gfxContext *aCtx, uint16_t aGID)
+{
+    if (!SetupCairoFont(aCtx)) {
+        return 0;
+    }
+    if (ProvidesGlyphWidths()) {
+        return GetGlyphWidth(aCtx, aGID) / 65536.0;
+    }
+    if (mFUnitsConvFactor == 0.0f) {
+        GetMetrics();
+    }
+    NS_ASSERTION(mFUnitsConvFactor > 0.0f,
+                 "missing font unit conversion factor");
+    if (!mHarfBuzzShaper) {
+        mHarfBuzzShaper = new gfxHarfBuzzShaper(this);
+    }
+    gfxHarfBuzzShaper* shaper =
+        static_cast<gfxHarfBuzzShaper*>(mHarfBuzzShaper.get());
+    if (!shaper->Initialize()) {
+        return 0;
+    }
+    return shaper->GetGlyphHAdvance(aCtx, aGID) / 65536.0;
+}
+
+/*static*/
+PLDHashOperator
+gfxFont::AgeCacheEntry(CacheHashEntry *aEntry, void *aUserData)
+{
+    if (!aEntry->mShapedWord) {
+        NS_ASSERTION(aEntry->mShapedWord, "cache entry has no gfxShapedWord!");
+        return PL_DHASH_REMOVE;
+    }
+    if (aEntry->mShapedWord->IncrementAge() == kShapedWordCacheMaxAge) {
+        return PL_DHASH_REMOVE;
+    }
+    return PL_DHASH_NEXT;
+}
+
+static void
+CollectLookupsByFeature(hb_face_t *aFace, hb_tag_t aTableTag,
+                        uint32_t aFeatureIndex, hb_set_t *aLookups)
+{
+    uint32_t lookups[32];
+    uint32_t i, len, offset;
+
+    offset = 0;
+    do {
+        len = ArrayLength(lookups);
+        hb_ot_layout_feature_get_lookups(aFace, aTableTag, aFeatureIndex,
+                                         offset, &len, lookups);
+        for (i = 0; i < len; i++) {
+            hb_set_add(aLookups, lookups[i]);
+        }
+        offset += len;
+    } while (len == ArrayLength(lookups));
+}
+
+static void
+CollectLookupsByLanguage(hb_face_t *aFace, hb_tag_t aTableTag,
+                         const nsTHashtable<nsUint32HashKey>&
+                             aSpecificFeatures,
+                         hb_set_t *aOtherLookups,
+                         hb_set_t *aSpecificFeatureLookups,
+                         uint32_t aScriptIndex, uint32_t aLangIndex)
+{
+    uint32_t reqFeatureIndex;
+    if (hb_ot_layout_language_get_required_feature_index(aFace, aTableTag,
+                                                         aScriptIndex,
+                                                         aLangIndex,
+                                                         &reqFeatureIndex)) {
+        CollectLookupsByFeature(aFace, aTableTag, reqFeatureIndex,
+                                aOtherLookups);
+    }
+
+    uint32_t featureIndexes[32];
+    uint32_t i, len, offset;
+
+    offset = 0;
+    do {
+        len = ArrayLength(featureIndexes);
+        hb_ot_layout_language_get_feature_indexes(aFace, aTableTag,
+                                                  aScriptIndex, aLangIndex,
+                                                  offset, &len, featureIndexes);
+
+        for (i = 0; i < len; i++) {
+            uint32_t featureIndex = featureIndexes[i];
+
+            // get the feature tag
+            hb_tag_t featureTag;
+            uint32_t tagLen = 1;
+            hb_ot_layout_language_get_feature_tags(aFace, aTableTag,
+                                                   aScriptIndex, aLangIndex,
+                                                   offset + i, &tagLen,
+                                                   &featureTag);
+
+            // collect lookups
+            hb_set_t *lookups = aSpecificFeatures.GetEntry(featureTag) ?
+                                    aSpecificFeatureLookups : aOtherLookups;
+            CollectLookupsByFeature(aFace, aTableTag, featureIndex, lookups);
+        }
+        offset += len;
+    } while (len == ArrayLength(featureIndexes));
+}
+
+static bool
+HasLookupRuleWithGlyphByScript(hb_face_t *aFace, hb_tag_t aTableTag,
+                               hb_tag_t aScriptTag, uint32_t aScriptIndex,
+                               uint16_t aGlyph,
+                               const nsTHashtable<nsUint32HashKey>&
+                                   aDefaultFeatures,
+                               bool& aHasDefaultFeatureWithGlyph)
+{
+    uint32_t numLangs, lang;
+    hb_set_t *defaultFeatureLookups = hb_set_create();
+    hb_set_t *nonDefaultFeatureLookups = hb_set_create();
+
+    // default lang
+    CollectLookupsByLanguage(aFace, aTableTag, aDefaultFeatures,
+                             nonDefaultFeatureLookups, defaultFeatureLookups,
+                             aScriptIndex,
+                             HB_OT_LAYOUT_DEFAULT_LANGUAGE_INDEX);
+
+    // iterate over langs
+    numLangs = hb_ot_layout_script_get_language_tags(aFace, aTableTag,
+                                                     aScriptIndex, 0,
+                                                     nullptr, nullptr);
+    for (lang = 0; lang < numLangs; lang++) {
+        CollectLookupsByLanguage(aFace, aTableTag, aDefaultFeatures,
+                                 nonDefaultFeatureLookups,
+                                 defaultFeatureLookups,
+                                 aScriptIndex, lang);
+    }
+
+    // look for the glyph among default feature lookups
+    aHasDefaultFeatureWithGlyph = false;
+    hb_set_t *glyphs = hb_set_create();
+    hb_codepoint_t index = -1;
+    while (hb_set_next(defaultFeatureLookups, &index)) {
+        hb_ot_layout_lookup_collect_glyphs(aFace, aTableTag, index,
+                                           glyphs, glyphs, glyphs,
+                                           glyphs);
+        if (hb_set_has(glyphs, aGlyph)) {
+            aHasDefaultFeatureWithGlyph = true;
+            break;
+        }
+    }
+
+    // look for the glyph among non-default feature lookups
+    // if no default feature lookups contained spaces
+    bool hasNonDefaultFeatureWithGlyph = false;
+    if (!aHasDefaultFeatureWithGlyph) {
+        hb_set_clear(glyphs);
+        index = -1;
+        while (hb_set_next(nonDefaultFeatureLookups, &index)) {
+            hb_ot_layout_lookup_collect_glyphs(aFace, aTableTag, index,
+                                               glyphs, glyphs, glyphs,
+                                               glyphs);
+            if (hb_set_has(glyphs, aGlyph)) {
+                hasNonDefaultFeatureWithGlyph = true;
+                break;
+            }
+        }
+    }
+
+    hb_set_destroy(glyphs);
+    hb_set_destroy(defaultFeatureLookups);
+    hb_set_destroy(nonDefaultFeatureLookups);
+
+    return aHasDefaultFeatureWithGlyph || hasNonDefaultFeatureWithGlyph;
+}
+
+static void
+HasLookupRuleWithGlyph(hb_face_t *aFace, hb_tag_t aTableTag, bool& aHasGlyph,
+                       hb_tag_t aSpecificFeature, bool& aHasGlyphSpecific,
+                       uint16_t aGlyph)
+{
+    // iterate over the scripts in the font
+    uint32_t numScripts, numLangs, script, lang;
+    hb_set_t *otherLookups = hb_set_create();
+    hb_set_t *specificFeatureLookups = hb_set_create();
+    nsTHashtable<nsUint32HashKey> specificFeature;
+
+    specificFeature.PutEntry(aSpecificFeature);
+
+    numScripts = hb_ot_layout_table_get_script_tags(aFace, aTableTag, 0,
+                                                    nullptr, nullptr);
+
+    for (script = 0; script < numScripts; script++) {
+        // default lang
+        CollectLookupsByLanguage(aFace, aTableTag, specificFeature,
+                                 otherLookups, specificFeatureLookups,
+                                 script, HB_OT_LAYOUT_DEFAULT_LANGUAGE_INDEX);
+
+        // iterate over langs
+        numLangs = hb_ot_layout_script_get_language_tags(aFace, HB_OT_TAG_GPOS,
+                                                         script, 0,
+                                                         nullptr, nullptr);
+        for (lang = 0; lang < numLangs; lang++) {
+            CollectLookupsByLanguage(aFace, aTableTag, specificFeature,
+                                     otherLookups, specificFeatureLookups,
+                                     script, lang);
+        }
+    }
+
+    // look for the glyph among non-specific feature lookups
+    hb_set_t *glyphs = hb_set_create();
+    hb_codepoint_t index = -1;
+    while (hb_set_next(otherLookups, &index)) {
+        hb_ot_layout_lookup_collect_glyphs(aFace, aTableTag, index,
+                                           glyphs, glyphs, glyphs,
+                                           glyphs);
+        if (hb_set_has(glyphs, aGlyph)) {
+            aHasGlyph = true;
+            break;
+        }
+    }
+
+    // look for the glyph among specific feature lookups
+    hb_set_clear(glyphs);
+    index = -1;
+    while (hb_set_next(specificFeatureLookups, &index)) {
+        hb_ot_layout_lookup_collect_glyphs(aFace, aTableTag, index,
+                                           glyphs, glyphs, glyphs,
+                                           glyphs);
+        if (hb_set_has(glyphs, aGlyph)) {
+            aHasGlyphSpecific = true;
+            break;
+        }
+    }
+
+    hb_set_destroy(glyphs);
+    hb_set_destroy(specificFeatureLookups);
+    hb_set_destroy(otherLookups);
+}
+
+nsDataHashtable<nsUint32HashKey, int32_t> *gfxFont::sScriptTagToCode = nullptr;
+nsTHashtable<nsUint32HashKey>             *gfxFont::sDefaultFeatures = nullptr;
+
+static inline bool
+HasSubstitution(uint32_t *aBitVector, uint32_t aBit) {
+    return (aBitVector[aBit >> 5] & (1 << (aBit & 0x1f))) != 0;
+}
+
+// union of all default substitution features across scripts
+static const hb_tag_t defaultFeatures[] = {
+    HB_TAG('a','b','v','f'),
+    HB_TAG('a','b','v','s'),
+    HB_TAG('a','k','h','n'),
+    HB_TAG('b','l','w','f'),
+    HB_TAG('b','l','w','s'),
+    HB_TAG('c','a','l','t'),
+    HB_TAG('c','c','m','p'),
+    HB_TAG('c','f','a','r'),
+    HB_TAG('c','j','c','t'),
+    HB_TAG('c','l','i','g'),
+    HB_TAG('f','i','n','2'),
+    HB_TAG('f','i','n','3'),
+    HB_TAG('f','i','n','a'),
+    HB_TAG('h','a','l','f'),
+    HB_TAG('h','a','l','n'),
+    HB_TAG('i','n','i','t'),
+    HB_TAG('i','s','o','l'),
+    HB_TAG('l','i','g','a'),
+    HB_TAG('l','j','m','o'),
+    HB_TAG('l','o','c','l'),
+    HB_TAG('l','t','r','a'),
+    HB_TAG('l','t','r','m'),
+    HB_TAG('m','e','d','2'),
+    HB_TAG('m','e','d','i'),
+    HB_TAG('m','s','e','t'),
+    HB_TAG('n','u','k','t'),
+    HB_TAG('p','r','e','f'),
+    HB_TAG('p','r','e','s'),
+    HB_TAG('p','s','t','f'),
+    HB_TAG('p','s','t','s'),
+    HB_TAG('r','c','l','t'),
+    HB_TAG('r','l','i','g'),
+    HB_TAG('r','k','r','f'),
+    HB_TAG('r','p','h','f'),
+    HB_TAG('r','t','l','a'),
+    HB_TAG('r','t','l','m'),
+    HB_TAG('t','j','m','o'),
+    HB_TAG('v','a','t','u'),
+    HB_TAG('v','e','r','t'),
+    HB_TAG('v','j','m','o')
+};
+
+void
+gfxFont::CheckForFeaturesInvolvingSpace()
+{
+    mFontEntry->mHasSpaceFeaturesInitialized = true;
+
+#ifdef PR_LOGGING
+    bool log = LOG_FONTINIT_ENABLED();
+    TimeStamp start;
+    if (MOZ_UNLIKELY(log)) {
+        start = TimeStamp::Now();
+    }
+#endif
+
+    bool result = false;
+
+    uint32_t spaceGlyph = GetSpaceGlyph();
+    if (!spaceGlyph) {
+        return;
+    }
+
+    hb_face_t *face = GetFontEntry()->GetHBFace();
+
+    // GSUB lookups - examine per script
+    if (hb_ot_layout_has_substitution(face)) {
+
+        // set up the script ==> code hashtable if needed
+        if (!sScriptTagToCode) {
+            sScriptTagToCode =
+                new nsDataHashtable<nsUint32HashKey,
+                                    int32_t>(MOZ_NUM_SCRIPT_CODES);
+            sScriptTagToCode->Put(HB_TAG('D','F','L','T'), MOZ_SCRIPT_COMMON);
+            for (int32_t s = MOZ_SCRIPT_ARABIC; s < MOZ_NUM_SCRIPT_CODES; s++) {
+                hb_script_t scriptTag = hb_script_t(GetScriptTagForCode(s));
+                hb_tag_t s1, s2;
+                hb_ot_tags_from_script(scriptTag, &s1, &s2);
+                sScriptTagToCode->Put(s1, s);
+                if (s2 != HB_OT_TAG_DEFAULT_SCRIPT) {
+                    sScriptTagToCode->Put(s2, s);
+                }
+            }
+
+            uint32_t numDefaultFeatures = ArrayLength(defaultFeatures);
+            sDefaultFeatures =
+                new nsTHashtable<nsUint32HashKey>(numDefaultFeatures);
+            for (uint32_t i = 0; i < numDefaultFeatures; i++) {
+                sDefaultFeatures->PutEntry(defaultFeatures[i]);
+            }
+        }
+
+        // iterate over the scripts in the font
+        hb_tag_t scriptTags[8];
+
+        uint32_t len, offset = 0;
+        do {
+            len = ArrayLength(scriptTags);
+            hb_ot_layout_table_get_script_tags(face, HB_OT_TAG_GSUB, offset,
+                                               &len, scriptTags);
+            for (uint32_t i = 0; i < len; i++) {
+                bool isDefaultFeature = false;
+                int32_t s;
+                if (!HasLookupRuleWithGlyphByScript(face, HB_OT_TAG_GSUB,
+                                                    scriptTags[i], offset + i,
+                                                    spaceGlyph,
+                                                    *sDefaultFeatures,
+                                                    isDefaultFeature) ||
+                    !sScriptTagToCode->Get(scriptTags[i], &s))
+                {
+                    continue;
+                }
+                result = true;
+                uint32_t index = s >> 5;
+                uint32_t bit = s & 0x1f;
+                if (isDefaultFeature) {
+                    mFontEntry->mDefaultSubSpaceFeatures[index] |= (1 << bit);
+                } else {
+                    mFontEntry->mNonDefaultSubSpaceFeatures[index] |= (1 << bit);
+                }
+            }
+            offset += len;
+        } while (len == ArrayLength(scriptTags));
+    }
+
+    // spaces in default features of default script?
+    // ==> can't use word cache, skip GPOS analysis
+    bool canUseWordCache = true;
+    if (HasSubstitution(mFontEntry->mDefaultSubSpaceFeatures,
+                        MOZ_SCRIPT_COMMON)) {
+        canUseWordCache = false;
+    }
+
+    // GPOS lookups - distinguish kerning from non-kerning features
+    mFontEntry->mHasSpaceFeaturesKerning = false;
+    mFontEntry->mHasSpaceFeaturesNonKerning = false;
+
+    if (canUseWordCache && hb_ot_layout_has_positioning(face)) {
+        bool hasKerning = false, hasNonKerning = false;
+        HasLookupRuleWithGlyph(face, HB_OT_TAG_GPOS, hasNonKerning,
+                               HB_TAG('k','e','r','n'), hasKerning, spaceGlyph);
+        if (hasKerning || hasNonKerning) {
+            result = true;
+        }
+        mFontEntry->mHasSpaceFeaturesKerning = hasKerning;
+        mFontEntry->mHasSpaceFeaturesNonKerning = hasNonKerning;
+    }
+
+    hb_face_destroy(face);
+    mFontEntry->mHasSpaceFeatures = result;
+
+#ifdef PR_LOGGING
+    if (MOZ_UNLIKELY(log)) {
+        TimeDuration elapsed = TimeStamp::Now() - start;
+        LOG_FONTINIT((
+            "(fontinit-spacelookups) font: %s - "
+            "subst default: %8.8x %8.8x %8.8x %8.8x "
+            "subst non-default: %8.8x %8.8x %8.8x %8.8x "
+            "kerning: %s non-kerning: %s time: %6.3f\n",
+            NS_ConvertUTF16toUTF8(mFontEntry->Name()).get(),
+            mFontEntry->mDefaultSubSpaceFeatures[3],
+            mFontEntry->mDefaultSubSpaceFeatures[2],
+            mFontEntry->mDefaultSubSpaceFeatures[1],
+            mFontEntry->mDefaultSubSpaceFeatures[0],
+            mFontEntry->mNonDefaultSubSpaceFeatures[3],
+            mFontEntry->mNonDefaultSubSpaceFeatures[2],
+            mFontEntry->mNonDefaultSubSpaceFeatures[1],
+            mFontEntry->mNonDefaultSubSpaceFeatures[0],
+            (mFontEntry->mHasSpaceFeaturesKerning ? "true" : "false"),
+            (mFontEntry->mHasSpaceFeaturesNonKerning ? "true" : "false"),
+            elapsed.ToMilliseconds()
+        ));
+    }
+#endif
+}
+
+bool
+gfxFont::HasSubstitutionRulesWithSpaceLookups(int32_t aRunScript)
+{
+    NS_ASSERTION(GetFontEntry()->mHasSpaceFeaturesInitialized,
+                 "need to initialize space lookup flags");
+    NS_ASSERTION(aRunScript < MOZ_NUM_SCRIPT_CODES, "weird script code");
+    if (aRunScript == MOZ_SCRIPT_INVALID ||
+        aRunScript >= MOZ_NUM_SCRIPT_CODES) {
+        return false;
+    }
+
+    // default features have space lookups ==> true
+    if (HasSubstitution(mFontEntry->mDefaultSubSpaceFeatures,
+                        MOZ_SCRIPT_COMMON) ||
+        HasSubstitution(mFontEntry->mDefaultSubSpaceFeatures,
+                        aRunScript))
+    {
+        return true;
+    }
+
+    // non-default features have space lookups and some type of
+    // font feature, in font or style is specified ==> true
+    if ((HasSubstitution(mFontEntry->mNonDefaultSubSpaceFeatures,
+                         MOZ_SCRIPT_COMMON) ||
+         HasSubstitution(mFontEntry->mNonDefaultSubSpaceFeatures,
+                         aRunScript)) &&
+        (!mStyle.featureSettings.IsEmpty() ||
+         !mFontEntry->mFeatureSettings.IsEmpty()))
+    {
+        return true;
+    }
+
+    return false;
+}
+
+bool
+gfxFont::SpaceMayParticipateInShaping(int32_t aRunScript)
+{
+    // avoid checking fonts known not to include default space-dependent features
+    if (MOZ_UNLIKELY(mFontEntry->mSkipDefaultFeatureSpaceCheck)) {
+        if (!mKerningSet && mStyle.featureSettings.IsEmpty() &&
+            mFontEntry->mFeatureSettings.IsEmpty()) {
+            return false;
+        }
+    }
+
+    // We record the presence of space-dependent features in the font entry
+    // so that subsequent instantiations for the same font face won't
+    // require us to re-check the tables; however, the actual check is done
+    // by gfxFont because not all font entry subclasses know how to create
+    // a harfbuzz face for introspection.
+    if (!mFontEntry->mHasSpaceFeaturesInitialized) {
+        CheckForFeaturesInvolvingSpace();
+    }
+
+    if (!mFontEntry->mHasSpaceFeatures) {
+        return false;
+    }
+
+    // if font has substitution rules or non-kerning positioning rules
+    // that involve spaces, bypass
+    if (HasSubstitutionRulesWithSpaceLookups(aRunScript) ||
+        mFontEntry->mHasSpaceFeaturesNonKerning) {
+        return true;
+    }
+
+    // if kerning explicitly enabled/disabled via font-feature-settings or
+    // font-kerning and kerning rules use spaces, only bypass when enabled
+    if (mKerningSet && mFontEntry->mHasSpaceFeaturesKerning) {
+        return mKerningEnabled;
+    }
+
+    return false;
+}
+
+bool
+gfxFont::HasFeatureSet(uint32_t aFeature, bool& aFeatureOn)
+{
+    aFeatureOn = false;
+
+    if (mStyle.featureSettings.IsEmpty() &&
+        GetFontEntry()->mFeatureSettings.IsEmpty()) {
+        return false;
+    }
+
+    // add feature values from font
+    bool featureSet = false;
+    uint32_t i, count;
+
+    nsTArray<gfxFontFeature>& fontFeatures = GetFontEntry()->mFeatureSettings;
+    count = fontFeatures.Length();
+    for (i = 0; i < count; i++) {
+        const gfxFontFeature& feature = fontFeatures.ElementAt(i);
+        if (feature.mTag == aFeature) {
+            featureSet = true;
+            aFeatureOn = (feature.mValue != 0);
+        }
+    }
+
+    // add feature values from style rules
+    nsTArray<gfxFontFeature>& styleFeatures = mStyle.featureSettings;
+    count = styleFeatures.Length();
+    for (i = 0; i < count; i++) {
+        const gfxFontFeature& feature = styleFeatures.ElementAt(i);
+        if (feature.mTag == aFeature) {
+            featureSet = true;
+            aFeatureOn = (feature.mValue != 0);
+        }
+    }
+
+    return featureSet;
+}
+
+/**
+ * A helper function in case we need to do any rounding or other
+ * processing here.
+ */
+#define ToDeviceUnits(aAppUnits, aDevUnitsPerAppUnit) \
+    (double(aAppUnits)*double(aDevUnitsPerAppUnit))
+
+struct GlyphBuffer {
+#define GLYPH_BUFFER_SIZE (2048/sizeof(cairo_glyph_t))
+    cairo_glyph_t mGlyphBuffer[GLYPH_BUFFER_SIZE];
+    unsigned int mNumGlyphs;
+
+    GlyphBuffer()
+        : mNumGlyphs(0) { }
+
+    cairo_glyph_t *AppendGlyph() {
+        return &mGlyphBuffer[mNumGlyphs++];
+    }
+
+    void Flush(cairo_t *aCR, DrawMode aDrawMode, bool aReverse,
+               gfxTextContextPaint *aContextPaint,
+               const gfxMatrix& aGlobalMatrix, bool aFinish = false) {
+        // Ensure there's enough room for a glyph to be added to the buffer
+        // and we actually have glyphs to draw
+        if ((!aFinish && mNumGlyphs < GLYPH_BUFFER_SIZE) || !mNumGlyphs) {
+            return;
+        }
+
+        if (aReverse) {
+            for (uint32_t i = 0; i < mNumGlyphs/2; ++i) {
+                cairo_glyph_t tmp = mGlyphBuffer[i];
+                mGlyphBuffer[i] = mGlyphBuffer[mNumGlyphs - 1 - i];
+                mGlyphBuffer[mNumGlyphs - 1 - i] = tmp;
+            }
+        }
+
+        if (aDrawMode == DrawMode::GLYPH_PATH) {
+            cairo_glyph_path(aCR, mGlyphBuffer, mNumGlyphs);
+        } else {
+            if ((int(aDrawMode) & (int(DrawMode::GLYPH_STROKE) | int(DrawMode::GLYPH_STROKE_UNDERNEATH))) ==
+                                  (int(DrawMode::GLYPH_STROKE) | int(DrawMode::GLYPH_STROKE_UNDERNEATH))) {
+                FlushStroke(aCR, aContextPaint, aGlobalMatrix);
+            }
+            if (int(aDrawMode) & int(DrawMode::GLYPH_FILL)) {
+                PROFILER_LABEL("GlyphBuffer", "cairo_show_glyphs");
+                nsRefPtr<gfxPattern> pattern;
+                if (aContextPaint &&
+                    !!(pattern = aContextPaint->GetFillPattern(aGlobalMatrix))) {
+                    cairo_save(aCR);
+                    cairo_set_source(aCR, pattern->CairoPattern());
+                }
+
+                cairo_show_glyphs(aCR, mGlyphBuffer, mNumGlyphs);
+
+                if (pattern) {
+                    cairo_restore(aCR);
+                }
+            }
+            if ((int(aDrawMode) & (int(DrawMode::GLYPH_STROKE) | int(DrawMode::GLYPH_STROKE_UNDERNEATH))) ==
+                                  int(DrawMode::GLYPH_STROKE)) {
+                FlushStroke(aCR, aContextPaint, aGlobalMatrix);
+            }
+        }
+
+        mNumGlyphs = 0;
+    }
+
+private:
+    void FlushStroke(cairo_t *aCR, gfxTextContextPaint *aContextPaint,
+                     const gfxMatrix& aGlobalMatrix) {
+        nsRefPtr<gfxPattern> pattern;
+        if (aContextPaint &&
+            !!(pattern = aContextPaint->GetStrokePattern(aGlobalMatrix))) {
+            cairo_save(aCR);
+            cairo_set_source(aCR, pattern->CairoPattern());
+        }
+
+        cairo_new_path(aCR);
+        cairo_glyph_path(aCR, mGlyphBuffer, mNumGlyphs);
+        cairo_stroke(aCR);
+
+        if (pattern) {
+            cairo_restore(aCR);
+        }
+    }
+
+#undef GLYPH_BUFFER_SIZE
+};
+
+static AntialiasMode Get2DAAMode(gfxFont::AntialiasOption aAAOption) {
+  switch (aAAOption) {
+  case gfxFont::kAntialiasSubpixel:
+    return AntialiasMode::SUBPIXEL;
+  case gfxFont::kAntialiasGrayscale:
+    return AntialiasMode::GRAY;
+  case gfxFont::kAntialiasNone:
+    return AntialiasMode::NONE;
+  default:
+    return AntialiasMode::DEFAULT;
+  }
+}
+
+struct GlyphBufferAzure {
+#define GLYPH_BUFFER_SIZE (2048/sizeof(Glyph))
+    Glyph mGlyphBuffer[GLYPH_BUFFER_SIZE];
+    unsigned int mNumGlyphs;
+
+    GlyphBufferAzure()
+        : mNumGlyphs(0) { }
+
+    Glyph *AppendGlyph() {
+        return &mGlyphBuffer[mNumGlyphs++];
+    }
+
+    void Flush(DrawTarget *aDT, gfxTextContextPaint *aContextPaint, ScaledFont *aFont,
+               DrawMode aDrawMode, bool aReverse, const GlyphRenderingOptions *aOptions,
+               gfxContext *aThebesContext, const Matrix *aInvFontMatrix, const DrawOptions &aDrawOptions,
+               bool aFinish = false)
+    {
+        // Ensure there's enough room for a glyph to be added to the buffer
+        if ((!aFinish && mNumGlyphs < GLYPH_BUFFER_SIZE) || !mNumGlyphs) {
+            return;
+        }
+
+        if (aReverse) {
+            Glyph *begin = &mGlyphBuffer[0];
+            Glyph *end = &mGlyphBuffer[mNumGlyphs];
+            std::reverse(begin, end);
+        }
+        
+        gfx::GlyphBuffer buf;
+        buf.mGlyphs = mGlyphBuffer;
+        buf.mNumGlyphs = mNumGlyphs;
+
+        gfxContext::AzureState state = aThebesContext->CurrentState();
+        if ((int(aDrawMode) & (int(DrawMode::GLYPH_STROKE) | int(DrawMode::GLYPH_STROKE_UNDERNEATH))) ==
+                              (int(DrawMode::GLYPH_STROKE) | int(DrawMode::GLYPH_STROKE_UNDERNEATH))) {
+            FlushStroke(aDT, aContextPaint, aFont, aThebesContext, buf, state);
+        }
+        if (int(aDrawMode) & int(DrawMode::GLYPH_FILL)) {
+            if (state.pattern || aContextPaint) {
+                Pattern *pat;
+
+                nsRefPtr<gfxPattern> fillPattern;
+                if (!aContextPaint ||
+                    !(fillPattern = aContextPaint->GetFillPattern(aThebesContext->CurrentMatrix()))) {
+                    if (state.pattern) {
+                        pat = state.pattern->GetPattern(aDT, state.patternTransformChanged ? &state.patternTransform : nullptr);
+                    } else {
+                        pat = nullptr;
+                    }
+                } else {
+                    pat = fillPattern->GetPattern(aDT);
+                }
+
+                if (pat) {
+                    Matrix saved;
+                    Matrix *mat = nullptr;
+                    if (aInvFontMatrix) {
+                        // The brush matrix needs to be multiplied with the inverted matrix
+                        // as well, to move the brush into the space of the glyphs. Before
+                        // the render target transformation
+
+                        // This relies on the returned Pattern not to be reused by
+                        // others, but regenerated on GetPattern calls. This is true!
+                        if (pat->GetType() == PatternType::LINEAR_GRADIENT) {
+                            mat = &static_cast<LinearGradientPattern*>(pat)->mMatrix;
+                        } else if (pat->GetType() == PatternType::RADIAL_GRADIENT) {
+                            mat = &static_cast<RadialGradientPattern*>(pat)->mMatrix;
+                        } else if (pat->GetType() == PatternType::SURFACE) {
+                            mat = &static_cast<SurfacePattern*>(pat)->mMatrix;
+                        }
+
+                        if (mat) {
+                            saved = *mat;
+                            *mat = (*mat) * (*aInvFontMatrix);
+                        }
+                    }
+
+                    aDT->FillGlyphs(aFont, buf, *pat,
+                                    aDrawOptions, aOptions);
+
+                    if (mat) {
+                        *mat = saved;
+                    }
+                }
+            } else if (state.sourceSurface) {
+                aDT->FillGlyphs(aFont, buf, SurfacePattern(state.sourceSurface,
+                                                           ExtendMode::CLAMP,
+                                                           state.surfTransform),
+                                aDrawOptions, aOptions);
+            } else {
+                aDT->FillGlyphs(aFont, buf, ColorPattern(state.color),
+                                aDrawOptions, aOptions);
+            }
+        }
+        if (int(aDrawMode) & int(DrawMode::GLYPH_PATH)) {
+            aThebesContext->EnsurePathBuilder();
+			Matrix mat = aDT->GetTransform();
+            aFont->CopyGlyphsToBuilder(buf, aThebesContext->mPathBuilder, aDT->GetType(), &mat);
+        }
+        if ((int(aDrawMode) & (int(DrawMode::GLYPH_STROKE) | int(DrawMode::GLYPH_STROKE_UNDERNEATH))) ==
+                              int(DrawMode::GLYPH_STROKE)) {
+            FlushStroke(aDT, aContextPaint, aFont, aThebesContext, buf, state);
+        }
+
+        mNumGlyphs = 0;
+    }
+
+private:
+    void FlushStroke(DrawTarget *aDT, gfxTextContextPaint *aContextPaint,
+                     ScaledFont *aFont, gfxContext *aThebesContext,
+                     gfx::GlyphBuffer& aBuf, gfxContext::AzureState& aState)
+    {
+        RefPtr<Path> path = aFont->GetPathForGlyphs(aBuf, aDT);
+        if (aContextPaint) {
+            nsRefPtr<gfxPattern> strokePattern =
+              aContextPaint->GetStrokePattern(aThebesContext->CurrentMatrix());
+            if (strokePattern) {
+                aDT->Stroke(path, *strokePattern->GetPattern(aDT), aState.strokeOptions);
+            }
+        }
+    }
+
+#undef GLYPH_BUFFER_SIZE
+};
+
+// Bug 674909. When synthetic bolding text by drawing twice, need to
+// render using a pixel offset in device pixels, otherwise text
+// doesn't appear bolded, it appears as if a bad text shadow exists
+// when a non-identity transform exists.  Use an offset factor so that
+// the second draw occurs at a constant offset in device pixels.
+
+double
+gfxFont::CalcXScale(gfxContext *aContext)
+{
+    // determine magnitude of a 1px x offset in device space
+    gfxSize t = aContext->UserToDevice(gfxSize(1.0, 0.0));
+    if (t.width == 1.0 && t.height == 0.0) {
+        // short-circuit the most common case to avoid sqrt() and division
+        return 1.0;
+    }
+
+    double m = sqrt(t.width * t.width + t.height * t.height);
+
+    NS_ASSERTION(m != 0.0, "degenerate transform while synthetic bolding");
+    if (m == 0.0) {
+        return 0.0; // effectively disables offset
+    }
+
+    // scale factor so that offsets are 1px in device pixels
+    return 1.0 / m;
+}
+
+static DrawMode
+ForcePaintingDrawMode(DrawMode aDrawMode)
+{
+    return aDrawMode == DrawMode::GLYPH_PATH ?
+        DrawMode(int(DrawMode::GLYPH_FILL) | int(DrawMode::GLYPH_STROKE)) :
+        aDrawMode;
+}
+
+void
+gfxFont::Draw(gfxTextRun *aTextRun, uint32_t aStart, uint32_t aEnd,
+              gfxContext *aContext, DrawMode aDrawMode, gfxPoint *aPt,
+              Spacing *aSpacing, gfxTextContextPaint *aContextPaint,
+              gfxTextRunDrawCallbacks *aCallbacks)
+{
+    NS_ASSERTION(aDrawMode == DrawMode::GLYPH_PATH || !(int(aDrawMode) & int(DrawMode::GLYPH_PATH)),
+                 "GLYPH_PATH cannot be used with GLYPH_FILL, GLYPH_STROKE or GLYPH_STROKE_UNDERNEATH");
+
+    if (aStart >= aEnd)
+        return;
+
+    const gfxTextRun::CompressedGlyph *charGlyphs = aTextRun->GetCharacterGlyphs();
+    const int32_t appUnitsPerDevUnit = aTextRun->GetAppUnitsPerDevUnit();
+    const double devUnitsPerAppUnit = 1.0/double(appUnitsPerDevUnit);
+    bool isRTL = aTextRun->IsRightToLeft();
+    double direction = aTextRun->GetDirection();
+    gfxMatrix globalMatrix = aContext->CurrentMatrix();
+
+    bool haveSVGGlyphs = GetFontEntry()->TryGetSVGData(this);
+    nsAutoPtr<gfxTextContextPaint> contextPaint;
+    if (haveSVGGlyphs && !aContextPaint) {
+        // If no pattern is specified for fill, use the current pattern
+        NS_ASSERTION((int(aDrawMode) & int(DrawMode::GLYPH_STROKE)) == 0, "no pattern supplied for stroking text");
+        nsRefPtr<gfxPattern> fillPattern = aContext->GetPattern();
+        contextPaint = new SimpleTextContextPaint(fillPattern, nullptr,
+                                                 aContext->CurrentMatrix());
+        aContextPaint = contextPaint;
+    }
+
+    // synthetic-bold strikes are each offset one device pixel in run direction
+    // (these values are only needed if IsSyntheticBold() is true)
+    double synBoldOnePixelOffset = 0;
+    int32_t strikes = 1;
+    if (IsSyntheticBold()) {
+        double xscale = CalcXScale(aContext);
+        synBoldOnePixelOffset = direction * xscale;
+        if (xscale != 0.0) {
+            // use as many strikes as needed for the the increased advance
+            strikes = NS_lroundf(GetSyntheticBoldOffset() / xscale);
+        }
+    }
+
+    uint32_t i;
+    // Current position in appunits
+    double x = aPt->x;
+    double y = aPt->y;
+
+    cairo_t *cr = aContext->GetCairo();
+    RefPtr<DrawTarget> dt = aContext->GetDrawTarget();
+
+    bool paintSVGGlyphs = !aCallbacks || aCallbacks->mShouldPaintSVGGlyphs;
+    bool emittedGlyphs = false;
+
+    if (aContext->IsCairo()) {
+      bool success = SetupCairoFont(aContext);
+      if (MOZ_UNLIKELY(!success))
+          return;
+
+      ::GlyphBuffer glyphs;
+      cairo_glyph_t *glyph;
+
+      if (aSpacing) {
+          x += direction*aSpacing[0].mBefore;
+      }
+      for (i = aStart; i < aEnd; ++i) {
+          const gfxTextRun::CompressedGlyph *glyphData = &charGlyphs[i];
+          if (glyphData->IsSimpleGlyph()) {
+              double advance = glyphData->GetSimpleAdvance();
+              double glyphX;
+              if (isRTL) {
+                  x -= advance;
+                  glyphX = x;
+              } else {
+                  glyphX = x;
+                  x += advance;
+              }
+
+              if (haveSVGGlyphs) {
+                  if (!paintSVGGlyphs) {
+                      continue;
+                  }
+                  gfxPoint point(ToDeviceUnits(glyphX, devUnitsPerAppUnit),
+                                 ToDeviceUnits(y, devUnitsPerAppUnit));
+                  DrawMode mode = ForcePaintingDrawMode(aDrawMode);
+                  if (RenderSVGGlyph(aContext, point, mode,
+                                     glyphData->GetSimpleGlyph(), aContextPaint,
+                                     aCallbacks, emittedGlyphs)) {
+                      continue;
+                  }
+              }
+
+              // Perhaps we should put a scale in the cairo context instead of
+              // doing this scaling here...
+              // Multiplying by the reciprocal may introduce tiny error here,
+              // but we assume cairo is going to round coordinates at some stage
+              // and this is faster
+              glyph = glyphs.AppendGlyph();
+              glyph->index = glyphData->GetSimpleGlyph();
+              glyph->x = ToDeviceUnits(glyphX, devUnitsPerAppUnit);
+              glyph->y = ToDeviceUnits(y, devUnitsPerAppUnit);
+              glyphs.Flush(cr, aDrawMode, isRTL, aContextPaint, globalMatrix);
+            
+              // synthetic bolding by multi-striking with 1-pixel offsets
+              // at least once, more if there's room (large font sizes)
+              if (IsSyntheticBold()) {
+                  double strikeOffset = synBoldOnePixelOffset;
+                  int32_t strikeCount = strikes;
+                  do {
+                      cairo_glyph_t *doubleglyph;
+                      doubleglyph = glyphs.AppendGlyph();
+                      doubleglyph->index = glyph->index;
+                      doubleglyph->x =
+                          ToDeviceUnits(glyphX + strikeOffset * appUnitsPerDevUnit,
+                                        devUnitsPerAppUnit);
+                      doubleglyph->y = glyph->y;
+                      strikeOffset += synBoldOnePixelOffset;
+                      glyphs.Flush(cr, aDrawMode, isRTL, aContextPaint, globalMatrix);
+                  } while (--strikeCount > 0);
+              }
+              emittedGlyphs = true;
+          } else {
+              uint32_t glyphCount = glyphData->GetGlyphCount();
+              if (glyphCount > 0) {
+                  const gfxTextRun::DetailedGlyph *details =
+                      aTextRun->GetDetailedGlyphs(i);
+                  NS_ASSERTION(details, "detailedGlyph should not be missing!");
+                  double advance;
+                  for (uint32_t j = 0; j < glyphCount; ++j, ++details, x += direction * advance) {
+                      advance = details->mAdvance;
+                      if (glyphData->IsMissing()) {
+                          // default ignorable characters will have zero advance width.
+                          // we don't have to draw the hexbox for them
+                          if (aDrawMode != DrawMode::GLYPH_PATH && advance > 0) {
+                              double glyphX = x;
+                              if (isRTL) {
+                                  glyphX -= advance;
+                              }
+                              gfxPoint pt(ToDeviceUnits(glyphX, devUnitsPerAppUnit),
+                                          ToDeviceUnits(y, devUnitsPerAppUnit));
+                              gfxFloat advanceDevUnits = ToDeviceUnits(advance, devUnitsPerAppUnit);
+                              gfxFloat height = GetMetrics().maxAscent;
+                              gfxRect glyphRect(pt.x, pt.y - height, advanceDevUnits, height);
+                              gfxFontMissingGlyphs::DrawMissingGlyph(aContext,
+                                                                     glyphRect,
+                                                                     details->mGlyphID,
+                                                                     appUnitsPerDevUnit);
+                          }
+                      } else {
+                          double glyphX = x + details->mXOffset;
+                          if (isRTL) {
+                              glyphX -= advance;
+                          }
+
+                          gfxPoint point(ToDeviceUnits(glyphX, devUnitsPerAppUnit),
+                                         ToDeviceUnits(y, devUnitsPerAppUnit));
+
+                          if (haveSVGGlyphs) {
+                              if (!paintSVGGlyphs) {
+                                  continue;
+                              }
+                              DrawMode mode = ForcePaintingDrawMode(aDrawMode);
+                              if (RenderSVGGlyph(aContext, point, mode,
+                                                  details->mGlyphID,
+                                                  aContextPaint, aCallbacks,
+                                                  emittedGlyphs)) {
+                                  continue;
+                              }
+                          }
+
+                          glyph = glyphs.AppendGlyph();
+                          glyph->index = details->mGlyphID;
+                          glyph->x = ToDeviceUnits(glyphX, devUnitsPerAppUnit);
+                          glyph->y = ToDeviceUnits(y + details->mYOffset, devUnitsPerAppUnit);
+                          glyphs.Flush(cr, aDrawMode, isRTL, aContextPaint, globalMatrix);
+
+                          if (IsSyntheticBold()) {
+                              double strikeOffset = synBoldOnePixelOffset;
+                              int32_t strikeCount = strikes;
+                              do {
+                                  cairo_glyph_t *doubleglyph;
+                                  doubleglyph = glyphs.AppendGlyph();
+                                  doubleglyph->index = glyph->index;
+                                  doubleglyph->x =
+                                      ToDeviceUnits(glyphX + strikeOffset *
+                                              appUnitsPerDevUnit,
+                                              devUnitsPerAppUnit);
+                                  doubleglyph->y = glyph->y;
+                                  strikeOffset += synBoldOnePixelOffset;
+                                  glyphs.Flush(cr, aDrawMode, isRTL, aContextPaint, globalMatrix);
+                              } while (--strikeCount > 0);
+                          }
+                          emittedGlyphs = true;
+                      }
+                  }
+              }
+          }
+
+          if (aSpacing) {
+              double space = aSpacing[i - aStart].mAfter;
+              if (i + 1 < aEnd) {
+                  space += aSpacing[i + 1 - aStart].mBefore;
+              }
+              x += direction*space;
+          }
+      }
+
+      if (gfxFontTestStore::CurrentStore()) {
+          /* This assumes that the tests won't have anything that results
+           * in more than GLYPH_BUFFER_SIZE glyphs.  Do this before we
+           * flush, since that'll blow away the num_glyphs.
+           */
+          gfxFontTestStore::CurrentStore()->AddItem(GetName(),
+                                                    glyphs.mGlyphBuffer,
+                                                    glyphs.mNumGlyphs);
+      }
+
+      // draw any remaining glyphs
+      glyphs.Flush(cr, aDrawMode, isRTL, aContextPaint, globalMatrix, true);
+      if (aCallbacks && emittedGlyphs) {
+          aCallbacks->NotifyGlyphPathEmitted();
+      }
+
+    } else {
+      RefPtr<ScaledFont> scaledFont = GetScaledFont(dt);
+
+      if (!scaledFont) {
+        return;
+      }
+
+      bool oldSubpixelAA = dt->GetPermitSubpixelAA();
+
+      if (!AllowSubpixelAA()) {
+          dt->SetPermitSubpixelAA(false);
+      }
+
+      GlyphBufferAzure glyphs;
+      Glyph *glyph;
+
+      Matrix mat, matInv;
+      Matrix oldMat = dt->GetTransform();
+
+      // This is nullptr when we have inverse-transformed glyphs and we need
+      // to transform the Brush inside flush.
+      Matrix *passedInvMatrix = nullptr;
+
+      RefPtr<GlyphRenderingOptions> renderingOptions =
+        GetGlyphRenderingOptions();
+
+      DrawOptions drawOptions;
+      drawOptions.mAntialiasMode = Get2DAAMode(mAntialiasOption);
+
+      // The cairo DrawTarget backend uses the cairo_scaled_font directly
+      // and so has the font skew matrix applied already.
+      if (mScaledFont &&
+          dt->GetType() != BackendType::CAIRO) {
+        cairo_matrix_t matrix;
+        cairo_scaled_font_get_font_matrix(mScaledFont, &matrix);
+        if (matrix.xy != 0) {
+          // If this matrix applies a skew, which can happen when drawing
+          // oblique fonts, we will set the DrawTarget matrix to apply the
+          // skew. We'll need to move the glyphs by the inverse of the skew to
+          // get the glyphs positioned correctly in the new device space
+          // though, since the font matrix should only be applied to drawing
+          // the glyphs, and not to their position.
+          mat = ToMatrix(*reinterpret_cast<gfxMatrix*>(&matrix));
+
+          mat._11 = mat._22 = 1.0;
+          float adjustedSize = mAdjustedSize > 0 ? mAdjustedSize : GetStyle()->size;
+          mat._21 /= adjustedSize;
+
+          dt->SetTransform(mat * oldMat);
+
+          matInv = mat;
+          matInv.Invert();
+
+          passedInvMatrix = &matInv;
+        }
+      }
+
+      if (aSpacing) {
+          x += direction*aSpacing[0].mBefore;
+      }
+      for (i = aStart; i < aEnd; ++i) {
+          const gfxTextRun::CompressedGlyph *glyphData = &charGlyphs[i];
+          if (glyphData->IsSimpleGlyph()) {
+              double advance = glyphData->GetSimpleAdvance();
+              double glyphX;
+              if (isRTL) {
+                  x -= advance;
+                  glyphX = x;
+              } else {
+                  glyphX = x;
+                  x += advance;
+              }
+
+              if (haveSVGGlyphs) {
+                  if (!paintSVGGlyphs) {
+                      continue;
+                  }
+                  gfxPoint point(ToDeviceUnits(glyphX, devUnitsPerAppUnit),
+                                 ToDeviceUnits(y, devUnitsPerAppUnit));
+                  DrawMode mode = ForcePaintingDrawMode(aDrawMode);
+                  if (RenderSVGGlyph(aContext, point, mode,
+                                     glyphData->GetSimpleGlyph(), aContextPaint,
+                                     aCallbacks, emittedGlyphs)) {
+                      continue;
+                  }
+              }
+
+              // Perhaps we should put a scale in the cairo context instead of
+              // doing this scaling here...
+              // Multiplying by the reciprocal may introduce tiny error here,
+              // but we assume cairo is going to round coordinates at some stage
+              // and this is faster
+              glyph = glyphs.AppendGlyph();
+              glyph->mIndex = glyphData->GetSimpleGlyph();
+              glyph->mPosition.x = ToDeviceUnits(glyphX, devUnitsPerAppUnit);
+              glyph->mPosition.y = ToDeviceUnits(y, devUnitsPerAppUnit);
+              glyph->mPosition = matInv * glyph->mPosition;
+              glyphs.Flush(dt, aContextPaint, scaledFont,
+                           aDrawMode, isRTL, renderingOptions,
+                           aContext, passedInvMatrix,
+                           drawOptions);
+
+              // synthetic bolding by multi-striking with 1-pixel offsets
+              // at least once, more if there's room (large font sizes)
+              if (IsSyntheticBold()) {
+                  double strikeOffset = synBoldOnePixelOffset;
+                  int32_t strikeCount = strikes;
+                  do {
+                      Glyph *doubleglyph;
+                      doubleglyph = glyphs.AppendGlyph();
+                      doubleglyph->mIndex = glyph->mIndex;
+                      doubleglyph->mPosition.x =
+                          ToDeviceUnits(glyphX + strikeOffset * appUnitsPerDevUnit,
+                                        devUnitsPerAppUnit);
+                      doubleglyph->mPosition.y = glyph->mPosition.y;
+                      doubleglyph->mPosition = matInv * doubleglyph->mPosition;
+                      strikeOffset += synBoldOnePixelOffset;
+                      glyphs.Flush(dt, aContextPaint, scaledFont,
+                                   aDrawMode, isRTL, renderingOptions,
+                                   aContext, passedInvMatrix,
+                                   drawOptions);
+                  } while (--strikeCount > 0);
+              }
+              emittedGlyphs = true;
+          } else {
+              uint32_t glyphCount = glyphData->GetGlyphCount();
+              if (glyphCount > 0) {
+                  const gfxTextRun::DetailedGlyph *details =
+                      aTextRun->GetDetailedGlyphs(i);
+                  NS_ASSERTION(details, "detailedGlyph should not be missing!");
+                  double advance;
+                  for (uint32_t j = 0; j < glyphCount; ++j, ++details, x += direction * advance) {
+                      advance = details->mAdvance;
+                      if (glyphData->IsMissing()) {
+                          // default ignorable characters will have zero advance width.
+                          // we don't have to draw the hexbox for them
+                          if (aDrawMode != DrawMode::GLYPH_PATH && advance > 0) {
+                              double glyphX = x;
+                              if (isRTL) {
+                                  glyphX -= advance;
+                              }
+                              gfxPoint pt(ToDeviceUnits(glyphX, devUnitsPerAppUnit),
+                                          ToDeviceUnits(y, devUnitsPerAppUnit));
+                              gfxFloat advanceDevUnits = ToDeviceUnits(advance, devUnitsPerAppUnit);
+                              gfxFloat height = GetMetrics().maxAscent;
+                              gfxRect glyphRect(pt.x, pt.y - height, advanceDevUnits, height);
+                              gfxFontMissingGlyphs::DrawMissingGlyph(aContext,
+                                                                     glyphRect,
+                                                                     details->mGlyphID,
+                                                                     appUnitsPerDevUnit);
+                          }
+                      } else {
+                          double glyphX = x + details->mXOffset;
+                          if (isRTL) {
+                              glyphX -= advance;
+                          }
+
+                          gfxPoint point(ToDeviceUnits(glyphX, devUnitsPerAppUnit),
+                                         ToDeviceUnits(y, devUnitsPerAppUnit));
+
+                          if (haveSVGGlyphs) {
+                              if (!paintSVGGlyphs) {
+                                  continue;
+                              }
+                              DrawMode mode = ForcePaintingDrawMode(aDrawMode);
+                              if (RenderSVGGlyph(aContext, point, mode,
+                                                 details->mGlyphID,
+                                                 aContextPaint, aCallbacks,
+                                                 emittedGlyphs)) {
+                                  continue;
+                              }
+                          }
+
+                          glyph = glyphs.AppendGlyph();
+                          glyph->mIndex = details->mGlyphID;
+                          glyph->mPosition.x = ToDeviceUnits(glyphX, devUnitsPerAppUnit);
+                          glyph->mPosition.y = ToDeviceUnits(y + details->mYOffset, devUnitsPerAppUnit);
+                          glyph->mPosition = matInv * glyph->mPosition;
+                          glyphs.Flush(dt, aContextPaint, scaledFont, aDrawMode,
+                                       isRTL, renderingOptions, aContext, passedInvMatrix,
+                                       drawOptions);
+
+                          if (IsSyntheticBold()) {
+                              double strikeOffset = synBoldOnePixelOffset;
+                              int32_t strikeCount = strikes;
+                              do {
+                                  Glyph *doubleglyph;
+                                  doubleglyph = glyphs.AppendGlyph();
+                                  doubleglyph->mIndex = glyph->mIndex;
+                                  doubleglyph->mPosition.x =
+                                      ToDeviceUnits(glyphX + strikeOffset *
+                                                    appUnitsPerDevUnit,
+                                                    devUnitsPerAppUnit);
+                                  doubleglyph->mPosition.y = glyph->mPosition.y;
+                                  strikeOffset += synBoldOnePixelOffset;
+                                  doubleglyph->mPosition = matInv * doubleglyph->mPosition;
+                                  glyphs.Flush(dt, aContextPaint, scaledFont,
+                                               aDrawMode, isRTL, renderingOptions,
+                                               aContext, passedInvMatrix, drawOptions);
+                              } while (--strikeCount > 0);
+                          }
+                          emittedGlyphs = true;
+                      }
+                  }
+              }
+          }
+
+          if (aSpacing) {
+              double space = aSpacing[i - aStart].mAfter;
+              if (i + 1 < aEnd) {
+                  space += aSpacing[i + 1 - aStart].mBefore;
+              }
+              x += direction*space;
+          }
+      }
+
+      glyphs.Flush(dt, aContextPaint, scaledFont, aDrawMode, isRTL,
+                   renderingOptions, aContext, passedInvMatrix,
+                   drawOptions, true);
+      if (aCallbacks && emittedGlyphs) {
+          aCallbacks->NotifyGlyphPathEmitted();
+      }
+
+      dt->SetTransform(oldMat);
+
+      dt->SetPermitSubpixelAA(oldSubpixelAA);
+    }
+
+    *aPt = gfxPoint(x, y);
+}
+
+bool
+gfxFont::RenderSVGGlyph(gfxContext *aContext, gfxPoint aPoint, DrawMode aDrawMode,
+                        uint32_t aGlyphId, gfxTextContextPaint *aContextPaint)
+{
+    if (!GetFontEntry()->HasSVGGlyph(aGlyphId)) {
+        return false;
+    }
+
+    const gfxFloat devUnitsPerSVGUnit =
+        GetAdjustedSize() / GetFontEntry()->UnitsPerEm();
+    gfxContextMatrixAutoSaveRestore matrixRestore(aContext);
+
+    aContext->Translate(gfxPoint(aPoint.x, aPoint.y));
+    aContext->Scale(devUnitsPerSVGUnit, devUnitsPerSVGUnit);
+
+    aContextPaint->InitStrokeGeometry(aContext, devUnitsPerSVGUnit);
+
+    return GetFontEntry()->RenderSVGGlyph(aContext, aGlyphId, int(aDrawMode),
+                                          aContextPaint);
+}
+
+bool
+gfxFont::RenderSVGGlyph(gfxContext *aContext, gfxPoint aPoint, DrawMode aDrawMode,
+                        uint32_t aGlyphId, gfxTextContextPaint *aContextPaint,
+                        gfxTextRunDrawCallbacks *aCallbacks,
+                        bool& aEmittedGlyphs)
+{
+    if (aCallbacks) {
+        if (aEmittedGlyphs) {
+            aCallbacks->NotifyGlyphPathEmitted();
+            aEmittedGlyphs = false;
+        }
+        aCallbacks->NotifyBeforeSVGGlyphPainted();
+    }
+    bool rendered = RenderSVGGlyph(aContext, aPoint, aDrawMode, aGlyphId,
+                                   aContextPaint);
+    if (aCallbacks) {
+        aCallbacks->NotifyAfterSVGGlyphPainted();
+    }
+    return rendered;
+}
+
+static void
+UnionRange(gfxFloat aX, gfxFloat* aDestMin, gfxFloat* aDestMax)
+{
+    *aDestMin = std::min(*aDestMin, aX);
+    *aDestMax = std::max(*aDestMax, aX);
+}
+
+// We get precise glyph extents if the textrun creator requested them, or
+// if the font is a user font --- in which case the author may be relying
+// on overflowing glyphs.
+static bool
+NeedsGlyphExtents(gfxFont *aFont, gfxTextRun *aTextRun)
+{
+    return (aTextRun->GetFlags() & gfxTextRunFactory::TEXT_NEED_BOUNDING_BOX) ||
+        aFont->GetFontEntry()->IsUserFont();
+}
+
+static bool
+NeedsGlyphExtents(gfxTextRun *aTextRun)
+{
+    if (aTextRun->GetFlags() & gfxTextRunFactory::TEXT_NEED_BOUNDING_BOX)
+        return true;
+    uint32_t numRuns;
+    const gfxTextRun::GlyphRun *glyphRuns = aTextRun->GetGlyphRuns(&numRuns);
+    for (uint32_t i = 0; i < numRuns; ++i) {
+        if (glyphRuns[i].mFont->GetFontEntry()->IsUserFont())
+            return true;
+    }
+    return false;
+}
+
+gfxFont::RunMetrics
+gfxFont::Measure(gfxTextRun *aTextRun,
+                 uint32_t aStart, uint32_t aEnd,
+                 BoundingBoxType aBoundingBoxType,
+                 gfxContext *aRefContext,
+                 Spacing *aSpacing)
+{
+    // If aBoundingBoxType is TIGHT_HINTED_OUTLINE_EXTENTS
+    // and the underlying cairo font may be antialiased,
+    // we need to create a copy in order to avoid getting cached extents.
+    // This is only used by MathML layout at present.
+    if (aBoundingBoxType == TIGHT_HINTED_OUTLINE_EXTENTS &&
+        mAntialiasOption != kAntialiasNone) {
+        if (!mNonAAFont) {
+            mNonAAFont = CopyWithAntialiasOption(kAntialiasNone);
+        }
+        // if font subclass doesn't implement CopyWithAntialiasOption(),
+        // it will return null and we'll proceed to use the existing font
+        if (mNonAAFont) {
+            return mNonAAFont->Measure(aTextRun, aStart, aEnd,
+                                       TIGHT_HINTED_OUTLINE_EXTENTS,
+                                       aRefContext, aSpacing);
+        }
+    }
+
+    const int32_t appUnitsPerDevUnit = aTextRun->GetAppUnitsPerDevUnit();
+    // Current position in appunits
+    const gfxFont::Metrics& fontMetrics = GetMetrics();
+
+    RunMetrics metrics;
+    metrics.mAscent = fontMetrics.maxAscent*appUnitsPerDevUnit;
+    metrics.mDescent = fontMetrics.maxDescent*appUnitsPerDevUnit;
+    if (aStart == aEnd) {
+        // exit now before we look at aSpacing[0], which is undefined
+        metrics.mBoundingBox = gfxRect(0, -metrics.mAscent, 0, metrics.mAscent + metrics.mDescent);
+        return metrics;
+    }
+
+    gfxFloat advanceMin = 0, advanceMax = 0;
+    const gfxTextRun::CompressedGlyph *charGlyphs = aTextRun->GetCharacterGlyphs();
+    bool isRTL = aTextRun->IsRightToLeft();
+    double direction = aTextRun->GetDirection();
+    bool needsGlyphExtents = NeedsGlyphExtents(this, aTextRun);
+    gfxGlyphExtents *extents =
+        (aBoundingBoxType == LOOSE_INK_EXTENTS &&
+            !needsGlyphExtents &&
+            !aTextRun->HasDetailedGlyphs()) ? nullptr
+        : GetOrCreateGlyphExtents(aTextRun->GetAppUnitsPerDevUnit());
+    double x = 0;
+    if (aSpacing) {
+        x += direction*aSpacing[0].mBefore;
+    }
+    uint32_t i;
+    for (i = aStart; i < aEnd; ++i) {
+        const gfxTextRun::CompressedGlyph *glyphData = &charGlyphs[i];
+        if (glyphData->IsSimpleGlyph()) {
+            double advance = glyphData->GetSimpleAdvance();
+            // Only get the real glyph horizontal extent if we were asked
+            // for the tight bounding box or we're in quality mode
+            if ((aBoundingBoxType != LOOSE_INK_EXTENTS || needsGlyphExtents) &&
+                extents) {
+                uint32_t glyphIndex = glyphData->GetSimpleGlyph();
+                uint16_t extentsWidth = extents->GetContainedGlyphWidthAppUnits(glyphIndex);
+                if (extentsWidth != gfxGlyphExtents::INVALID_WIDTH &&
+                    aBoundingBoxType == LOOSE_INK_EXTENTS) {
+                    UnionRange(x, &advanceMin, &advanceMax);
+                    UnionRange(x + direction*extentsWidth, &advanceMin, &advanceMax);
+                } else {
+                    gfxRect glyphRect;
+                    if (!extents->GetTightGlyphExtentsAppUnits(this,
+                            aRefContext, glyphIndex, &glyphRect)) {
+                        glyphRect = gfxRect(0, metrics.mBoundingBox.Y(),
+                            advance, metrics.mBoundingBox.Height());
+                    }
+                    if (isRTL) {
+                        glyphRect -= gfxPoint(advance, 0);
+                    }
+                    glyphRect += gfxPoint(x, 0);
+                    metrics.mBoundingBox = metrics.mBoundingBox.Union(glyphRect);
+                }
+            }
+            x += direction*advance;
+        } else {
+            uint32_t glyphCount = glyphData->GetGlyphCount();
+            if (glyphCount > 0) {
+                const gfxTextRun::DetailedGlyph *details =
+                    aTextRun->GetDetailedGlyphs(i);
+                NS_ASSERTION(details != nullptr,
+                             "detaiedGlyph record should not be missing!");
+                uint32_t j;
+                for (j = 0; j < glyphCount; ++j, ++details) {
+                    uint32_t glyphIndex = details->mGlyphID;
+                    gfxPoint glyphPt(x + details->mXOffset, details->mYOffset);
+                    double advance = details->mAdvance;
+                    gfxRect glyphRect;
+                    if (glyphData->IsMissing() || !extents ||
+                        !extents->GetTightGlyphExtentsAppUnits(this,
+                                aRefContext, glyphIndex, &glyphRect)) {
+                        // We might have failed to get glyph extents due to
+                        // OOM or something
+                        glyphRect = gfxRect(0, -metrics.mAscent,
+                            advance, metrics.mAscent + metrics.mDescent);
+                    }
+                    if (isRTL) {
+                        glyphRect -= gfxPoint(advance, 0);
+                    }
+                    glyphRect += gfxPoint(x, 0);
+                    metrics.mBoundingBox = metrics.mBoundingBox.Union(glyphRect);
+                    x += direction*advance;
+                }
+            }
+        }
+        // Every other glyph type is ignored
+        if (aSpacing) {
+            double space = aSpacing[i - aStart].mAfter;
+            if (i + 1 < aEnd) {
+                space += aSpacing[i + 1 - aStart].mBefore;
+            }
+            x += direction*space;
+        }
+    }
+
+    if (aBoundingBoxType == LOOSE_INK_EXTENTS) {
+        UnionRange(x, &advanceMin, &advanceMax);
+        gfxRect fontBox(advanceMin, -metrics.mAscent,
+                        advanceMax - advanceMin, metrics.mAscent + metrics.mDescent);
+        metrics.mBoundingBox = metrics.mBoundingBox.Union(fontBox);
+    }
+    if (isRTL) {
+        metrics.mBoundingBox -= gfxPoint(x, 0);
+    }
+
+    metrics.mAdvanceWidth = x*direction;
+    return metrics;
+}
+
+static PLDHashOperator
+NotifyGlyphChangeObservers(nsPtrHashKey<gfxFont::GlyphChangeObserver>* aKey,
+                           void* aClosure)
+{
+    aKey->GetKey()->NotifyGlyphsChanged();
+    return PL_DHASH_NEXT;
+}
+
+void
+gfxFont::NotifyGlyphsChanged()
+{
+    uint32_t i, count = mGlyphExtentsArray.Length();
+    for (i = 0; i < count; ++i) {
+        // Flush cached extents array
+        mGlyphExtentsArray[i]->NotifyGlyphsChanged();
+    }
+
+    if (mGlyphChangeObservers) {
+        mGlyphChangeObservers->EnumerateEntries(NotifyGlyphChangeObservers, nullptr);
+    }
+}
+
+static bool
+IsBoundarySpace(char16_t aChar, char16_t aNextChar)
+{
+    return (aChar == ' ' || aChar == 0x00A0) && !IsClusterExtender(aNextChar);
+}
+
+static inline uint32_t
+HashMix(uint32_t aHash, char16_t aCh)
+{
+    return (aHash >> 28) ^ (aHash << 4) ^ aCh;
+}
+
+#ifdef __GNUC__
+#define GFX_MAYBE_UNUSED __attribute__((unused))
+#else
+#define GFX_MAYBE_UNUSED
+#endif
+
+template<typename T>
+gfxShapedWord*
+gfxFont::GetShapedWord(gfxContext *aContext,
+                       const T    *aText,
+                       uint32_t    aLength,
+                       uint32_t    aHash,
+                       int32_t     aRunScript,
+                       int32_t     aAppUnitsPerDevUnit,
+                       uint32_t    aFlags,
+                       gfxTextPerfMetrics *aTextPerf GFX_MAYBE_UNUSED)
+{
+    // if the cache is getting too big, flush it and start over
+    uint32_t wordCacheMaxEntries =
+        gfxPlatform::GetPlatform()->WordCacheMaxEntries();
+    if (mWordCache->Count() > wordCacheMaxEntries) {
+        NS_WARNING("flushing shaped-word cache");
+        ClearCachedWords();
+    }
+
+    // if there's a cached entry for this word, just return it
+    CacheHashKey key(aText, aLength, aHash,
+                     aRunScript,
+                     aAppUnitsPerDevUnit,
+                     aFlags);
+
+    CacheHashEntry *entry = mWordCache->PutEntry(key);
+    if (!entry) {
+        NS_WARNING("failed to create word cache entry - expect missing text");
+        return nullptr;
+    }
+    gfxShapedWord *sw = entry->mShapedWord;
+
+    bool isContent = !mStyle.systemFont;
+
+    if (sw) {
+        sw->ResetAge();
+        Telemetry::Accumulate((isContent ? Telemetry::WORD_CACHE_HITS_CONTENT :
+                                   Telemetry::WORD_CACHE_HITS_CHROME),
+                              aLength);
+#ifndef RELEASE_BUILD
+        if (aTextPerf) {
+            aTextPerf->current.wordCacheHit++;
+        }
+#endif
+        return sw;
+    }
+
+    Telemetry::Accumulate((isContent ? Telemetry::WORD_CACHE_MISSES_CONTENT :
+                               Telemetry::WORD_CACHE_MISSES_CHROME),
+                          aLength);
+#ifndef RELEASE_BUILD
+    if (aTextPerf) {
+        aTextPerf->current.wordCacheMiss++;
+    }
+#endif
+
+    sw = entry->mShapedWord = gfxShapedWord::Create(aText, aLength,
+                                                    aRunScript,
+                                                    aAppUnitsPerDevUnit,
+                                                    aFlags);
+    if (!sw) {
+        NS_WARNING("failed to create gfxShapedWord - expect missing text");
+        return nullptr;
+    }
+
+    DebugOnly<bool> ok =
+        ShapeText(aContext, aText, 0, aLength, aRunScript, sw);
+
+    NS_WARN_IF_FALSE(ok, "failed to shape word - expect garbled text");
+
+    return sw;
+}
+
+bool
+gfxFont::CacheHashEntry::KeyEquals(const KeyTypePointer aKey) const
+{
+    const gfxShapedWord *sw = mShapedWord;
+    if (!sw) {
+        return false;
+    }
+    if (sw->GetLength() != aKey->mLength ||
+        sw->Flags() != aKey->mFlags ||
+        sw->GetAppUnitsPerDevUnit() != aKey->mAppUnitsPerDevUnit ||
+        sw->Script() != aKey->mScript) {
+        return false;
+    }
+    if (sw->TextIs8Bit()) {
+        if (aKey->mTextIs8Bit) {
+            return (0 == memcmp(sw->Text8Bit(), aKey->mText.mSingle,
+                                aKey->mLength * sizeof(uint8_t)));
+        }
+        // The key has 16-bit text, even though all the characters are < 256,
+        // so the TEXT_IS_8BIT flag was set and the cached ShapedWord we're
+        // comparing with will have 8-bit text.
+        const uint8_t   *s1 = sw->Text8Bit();
+        const char16_t *s2 = aKey->mText.mDouble;
+        const char16_t *s2end = s2 + aKey->mLength;
+        while (s2 < s2end) {
+            if (*s1++ != *s2++) {
+                return false;
+            }
+        }
+        return true;
+    }
+    NS_ASSERTION((aKey->mFlags & gfxTextRunFactory::TEXT_IS_8BIT) == 0 &&
+                 !aKey->mTextIs8Bit, "didn't expect 8-bit text here");
+    return (0 == memcmp(sw->TextUnicode(), aKey->mText.mDouble,
+                        aKey->mLength * sizeof(char16_t)));
+}
+
+bool
+gfxFont::ShapeText(gfxContext    *aContext,
+                   const uint8_t *aText,
+                   uint32_t       aOffset,
+                   uint32_t       aLength,
+                   int32_t        aScript,
+                   gfxShapedText *aShapedText,
+                   bool           aPreferPlatformShaping)
+{
+    nsDependentCSubstring ascii((const char*)aText, aLength);
+    nsAutoString utf16;
+    AppendASCIItoUTF16(ascii, utf16);
+    if (utf16.Length() != aLength) {
+        return false;
+    }
+    return ShapeText(aContext, utf16.BeginReading(), aOffset, aLength,
+                     aScript, aShapedText, aPreferPlatformShaping);
+}
+
+bool
+gfxFont::ShapeText(gfxContext      *aContext,
+                   const char16_t *aText,
+                   uint32_t         aOffset,
+                   uint32_t         aLength,
+                   int32_t          aScript,
+                   gfxShapedText   *aShapedText,
+                   bool             aPreferPlatformShaping)
+{
+    bool ok = false;
+
+    if (mGraphiteShaper && gfxPlatform::GetPlatform()->UseGraphiteShaping()) {
+        ok = mGraphiteShaper->ShapeText(aContext, aText, aOffset, aLength,
+                                        aScript, aShapedText);
+    }
+
+    if (!ok && mHarfBuzzShaper && !aPreferPlatformShaping) {
+        if (gfxPlatform::GetPlatform()->UseHarfBuzzForScript(aScript)) {
+            ok = mHarfBuzzShaper->ShapeText(aContext, aText, aOffset, aLength,
+                                            aScript, aShapedText);
+        }
+    }
+
+    if (!ok) {
+        if (!mPlatformShaper) {
+            CreatePlatformShaper();
+            NS_ASSERTION(mPlatformShaper, "no platform shaper available!");
+        }
+        if (mPlatformShaper) {
+            ok = mPlatformShaper->ShapeText(aContext, aText, aOffset, aLength,
+                                            aScript, aShapedText);
+        }
+    }
+
+    PostShapingFixup(aContext, aText, aOffset, aLength, aShapedText);
+
+    return ok;
+}
+
+void
+gfxFont::PostShapingFixup(gfxContext      *aContext,
+                          const char16_t *aText,
+                          uint32_t         aOffset,
+                          uint32_t         aLength,
+                          gfxShapedText   *aShapedText)
+{
+    if (IsSyntheticBold()) {
+        float synBoldOffset =
+                GetSyntheticBoldOffset() * CalcXScale(aContext);
+        aShapedText->AdjustAdvancesForSyntheticBold(synBoldOffset,
+                                                    aOffset, aLength);
+    }
+}
+
+#define MAX_SHAPING_LENGTH  32760 // slightly less than 32K, trying to avoid
+                                  // over-stressing platform shapers
+#define BACKTRACK_LIMIT     16 // backtrack this far looking for a good place
+                               // to split into fragments for separate shaping
+
+template<typename T>
+bool
+gfxFont::ShapeFragmentWithoutWordCache(gfxContext *aContext,
+                                       const T    *aText,
+                                       uint32_t    aOffset,
+                                       uint32_t    aLength,
+                                       int32_t     aScript,
+                                       gfxTextRun *aTextRun)
+{
+    aTextRun->SetupClusterBoundaries(aOffset, aText, aLength);
+
+    bool ok = true;
+
+    while (ok && aLength > 0) {
+        uint32_t fragLen = aLength;
+
+        // limit the length of text we pass to shapers in a single call
+        if (fragLen > MAX_SHAPING_LENGTH) {
+            fragLen = MAX_SHAPING_LENGTH;
+
+            // in the 8-bit case, there are no multi-char clusters,
+            // so we don't need to do this check
+            if (sizeof(T) == sizeof(char16_t)) {
+                uint32_t i;
+                for (i = 0; i < BACKTRACK_LIMIT; ++i) {
+                    if (aTextRun->IsClusterStart(aOffset + fragLen - i)) {
+                        fragLen -= i;
+                        break;
+                    }
+                }
+                if (i == BACKTRACK_LIMIT) {
+                    // if we didn't find any cluster start while backtracking,
+                    // just check that we're not in the middle of a surrogate
+                    // pair; back up by one code unit if we are.
+                    if (NS_IS_LOW_SURROGATE(aText[fragLen]) &&
+                        NS_IS_HIGH_SURROGATE(aText[fragLen - 1])) {
+                        --fragLen;
+                    }
+                }
+            }
+        }
+
+        ok = ShapeText(aContext, aText, aOffset, fragLen, aScript, aTextRun);
+
+        aText += fragLen;
+        aOffset += fragLen;
+        aLength -= fragLen;
+    }
+
+    return ok;
+}
+
+// Check if aCh is an unhandled control character that should be displayed
+// as a hexbox rather than rendered by some random font on the system.
+// We exclude \r as stray &#13;s are rather common (bug 941940).
+// Note that \n and \t don't come through here, as they have specific
+// meanings that have already been handled.
+static bool
+IsInvalidControlChar(uint32_t aCh)
+{
+    return aCh != '\r' && ((aCh & 0x7f) < 0x20 || aCh == 0x7f);
+}
+
+template<typename T>
+bool
+gfxFont::ShapeTextWithoutWordCache(gfxContext *aContext,
+                                   const T    *aText,
+                                   uint32_t    aOffset,
+                                   uint32_t    aLength,
+                                   int32_t     aScript,
+                                   gfxTextRun *aTextRun)
+{
+    uint32_t fragStart = 0;
+    bool ok = true;
+
+    for (uint32_t i = 0; i <= aLength && ok; ++i) {
+        T ch = (i < aLength) ? aText[i] : '\n';
+        bool invalid = gfxFontGroup::IsInvalidChar(ch);
+        uint32_t length = i - fragStart;
+
+        // break into separate fragments when we hit an invalid char
+        if (!invalid) {
+            continue;
+        }
+
+        if (length > 0) {
+            ok = ShapeFragmentWithoutWordCache(aContext, aText + fragStart,
+                                               aOffset + fragStart, length,
+                                               aScript, aTextRun);
+        }
+
+        if (i == aLength) {
+            break;
+        }
+
+        // fragment was terminated by an invalid char: skip it,
+        // unless it's a control char that we want to show as a hexbox,
+        // but record where TAB or NEWLINE occur
+        if (ch == '\t') {
+            aTextRun->SetIsTab(aOffset + i);
+        } else if (ch == '\n') {
+            aTextRun->SetIsNewline(aOffset + i);
+        } else if (IsInvalidControlChar(ch) &&
+            !(aTextRun->GetFlags() & gfxTextRunFactory::TEXT_HIDE_CONTROL_CHARACTERS)) {
+            aTextRun->SetMissingGlyph(aOffset + i, ch, this);
+        }
+        fragStart = i + 1;
+    }
+
+    NS_WARN_IF_FALSE(ok, "failed to shape text - expect garbled text");
+    return ok;
+}
+
+#ifndef RELEASE_BUILD
+#define TEXT_PERF_INCR(tp, m) (tp ? (tp)->current.m++ : 0)
+#else
+#define TEXT_PERF_INCR(tp, m)
+#endif
+
+inline static bool IsChar8Bit(uint8_t /*aCh*/) { return true; }
+inline static bool IsChar8Bit(char16_t aCh) { return aCh < 0x100; }
+
+inline static bool HasSpaces(const uint8_t *aString, uint32_t aLen)
+{
+    return memchr(aString, 0x20, aLen) != nullptr;
+}
+
+inline static bool HasSpaces(const char16_t *aString, uint32_t aLen)
+{
+    for (const char16_t *ch = aString; ch < aString + aLen; ch++) {
+        if (*ch == 0x20) {
+            return true;
+        }
+    }
+    return false;
+}
+
+template<typename T>
+bool
+gfxFont::SplitAndInitTextRun(gfxContext *aContext,
+                             gfxTextRun *aTextRun,
+                             const T *aString,
+                             uint32_t aRunStart,
+                             uint32_t aRunLength,
+                             int32_t aRunScript)
+{
+    if (aRunLength == 0) {
+        return true;
+    }
+
+    gfxTextPerfMetrics *tp = nullptr;
+
+#ifndef RELEASE_BUILD
+    tp = aTextRun->GetFontGroup()->GetTextPerfMetrics();
+    if (tp) {
+        if (mStyle.systemFont) {
+            tp->current.numChromeTextRuns++;
+        } else {
+            tp->current.numContentTextRuns++;
+        }
+        tp->current.numChars += aRunLength;
+        if (aRunLength > tp->current.maxTextRunLen) {
+            tp->current.maxTextRunLen = aRunLength;
+        }
+    }
+#endif
+
+    uint32_t wordCacheCharLimit =
+        gfxPlatform::GetPlatform()->WordCacheCharLimit();
+
+    // If spaces can participate in shaping (e.g. within lookups for automatic
+    // fractions), need to shape without using the word cache which segments
+    // textruns on space boundaries. Word cache can be used if the textrun
+    // is short enough to fit in the word cache and it lacks spaces.
+    if (SpaceMayParticipateInShaping(aRunScript)) {
+        if (aRunLength > wordCacheCharLimit ||
+            HasSpaces(aString + aRunStart, aRunLength)) {
+            TEXT_PERF_INCR(tp, wordCacheSpaceRules);
+            return ShapeTextWithoutWordCache(aContext, aString + aRunStart,
+                                             aRunStart, aRunLength, aRunScript,
+                                             aTextRun);
+        }
+    }
+
+    InitWordCache();
+
+    // the only flags we care about for ShapedWord construction/caching
+    uint32_t flags = aTextRun->GetFlags();
+    flags &= (gfxTextRunFactory::TEXT_IS_RTL |
+              gfxTextRunFactory::TEXT_DISABLE_OPTIONAL_LIGATURES |
+              gfxTextRunFactory::TEXT_USE_MATH_SCRIPT);
+    if (sizeof(T) == sizeof(uint8_t)) {
+        flags |= gfxTextRunFactory::TEXT_IS_8BIT;
+    }
+
+    const T *text = aString + aRunStart;
+    uint32_t wordStart = 0;
+    uint32_t hash = 0;
+    bool wordIs8Bit = true;
+    int32_t appUnitsPerDevUnit = aTextRun->GetAppUnitsPerDevUnit();
+
+    T nextCh = text[0];
+    for (uint32_t i = 0; i <= aRunLength; ++i) {
+        T ch = nextCh;
+        nextCh = (i < aRunLength - 1) ? text[i + 1] : '\n';
+        bool boundary = IsBoundarySpace(ch, nextCh);
+        bool invalid = !boundary && gfxFontGroup::IsInvalidChar(ch);
+        uint32_t length = i - wordStart;
+
+        // break into separate ShapedWords when we hit an invalid char,
+        // or a boundary space (always handled individually),
+        // or the first non-space after a space
+        if (!boundary && !invalid) {
+            if (!IsChar8Bit(ch)) {
+                wordIs8Bit = false;
+            }
+            // include this character in the hash, and move on to next
+            hash = HashMix(hash, ch);
+            continue;
+        }
+
+        // We've decided to break here (i.e. we're at the end of a "word");
+        // shape the word and add it to the textrun.
+        // For words longer than the limit, we don't use the
+        // font's word cache but just shape directly into the textrun.
+        if (length > wordCacheCharLimit) {
+            TEXT_PERF_INCR(tp, wordCacheLong);
+            bool ok = ShapeFragmentWithoutWordCache(aContext,
+                                                    text + wordStart,
+                                                    aRunStart + wordStart,
+                                                    length,
+                                                    aRunScript,
+                                                    aTextRun);
+            if (!ok) {
+                return false;
+            }
+        } else if (length > 0) {
+            uint32_t wordFlags = flags;
+            // in the 8-bit version of this method, TEXT_IS_8BIT was
+            // already set as part of |flags|, so no need for a per-word
+            // adjustment here
+            if (sizeof(T) == sizeof(char16_t)) {
+                if (wordIs8Bit) {
+                    wordFlags |= gfxTextRunFactory::TEXT_IS_8BIT;
+                }
+            }
+            gfxShapedWord *sw = GetShapedWord(aContext,
+                                              text + wordStart, length,
+                                              hash, aRunScript,
+                                              appUnitsPerDevUnit,
+                                              wordFlags, tp);
+            if (sw) {
+                aTextRun->CopyGlyphDataFrom(sw, aRunStart + wordStart);
+            } else {
+                return false; // failed, presumably out of memory?
+            }
+        }
+
+        if (boundary) {
+            // word was terminated by a space: add that to the textrun
+            if (!aTextRun->SetSpaceGlyphIfSimple(this, aContext,
+                                                 aRunStart + i, ch))
+            {
+                static const uint8_t space = ' ';
+                gfxShapedWord *sw =
+                    GetShapedWord(aContext,
+                                  &space, 1,
+                                  HashMix(0, ' '), aRunScript,
+                                  appUnitsPerDevUnit,
+                                  flags | gfxTextRunFactory::TEXT_IS_8BIT, tp);
+                if (sw) {
+                    aTextRun->CopyGlyphDataFrom(sw, aRunStart + i);
+                } else {
+                    return false;
+                }
+            }
+            hash = 0;
+            wordStart = i + 1;
+            wordIs8Bit = true;
+            continue;
+        }
+
+        if (i == aRunLength) {
+            break;
+        }
+
+        NS_ASSERTION(invalid,
+                     "how did we get here except via an invalid char?");
+
+        // word was terminated by an invalid char: skip it,
+        // unless it's a control char that we want to show as a hexbox,
+        // but record where TAB or NEWLINE occur
+        if (ch == '\t') {
+            aTextRun->SetIsTab(aRunStart + i);
+        } else if (ch == '\n') {
+            aTextRun->SetIsNewline(aRunStart + i);
+        } else if (IsInvalidControlChar(ch) &&
+            !(aTextRun->GetFlags() & gfxTextRunFactory::TEXT_HIDE_CONTROL_CHARACTERS)) {
+            aTextRun->SetMissingGlyph(aRunStart + i, ch, this);
+        }
+
+        hash = 0;
+        wordStart = i + 1;
+        wordIs8Bit = true;
+    }
+
+    return true;
+}
+
+gfxGlyphExtents *
+gfxFont::GetOrCreateGlyphExtents(int32_t aAppUnitsPerDevUnit) {
+    uint32_t i, count = mGlyphExtentsArray.Length();
+    for (i = 0; i < count; ++i) {
+        if (mGlyphExtentsArray[i]->GetAppUnitsPerDevUnit() == aAppUnitsPerDevUnit)
+            return mGlyphExtentsArray[i];
+    }
+    gfxGlyphExtents *glyphExtents = new gfxGlyphExtents(aAppUnitsPerDevUnit);
+    if (glyphExtents) {
+        mGlyphExtentsArray.AppendElement(glyphExtents);
+        // Initialize the extents of a space glyph, assuming that spaces don't
+        // render anything!
+        glyphExtents->SetContainedGlyphWidthAppUnits(GetSpaceGlyph(), 0);
+    }
+    return glyphExtents;
+}
+
+void
+gfxFont::SetupGlyphExtents(gfxContext *aContext, uint32_t aGlyphID, bool aNeedTight,
+                           gfxGlyphExtents *aExtents)
+{
+    gfxContextMatrixAutoSaveRestore matrixRestore(aContext);
+    aContext->IdentityMatrix();
+
+    gfxRect svgBounds;
+    if (mFontEntry->TryGetSVGData(this) && mFontEntry->HasSVGGlyph(aGlyphID) &&
+        mFontEntry->GetSVGGlyphExtents(aContext, aGlyphID, &svgBounds)) {
+        gfxFloat d2a = aExtents->GetAppUnitsPerDevUnit();
+        aExtents->SetTightGlyphExtents(aGlyphID,
+                                       gfxRect(svgBounds.x * d2a,
+                                               svgBounds.y * d2a,
+                                               svgBounds.width * d2a,
+                                               svgBounds.height * d2a));
+        return;
+    }
+
+    cairo_glyph_t glyph;
+    glyph.index = aGlyphID;
+    glyph.x = 0;
+    glyph.y = 0;
+    cairo_text_extents_t extents;
+    cairo_glyph_extents(aContext->GetCairo(), &glyph, 1, &extents);
+
+    const Metrics& fontMetrics = GetMetrics();
+    int32_t appUnitsPerDevUnit = aExtents->GetAppUnitsPerDevUnit();
+    if (!aNeedTight && extents.x_bearing >= 0 &&
+        extents.y_bearing >= -fontMetrics.maxAscent &&
+        extents.height + extents.y_bearing <= fontMetrics.maxDescent) {
+        uint32_t appUnitsWidth =
+            uint32_t(ceil((extents.x_bearing + extents.width)*appUnitsPerDevUnit));
+        if (appUnitsWidth < gfxGlyphExtents::INVALID_WIDTH) {
+            aExtents->SetContainedGlyphWidthAppUnits(aGlyphID, uint16_t(appUnitsWidth));
+            return;
+        }
+    }
+#ifdef DEBUG_TEXT_RUN_STORAGE_METRICS
+    if (!aNeedTight) {
+        ++gGlyphExtentsSetupFallBackToTight;
+    }
+#endif
+
+    gfxFloat d2a = appUnitsPerDevUnit;
+    gfxRect bounds(extents.x_bearing*d2a, extents.y_bearing*d2a,
+                   extents.width*d2a, extents.height*d2a);
+    aExtents->SetTightGlyphExtents(aGlyphID, bounds);
+}
+
+// Try to initialize font metrics by reading sfnt tables directly;
+// set mIsValid=TRUE and return TRUE on success.
+// Return FALSE if the gfxFontEntry subclass does not
+// implement GetFontTable(), or for non-sfnt fonts where tables are
+// not available.
+// If this returns TRUE without setting the mIsValid flag, then we -did-
+// apparently find an sfnt, but it was too broken to be used.
+bool
+gfxFont::InitMetricsFromSfntTables(Metrics& aMetrics)
+{
+    mIsValid = false; // font is NOT valid in case of early return
+
+    const uint32_t kHheaTableTag = TRUETYPE_TAG('h','h','e','a');
+    const uint32_t kPostTableTag = TRUETYPE_TAG('p','o','s','t');
+    const uint32_t kOS_2TableTag = TRUETYPE_TAG('O','S','/','2');
+
+    uint32_t len;
+
+    if (mFUnitsConvFactor == 0.0) {
+        // If the conversion factor from FUnits is not yet set,
+        // get the unitsPerEm from the 'head' table via the font entry
+        uint16_t unitsPerEm = GetFontEntry()->UnitsPerEm();
+        if (unitsPerEm == gfxFontEntry::kInvalidUPEM) {
+            return false;
+        }
+        mFUnitsConvFactor = mAdjustedSize / unitsPerEm;
+    }
+
+    // 'hhea' table is required to get vertical extents
+    gfxFontEntry::AutoTable hheaTable(mFontEntry, kHheaTableTag);
+    if (!hheaTable) {
+        return false; // no 'hhea' table -> not an sfnt
+    }
+    const HheaTable* hhea =
+        reinterpret_cast<const HheaTable*>(hb_blob_get_data(hheaTable, &len));
+    if (len < sizeof(HheaTable)) {
+        return false;
+    }
+
+#define SET_UNSIGNED(field,src) aMetrics.field = uint16_t(src) * mFUnitsConvFactor
+#define SET_SIGNED(field,src)   aMetrics.field = int16_t(src) * mFUnitsConvFactor
+
+    SET_UNSIGNED(maxAdvance, hhea->advanceWidthMax);
+    SET_SIGNED(maxAscent, hhea->ascender);
+    SET_SIGNED(maxDescent, -int16_t(hhea->descender));
+    SET_SIGNED(externalLeading, hhea->lineGap);
+
+    // 'post' table is required for underline metrics
+    gfxFontEntry::AutoTable postTable(mFontEntry, kPostTableTag);
+    if (!postTable) {
+        return true; // no 'post' table -> sfnt is not valid
+    }
+    const PostTable *post =
+        reinterpret_cast<const PostTable*>(hb_blob_get_data(postTable, &len));
+    if (len < offsetof(PostTable, underlineThickness) + sizeof(uint16_t)) {
+        return true; // bad post table -> sfnt is not valid
+    }
+
+    SET_SIGNED(underlineOffset, post->underlinePosition);
+    SET_UNSIGNED(underlineSize, post->underlineThickness);
+
+    // 'OS/2' table is optional, if not found we'll estimate xHeight
+    // and aveCharWidth by measuring glyphs
+    gfxFontEntry::AutoTable os2Table(mFontEntry, kOS_2TableTag);
+    if (os2Table) {
+        const OS2Table *os2 =
+            reinterpret_cast<const OS2Table*>(hb_blob_get_data(os2Table, &len));
+        if (len >= offsetof(OS2Table, sxHeight) + sizeof(int16_t) &&
+            uint16_t(os2->version) >= 2) {
+            // version 2 and later includes the x-height field
+            SET_SIGNED(xHeight, os2->sxHeight);
+            // Abs because of negative xHeight seen in Kokonor (Tibetan) font
+            aMetrics.xHeight = Abs(aMetrics.xHeight);
+        }
+        // this should always be present in any valid OS/2 of any version
+        if (len >= offsetof(OS2Table, sTypoLineGap) + sizeof(int16_t)) {
+            SET_SIGNED(aveCharWidth, os2->xAvgCharWidth);
+            SET_SIGNED(subscriptOffset, os2->ySubscriptYOffset);
+            SET_SIGNED(superscriptOffset, os2->ySuperscriptYOffset);
+            SET_SIGNED(strikeoutSize, os2->yStrikeoutSize);
+            SET_SIGNED(strikeoutOffset, os2->yStrikeoutPosition);
+
+            // for fonts with USE_TYPO_METRICS set in the fsSelection field,
+            // and for all OpenType math fonts (having a 'MATH' table),
+            // let the OS/2 sTypo* metrics override those from the hhea table
+            // (see http://www.microsoft.com/typography/otspec/os2.htm#fss)
+            const uint16_t kUseTypoMetricsMask = 1 << 7;
+            if ((uint16_t(os2->fsSelection) & kUseTypoMetricsMask) ||
+                mFontEntry->HasFontTable(TRUETYPE_TAG('M','A','T','H'))) {
+                SET_SIGNED(maxAscent, os2->sTypoAscender);
+                SET_SIGNED(maxDescent, - int16_t(os2->sTypoDescender));
+                SET_SIGNED(externalLeading, os2->sTypoLineGap);
+            }
+        }
+    }
+
+    mIsValid = true;
+
+    return true;
+}
+
+static double
+RoundToNearestMultiple(double aValue, double aFraction)
+{
+    return floor(aValue/aFraction + 0.5) * aFraction;
+}
+
+void gfxFont::CalculateDerivedMetrics(Metrics& aMetrics)
+{
+    aMetrics.maxAscent =
+        ceil(RoundToNearestMultiple(aMetrics.maxAscent, 1/1024.0));
+    aMetrics.maxDescent =
+        ceil(RoundToNearestMultiple(aMetrics.maxDescent, 1/1024.0));
+
+    if (aMetrics.xHeight <= 0) {
+        // only happens if we couldn't find either font metrics
+        // or a char to measure;
+        // pick an arbitrary value that's better than zero
+        aMetrics.xHeight = aMetrics.maxAscent * DEFAULT_XHEIGHT_FACTOR;
+    }
+
+    aMetrics.maxHeight = aMetrics.maxAscent + aMetrics.maxDescent;
+
+    if (aMetrics.maxHeight - aMetrics.emHeight > 0.0) {
+        aMetrics.internalLeading = aMetrics.maxHeight - aMetrics.emHeight;
+    } else {
+        aMetrics.internalLeading = 0.0;
+    }
+
+    aMetrics.emAscent = aMetrics.maxAscent * aMetrics.emHeight
+                            / aMetrics.maxHeight;
+    aMetrics.emDescent = aMetrics.emHeight - aMetrics.emAscent;
+
+    if (GetFontEntry()->IsFixedPitch()) {
+        // Some Quartz fonts are fixed pitch, but there's some glyph with a bigger
+        // advance than the average character width... this forces
+        // those fonts to be recognized like fixed pitch fonts by layout.
+        aMetrics.maxAdvance = aMetrics.aveCharWidth;
+    }
+
+    if (!aMetrics.subscriptOffset) {
+        aMetrics.subscriptOffset = aMetrics.xHeight;
+    }
+    if (!aMetrics.superscriptOffset) {
+        aMetrics.superscriptOffset = aMetrics.xHeight;
+    }
+
+    if (!aMetrics.strikeoutOffset) {
+        aMetrics.strikeoutOffset = aMetrics.xHeight * 0.5;
+    }
+    if (!aMetrics.strikeoutSize) {
+        aMetrics.strikeoutSize = aMetrics.underlineSize;
+    }
+}
+
+void
+gfxFont::SanitizeMetrics(gfxFont::Metrics *aMetrics, bool aIsBadUnderlineFont)
+{
+    // Even if this font size is zero, this font is created with non-zero size.
+    // However, for layout and others, we should return the metrics of zero size font.
+    if (mStyle.size == 0.0) {
+        memset(aMetrics, 0, sizeof(gfxFont::Metrics));
+        return;
+    }
+
+    // MS (P)Gothic and MS (P)Mincho are not having suitable values in their super script offset.
+    // If the values are not suitable, we should use x-height instead of them.
+    // See https://bugzilla.mozilla.org/show_bug.cgi?id=353632
+    if (aMetrics->superscriptOffset <= 0 ||
+        aMetrics->superscriptOffset >= aMetrics->maxAscent) {
+        aMetrics->superscriptOffset = aMetrics->xHeight;
+    }
+    // And also checking the case of sub script offset. The old gfx for win has checked this too.
+    if (aMetrics->subscriptOffset <= 0 ||
+        aMetrics->subscriptOffset >= aMetrics->maxAscent) {
+        aMetrics->subscriptOffset = aMetrics->xHeight;
+    }
+
+    aMetrics->underlineSize = std::max(1.0, aMetrics->underlineSize);
+    aMetrics->strikeoutSize = std::max(1.0, aMetrics->strikeoutSize);
+
+    aMetrics->underlineOffset = std::min(aMetrics->underlineOffset, -1.0);
+
+    if (aMetrics->maxAscent < 1.0) {
+        // We cannot draw strikeout line and overline in the ascent...
+        aMetrics->underlineSize = 0;
+        aMetrics->underlineOffset = 0;
+        aMetrics->strikeoutSize = 0;
+        aMetrics->strikeoutOffset = 0;
+        return;
+    }
+
+    /**
+     * Some CJK fonts have bad underline offset. Therefore, if this is such font,
+     * we need to lower the underline offset to bottom of *em* descent.
+     * However, if this is system font, we should not do this for the rendering compatibility with
+     * another application's UI on the platform.
+     * XXX Should not use this hack if the font size is too small?
+     *     Such text cannot be read, this might be used for tight CSS rendering? (E.g., Acid2)
+     */
+    if (!mStyle.systemFont && aIsBadUnderlineFont) {
+        // First, we need 2 pixels between baseline and underline at least. Because many CJK characters
+        // put their glyphs on the baseline, so, 1 pixel is too close for CJK characters.
+        aMetrics->underlineOffset = std::min(aMetrics->underlineOffset, -2.0);
+
+        // Next, we put the underline to bottom of below of the descent space.
+        if (aMetrics->internalLeading + aMetrics->externalLeading > aMetrics->underlineSize) {
+            aMetrics->underlineOffset = std::min(aMetrics->underlineOffset, -aMetrics->emDescent);
+        } else {
+            aMetrics->underlineOffset = std::min(aMetrics->underlineOffset,
+                                               aMetrics->underlineSize - aMetrics->emDescent);
+        }
+    }
+    // If underline positioned is too far from the text, descent position is preferred so that underline
+    // will stay within the boundary.
+    else if (aMetrics->underlineSize - aMetrics->underlineOffset > aMetrics->maxDescent) {
+        if (aMetrics->underlineSize > aMetrics->maxDescent)
+            aMetrics->underlineSize = std::max(aMetrics->maxDescent, 1.0);
+        // The max underlineOffset is 1px (the min underlineSize is 1px, and min maxDescent is 0px.)
+        aMetrics->underlineOffset = aMetrics->underlineSize - aMetrics->maxDescent;
+    }
+
+    // If strikeout line is overflowed from the ascent, the line should be resized and moved for
+    // that being in the ascent space.
+    // Note that the strikeoutOffset is *middle* of the strikeout line position.
+    gfxFloat halfOfStrikeoutSize = floor(aMetrics->strikeoutSize / 2.0 + 0.5);
+    if (halfOfStrikeoutSize + aMetrics->strikeoutOffset > aMetrics->maxAscent) {
+        if (aMetrics->strikeoutSize > aMetrics->maxAscent) {
+            aMetrics->strikeoutSize = std::max(aMetrics->maxAscent, 1.0);
+            halfOfStrikeoutSize = floor(aMetrics->strikeoutSize / 2.0 + 0.5);
+        }
+        gfxFloat ascent = floor(aMetrics->maxAscent + 0.5);
+        aMetrics->strikeoutOffset = std::max(halfOfStrikeoutSize, ascent / 2.0);
+    }
+
+    // If overline is larger than the ascent, the line should be resized.
+    if (aMetrics->underlineSize > aMetrics->maxAscent) {
+        aMetrics->underlineSize = aMetrics->maxAscent;
+    }
+}
+
+gfxFloat
+gfxFont::SynthesizeSpaceWidth(uint32_t aCh)
+{
+    // return an appropriate width for various Unicode space characters
+    // that we "fake" if they're not actually present in the font;
+    // returns negative value if the char is not a known space.
+    switch (aCh) {
+    case 0x2000:                                 // en quad
+    case 0x2002: return GetAdjustedSize() / 2;   // en space
+    case 0x2001:                                 // em quad
+    case 0x2003: return GetAdjustedSize();       // em space
+    case 0x2004: return GetAdjustedSize() / 3;   // three-per-em space
+    case 0x2005: return GetAdjustedSize() / 4;   // four-per-em space
+    case 0x2006: return GetAdjustedSize() / 6;   // six-per-em space
+    case 0x2007: return GetMetrics().zeroOrAveCharWidth; // figure space
+    case 0x2008: return GetMetrics().spaceWidth; // punctuation space 
+    case 0x2009: return GetAdjustedSize() / 5;   // thin space
+    case 0x200a: return GetAdjustedSize() / 10;  // hair space
+    case 0x202f: return GetAdjustedSize() / 5;   // narrow no-break space
+    default: return -1.0;
+    }
+}
+
+/*static*/ size_t
+gfxFont::WordCacheEntrySizeOfExcludingThis(CacheHashEntry*   aHashEntry,
+                                           MallocSizeOf aMallocSizeOf,
+                                           void*             aUserArg)
+{
+    return aMallocSizeOf(aHashEntry->mShapedWord.get());
+}
+
+void
+gfxFont::AddSizeOfExcludingThis(MallocSizeOf aMallocSizeOf,
+                                FontCacheSizes* aSizes) const
+{
+    for (uint32_t i = 0; i < mGlyphExtentsArray.Length(); ++i) {
+        aSizes->mFontInstances +=
+            mGlyphExtentsArray[i]->SizeOfIncludingThis(aMallocSizeOf);
+    }
+    if (mWordCache) {
+        aSizes->mShapedWords +=
+            mWordCache->SizeOfExcludingThis(WordCacheEntrySizeOfExcludingThis,
+                                            aMallocSizeOf);
+    }
+}
+
+void
+gfxFont::AddSizeOfIncludingThis(MallocSizeOf aMallocSizeOf,
+                                FontCacheSizes* aSizes) const
+{
+    aSizes->mFontInstances += aMallocSizeOf(this);
+    AddSizeOfExcludingThis(aMallocSizeOf, aSizes);
+}
+
+void
+gfxFont::AddGlyphChangeObserver(GlyphChangeObserver *aObserver)
+{
+    if (!mGlyphChangeObservers) {
+        mGlyphChangeObservers = new nsTHashtable<nsPtrHashKey<GlyphChangeObserver> >;
+    }
+    mGlyphChangeObservers->PutEntry(aObserver);
+}
+
+void
+gfxFont::RemoveGlyphChangeObserver(GlyphChangeObserver *aObserver)
+{
+    NS_ASSERTION(mGlyphChangeObservers, "No observers registered");
+    NS_ASSERTION(mGlyphChangeObservers->Contains(aObserver), "Observer not registered");
+    mGlyphChangeObservers->RemoveEntry(aObserver);
+}
+
+gfxGlyphExtents::~gfxGlyphExtents()
+{
+#ifdef DEBUG_TEXT_RUN_STORAGE_METRICS
+    gGlyphExtentsWidthsTotalSize +=
+        mContainedGlyphWidths.SizeOfExcludingThis(&FontCacheMallocSizeOf);
+    gGlyphExtentsCount++;
+#endif
+    MOZ_COUNT_DTOR(gfxGlyphExtents);
+}
+
+bool
+gfxGlyphExtents::GetTightGlyphExtentsAppUnits(gfxFont *aFont,
+    gfxContext *aContext, uint32_t aGlyphID, gfxRect *aExtents)
+{
+    HashEntry *entry = mTightGlyphExtents.GetEntry(aGlyphID);
+    if (!entry) {
+        if (!aContext) {
+            NS_WARNING("Could not get glyph extents (no aContext)");
+            return false;
+        }
+
+        if (aFont->SetupCairoFont(aContext)) {
+#ifdef DEBUG_TEXT_RUN_STORAGE_METRICS
+            ++gGlyphExtentsSetupLazyTight;
+#endif
+            aFont->SetupGlyphExtents(aContext, aGlyphID, true, this);
+            entry = mTightGlyphExtents.GetEntry(aGlyphID);
+        }
+        if (!entry) {
+            NS_WARNING("Could not get glyph extents");
+            return false;
+        }
+    }
+
+    *aExtents = gfxRect(entry->x, entry->y, entry->width, entry->height);
+    return true;
+}
+
+gfxGlyphExtents::GlyphWidths::~GlyphWidths()
+{
+    uint32_t i, count = mBlocks.Length();
+    for (i = 0; i < count; ++i) {
+        uintptr_t bits = mBlocks[i];
+        if (bits && !(bits & 0x1)) {
+            delete[] reinterpret_cast<uint16_t *>(bits);
+        }
+    }
+}
+
+uint32_t
+gfxGlyphExtents::GlyphWidths::SizeOfExcludingThis(MallocSizeOf aMallocSizeOf) const
+{
+    uint32_t i;
+    uint32_t size = mBlocks.SizeOfExcludingThis(aMallocSizeOf);
+    for (i = 0; i < mBlocks.Length(); ++i) {
+        uintptr_t bits = mBlocks[i];
+        if (bits && !(bits & 0x1)) {
+            size += aMallocSizeOf(reinterpret_cast<void*>(bits));
+        }
+    }
+    return size;
+}
+
+void
+gfxGlyphExtents::GlyphWidths::Set(uint32_t aGlyphID, uint16_t aWidth)
+{
+    uint32_t block = aGlyphID >> BLOCK_SIZE_BITS;
+    uint32_t len = mBlocks.Length();
+    if (block >= len) {
+        uintptr_t *elems = mBlocks.AppendElements(block + 1 - len);
+        if (!elems)
+            return;
+        memset(elems, 0, sizeof(uintptr_t)*(block + 1 - len));
+    }
+
+    uintptr_t bits = mBlocks[block];
+    uint32_t glyphOffset = aGlyphID & (BLOCK_SIZE - 1);
+    if (!bits) {
+        mBlocks[block] = MakeSingle(glyphOffset, aWidth);
+        return;
+    }
+
+    uint16_t *newBlock;
+    if (bits & 0x1) {
+        // Expand the block to a real block. We could avoid this by checking
+        // glyphOffset == GetGlyphOffset(bits), but that never happens so don't bother
+        newBlock = new uint16_t[BLOCK_SIZE];
+        if (!newBlock)
+            return;
+        uint32_t i;
+        for (i = 0; i < BLOCK_SIZE; ++i) {
+            newBlock[i] = INVALID_WIDTH;
+        }
+        newBlock[GetGlyphOffset(bits)] = GetWidth(bits);
+        mBlocks[block] = reinterpret_cast<uintptr_t>(newBlock);
+    } else {
+        newBlock = reinterpret_cast<uint16_t *>(bits);
+    }
+    newBlock[glyphOffset] = aWidth;
+}
+
+void
+gfxGlyphExtents::SetTightGlyphExtents(uint32_t aGlyphID, const gfxRect& aExtentsAppUnits)
+{
+    HashEntry *entry = mTightGlyphExtents.PutEntry(aGlyphID);
+    if (!entry)
+        return;
+    entry->x = aExtentsAppUnits.X();
+    entry->y = aExtentsAppUnits.Y();
+    entry->width = aExtentsAppUnits.Width();
+    entry->height = aExtentsAppUnits.Height();
+}
+
+size_t
+gfxGlyphExtents::SizeOfExcludingThis(MallocSizeOf aMallocSizeOf) const
+{
+    return mContainedGlyphWidths.SizeOfExcludingThis(aMallocSizeOf) +
+        mTightGlyphExtents.SizeOfExcludingThis(nullptr, aMallocSizeOf);
+}
+
+size_t
+gfxGlyphExtents::SizeOfIncludingThis(MallocSizeOf aMallocSizeOf) const
+{
+    return aMallocSizeOf(this) + SizeOfExcludingThis(aMallocSizeOf);
+}
+
+gfxFontGroup::gfxFontGroup(const nsAString& aFamilies,
+                           const gfxFontStyle *aStyle,
+                           gfxUserFontSet *aUserFontSet)
+    : mFamilies(aFamilies)
+    , mStyle(*aStyle)
+    , mUnderlineOffset(UNDERLINE_OFFSET_NOT_SET)
+    , mHyphenWidth(-1)
+    , mUserFontSet(aUserFontSet)
+    , mTextPerf(nullptr)
+    , mPageLang(gfxPlatform::GetFontPrefLangFor(aStyle->language))
+    , mSkipDrawing(false)
+{
+    // We don't use SetUserFontSet() here, as we want to unconditionally call
+    // BuildFontList() rather than only do UpdateFontList() if it changed.
+    mCurrGeneration = GetGeneration();
+    BuildFontList();
+}
+
+void
+gfxFontGroup::BuildFontList()
+{
+// "#if" to be removed once all platforms are moved to gfxPlatformFontList interface
+// and subclasses of gfxFontGroup eliminated
+#if defined(XP_MACOSX) || defined(XP_WIN) || defined(ANDROID)
+    ForEachFont(FindPlatformFont, this);
+
+    if (mFonts.Length() == 0) {
+        bool needsBold;
+        gfxPlatformFontList *pfl = gfxPlatformFontList::PlatformFontList();
+        gfxFontFamily *defaultFamily = pfl->GetDefaultFont(&mStyle);
+        NS_ASSERTION(defaultFamily,
+                     "invalid default font returned by GetDefaultFont");
+
+        if (defaultFamily) {
+            gfxFontEntry *fe = defaultFamily->FindFontForStyle(mStyle,
+                                                               needsBold);
+            if (fe) {
+                nsRefPtr<gfxFont> font = fe->FindOrMakeFont(&mStyle,
+                                                            needsBold);
+                if (font) {
+                    mFonts.AppendElement(FamilyFace(defaultFamily, font));
+                }
+            }
+        }
+
+        if (mFonts.Length() == 0) {
+            // Try for a "font of last resort...."
+            // Because an empty font list would be Really Bad for later code
+            // that assumes it will be able to get valid metrics for layout,
+            // just look for the first usable font and put in the list.
+            // (see bug 554544)
+            nsAutoTArray<nsRefPtr<gfxFontFamily>,200> families;
+            pfl->GetFontFamilyList(families);
+            uint32_t count = families.Length();
+            for (uint32_t i = 0; i < count; ++i) {
+                gfxFontEntry *fe = families[i]->FindFontForStyle(mStyle,
+                                                                 needsBold);
+                if (fe) {
+                    nsRefPtr<gfxFont> font = fe->FindOrMakeFont(&mStyle,
+                                                                needsBold);
+                    if (font) {
+                        mFonts.AppendElement(FamilyFace(families[i], font));
+                        break;
+                    }
+                }
+            }
+        }
+
+        if (mFonts.Length() == 0) {
+            // an empty font list at this point is fatal; we're not going to
+            // be able to do even the most basic layout operations
+            char msg[256]; // CHECK buffer length if revising message below
+            sprintf(msg, "unable to find a usable font (%.220s)",
+                    NS_ConvertUTF16toUTF8(mFamilies).get());
+            NS_RUNTIMEABORT(msg);
+        }
+    }
+
+    if (!mStyle.systemFont) {
+        uint32_t count = mFonts.Length();
+        for (uint32_t i = 0; i < count; ++i) {
+            gfxFont* font = mFonts[i].Font();
+            if (font->GetFontEntry()->mIsBadUnderlineFont) {
+                gfxFloat first = mFonts[0].Font()->GetMetrics().underlineOffset;
+                gfxFloat bad = font->GetMetrics().underlineOffset;
+                mUnderlineOffset = std::min(first, bad);
+                break;
+            }
+        }
+    }
+#endif
+}
+
+bool
+gfxFontGroup::FindPlatformFont(const nsAString& aName,
+                               const nsACString& aGenericName,
+                               bool aUseFontSet,
+                               void *aClosure)
+{
+    gfxFontGroup *fontGroup = static_cast<gfxFontGroup*>(aClosure);
+    const gfxFontStyle *fontStyle = fontGroup->GetStyle();
+
+    bool needsBold;
+    gfxFontFamily *family = nullptr;
+    gfxFontEntry *fe = nullptr;
+
+    if (aUseFontSet) {
+        // First, look up in the user font set...
+        // If the fontSet matches the family, we must not look for a platform
+        // font of the same name, even if we fail to actually get a fontEntry
+        // here; we'll fall back to the next name in the CSS font-family list.
+        gfxUserFontSet *fs = fontGroup->GetUserFontSet();
+        if (fs) {
+            // If the fontSet matches the family, but the font has not yet finished
+            // loading (nor has its load timeout fired), the fontGroup should wait
+            // for the download, and not actually draw its text yet.
+            family = fs->GetFamily(aName);
+            if (family) {
+                bool waitForUserFont = false;
+                fe = fs->FindFontEntry(family, *fontStyle,
+                                       needsBold, waitForUserFont);
+                if (!fe && waitForUserFont) {
+                    fontGroup->mSkipDrawing = true;
+                }
+            }
+        }
+    }
+
+    // Not known in the user font set ==> check system fonts
+    // XXX: Fallback is bad..
+    if (!family) {
+        gfxPlatformFontList *fontList = gfxPlatformFontList::PlatformFontList();
+        family = fontList->FindFamily(aName);
+        if (family) {
+            fe = family->FindFontForStyle(*fontStyle, needsBold);
+        }
+    }
+
+    // add to the font group, unless it's already there
+    if (fe && !fontGroup->HasFont(fe)) {
+        nsRefPtr<gfxFont> font = fe->FindOrMakeFont(fontStyle, needsBold);
+        if (font) {
+            fontGroup->mFonts.AppendElement(FamilyFace(family, font));
+        }
+    }
+
+    return true;
+}
+
+bool
+gfxFontGroup::HasFont(const gfxFontEntry *aFontEntry)
+{
+    uint32_t count = mFonts.Length();
+    for (uint32_t i = 0; i < count; ++i) {
+        if (mFonts[i].Font()->GetFontEntry() == aFontEntry)
+            return true;
+    }
+    return false;
+}
+
+gfxFontGroup::~gfxFontGroup()
+{
+    mFonts.Clear();
+}
+
+gfxFontGroup *
+gfxFontGroup::Copy(const gfxFontStyle *aStyle)
+{
+    gfxFontGroup *fg = new gfxFontGroup(mFamilies, aStyle, mUserFontSet);
+    fg->SetTextPerfMetrics(mTextPerf);
+    return fg;
+}
+
+bool 
+gfxFontGroup::IsInvalidChar(uint8_t ch)
+{
+    return ((ch & 0x7f) < 0x20 || ch == 0x7f);
+}
+
+bool 
+gfxFontGroup::IsInvalidChar(char16_t ch)
+{
+    // All printable 7-bit ASCII values are OK
+    if (ch >= ' ' && ch < 0x7f) {
+        return false;
+    }
+    // No point in sending non-printing control chars through font shaping
+    if (ch <= 0x9f) {
+        return true;
+    }
+    return (((ch & 0xFF00) == 0x2000 /* Unicode control character */ &&
+             (ch == 0x200B/*ZWSP*/ || ch == 0x2028/*LSEP*/ || ch == 0x2029/*PSEP*/)) ||
+            IsBidiControl(ch));
+}
+
+bool
+gfxFontGroup::ForEachFont(FontCreationCallback fc,
+                          void *closure)
+{
+    return ForEachFontInternal(mFamilies, mStyle.language,
+                               true, true, true, fc, closure);
+}
+
+bool
+gfxFontGroup::ForEachFont(const nsAString& aFamilies,
+                          nsIAtom *aLanguage,
+                          FontCreationCallback fc,
+                          void *closure)
+{
+    return ForEachFontInternal(aFamilies, aLanguage,
+                               false, true, true, fc, closure);
+}
+
+struct ResolveData {
+    ResolveData(gfxFontGroup::FontCreationCallback aCallback,
+                nsACString& aGenericFamily,
+                bool aUseFontSet,
+                void *aClosure) :
+        mCallback(aCallback),
+        mGenericFamily(aGenericFamily),
+        mUseFontSet(aUseFontSet),
+        mClosure(aClosure) {
+    }
+    gfxFontGroup::FontCreationCallback mCallback;
+    nsCString mGenericFamily;
+    bool mUseFontSet;
+    void *mClosure;
+};
+
+bool
+gfxFontGroup::ForEachFontInternal(const nsAString& aFamilies,
+                                  nsIAtom *aLanguage,
+                                  bool aResolveGeneric,
+                                  bool aResolveFontName,
+                                  bool aUseFontSet,
+                                  FontCreationCallback fc,
+                                  void *closure)
+{
+    const char16_t kSingleQuote  = char16_t('\'');
+    const char16_t kDoubleQuote  = char16_t('\"');
+    const char16_t kComma        = char16_t(',');
+
+    nsIAtom *groupAtom = nullptr;
+    nsAutoCString groupString;
+    if (aLanguage) {
+        if (!gLangService) {
+            CallGetService(NS_LANGUAGEATOMSERVICE_CONTRACTID, &gLangService);
+        }
+        if (gLangService) {
+            nsresult rv;
+            groupAtom = gLangService->GetLanguageGroup(aLanguage, &rv);
+        }
+    }
+    if (!groupAtom) {
+        groupAtom = nsGkAtoms::Unicode;
+    }
+    groupAtom->ToUTF8String(groupString);
+
+    nsPromiseFlatString families(aFamilies);
+    const char16_t *p, *p_end;
+    families.BeginReading(p);
+    families.EndReading(p_end);
+    nsAutoString family;
+    nsAutoCString lcFamily;
+    nsAutoString genericFamily;
+
+    while (p < p_end) {
+        while (nsCRT::IsAsciiSpace(*p) || *p == kComma)
+            if (++p == p_end)
+                return true;
+
+        bool generic;
+        if (*p == kSingleQuote || *p == kDoubleQuote) {
+            // quoted font family
+            char16_t quoteMark = *p;
+            if (++p == p_end)
+                return true;
+            const char16_t *nameStart = p;
+
+            // XXX What about CSS character escapes?
+            while (*p != quoteMark)
+                if (++p == p_end)
+                    return true;
+
+            family = Substring(nameStart, p);
+            generic = false;
+            genericFamily.SetIsVoid(true);
+
+            while (++p != p_end && *p != kComma)
+                /* nothing */ ;
+
+        } else {
+            // unquoted font family
+            const char16_t *nameStart = p;
+            while (++p != p_end && *p != kComma)
+                /* nothing */ ;
+
+            family = Substring(nameStart, p);
+            family.CompressWhitespace(false, true);
+
+            if (aResolveGeneric &&
+                (family.LowerCaseEqualsLiteral("serif") ||
+                 family.LowerCaseEqualsLiteral("sans-serif") ||
+                 family.LowerCaseEqualsLiteral("monospace") ||
+                 family.LowerCaseEqualsLiteral("cursive") ||
+                 family.LowerCaseEqualsLiteral("fantasy")))
+            {
+                generic = true;
+
+                ToLowerCase(NS_LossyConvertUTF16toASCII(family), lcFamily);
+
+                nsAutoCString prefName("font.name.");
+                prefName.Append(lcFamily);
+                prefName.AppendLiteral(".");
+                prefName.Append(groupString);
+
+                nsAdoptingString value = Preferences::GetString(prefName.get());
+                if (value) {
+                    CopyASCIItoUTF16(lcFamily, genericFamily);
+                    family = value;
+                }
+            } else {
+                generic = false;
+                genericFamily.SetIsVoid(true);
+            }
+        }
+
+        NS_LossyConvertUTF16toASCII gf(genericFamily);
+        if (generic) {
+            ForEachFontInternal(family, groupAtom, false,
+                                aResolveFontName, false,
+                                fc, closure);
+        } else if (!family.IsEmpty()) {
+            if (aResolveFontName) {
+                ResolveData data(fc, gf, aUseFontSet, closure);
+                bool aborted = false, needsBold;
+                nsresult rv = NS_OK;
+                bool foundFamily = false;
+                bool waitForUserFont = false;
+                gfxFontEntry *fe = nullptr;
+                if (aUseFontSet && mUserFontSet) {
+                    gfxFontFamily *fam = mUserFontSet->GetFamily(family);
+                    if (fam) {
+                        fe = mUserFontSet->FindFontEntry(fam, mStyle,
+                                                         needsBold,
+                                                         waitForUserFont);
+                    }
+                }
+                if (fe) {
+                    gfxFontGroup::FontResolverProc(family, &data);
+                } else {
+                    if (waitForUserFont) {
+                        mSkipDrawing = true;
+                    }
+                    if (!foundFamily) {
+                        gfxPlatform *pf = gfxPlatform::GetPlatform();
+                        // XXX: Fallback is bad
+                        rv = pf->ResolveFontName(family,
+                                                 gfxFontGroup::FontResolverProc,
+                                                 &data, aborted);
+                    }
+                }
+                if (NS_FAILED(rv) || aborted)
+                    return false;
+            }
+            else {
+                if (!fc(family, gf, aUseFontSet, closure))
+                    return false;
+            }
+        }
+
+        if (generic && aResolveGeneric) {
+            nsAutoCString prefName("font.name-list.");
+            prefName.Append(lcFamily);
+            prefName.AppendLiteral(".");
+            prefName.Append(groupString);
+            nsAdoptingString value = Preferences::GetString(prefName.get());
+            if (value) {
+                ForEachFontInternal(value, groupAtom, false,
+                                    aResolveFontName, false,
+                                    fc, closure);
+            }
+        }
+
+        ++p; // may advance past p_end
+    }
+
+    return true;
+}
+
+bool
+gfxFontGroup::FontResolverProc(const nsAString& aName, void *aClosure)
+{
+    ResolveData *data = reinterpret_cast<ResolveData*>(aClosure);
+    return (data->mCallback)(aName, data->mGenericFamily, data->mUseFontSet,
+                             data->mClosure);
+}
+
+gfxTextRun *
+gfxFontGroup::MakeEmptyTextRun(const Parameters *aParams, uint32_t aFlags)
+{
+    aFlags |= TEXT_IS_8BIT | TEXT_IS_ASCII | TEXT_IS_PERSISTENT;
+    return gfxTextRun::Create(aParams, 0, this, aFlags);
+}
+
+gfxTextRun *
+gfxFontGroup::MakeSpaceTextRun(const Parameters *aParams, uint32_t aFlags)
+{
+    aFlags |= TEXT_IS_8BIT | TEXT_IS_ASCII | TEXT_IS_PERSISTENT;
+
+    gfxTextRun *textRun = gfxTextRun::Create(aParams, 1, this, aFlags);
+    if (!textRun) {
+        return nullptr;
+    }
+
+    gfxFont *font = GetFontAt(0);
+    if (MOZ_UNLIKELY(GetStyle()->size == 0)) {
+        // Short-circuit for size-0 fonts, as Windows and ATSUI can't handle
+        // them, and always create at least size 1 fonts, i.e. they still
+        // render something for size 0 fonts.
+        textRun->AddGlyphRun(font, gfxTextRange::kFontGroup, 0, false);
+    }
+    else {
+        if (font->GetSpaceGlyph()) {
+            // Normally, the font has a cached space glyph, so we can avoid
+            // the cost of calling FindFontForChar.
+            textRun->SetSpaceGlyph(font, aParams->mContext, 0);
+        } else {
+            // In case the primary font doesn't have <space> (bug 970891),
+            // find one that does.
+            uint8_t matchType;
+            nsRefPtr<gfxFont> spaceFont =
+                FindFontForChar(' ', 0, MOZ_SCRIPT_LATIN, nullptr, &matchType);
+            if (spaceFont) {
+                textRun->SetSpaceGlyph(spaceFont, aParams->mContext, 0);
+            }
+        }
+    }
+
+    // Note that the gfxGlyphExtents glyph bounds storage for the font will
+    // always contain an entry for the font's space glyph, so we don't have
+    // to call FetchGlyphExtents here.
+    return textRun;
+}
+
+gfxTextRun *
+gfxFontGroup::MakeBlankTextRun(uint32_t aLength,
+                               const Parameters *aParams, uint32_t aFlags)
+{
+    gfxTextRun *textRun =
+        gfxTextRun::Create(aParams, aLength, this, aFlags);
+    if (!textRun) {
+        return nullptr;
+    }
+
+    textRun->AddGlyphRun(GetFontAt(0), gfxTextRange::kFontGroup, 0, false);
+    return textRun;
+}
+
+gfxTextRun *
+gfxFontGroup::MakeHyphenTextRun(gfxContext *aCtx, uint32_t aAppUnitsPerDevUnit)
+{
+    // only use U+2010 if it is supported by the first font in the group;
+    // it's better to use ASCII '-' from the primary font than to fall back to
+    // U+2010 from some other, possibly poorly-matching face
+    static const char16_t hyphen = 0x2010;
+    gfxFont *font = GetFontAt(0);
+    if (font && font->HasCharacter(hyphen)) {
+        return MakeTextRun(&hyphen, 1, aCtx, aAppUnitsPerDevUnit,
+                           gfxFontGroup::TEXT_IS_PERSISTENT);
+    }
+
+    static const uint8_t dash = '-';
+    return MakeTextRun(&dash, 1, aCtx, aAppUnitsPerDevUnit,
+                       gfxFontGroup::TEXT_IS_PERSISTENT);
+}
+
+gfxFloat
+gfxFontGroup::GetHyphenWidth(gfxTextRun::PropertyProvider *aProvider)
+{
+    if (mHyphenWidth < 0) {
+        nsRefPtr<gfxContext> ctx(aProvider->GetContext());
+        if (ctx) {
+            nsAutoPtr<gfxTextRun>
+                hyphRun(MakeHyphenTextRun(ctx,
+                                          aProvider->GetAppUnitsPerDevUnit()));
+            mHyphenWidth = hyphRun.get() ?
+                hyphRun->GetAdvanceWidth(0, hyphRun->GetLength(), nullptr) : 0;
+        }
+    }
+    return mHyphenWidth;
+}
+
+gfxTextRun *
+gfxFontGroup::MakeTextRun(const uint8_t *aString, uint32_t aLength,
+                          const Parameters *aParams, uint32_t aFlags)
+{
+    if (aLength == 0) {
+        return MakeEmptyTextRun(aParams, aFlags);
+    }
+    if (aLength == 1 && aString[0] == ' ') {
+        return MakeSpaceTextRun(aParams, aFlags);
+    }
+
+    aFlags |= TEXT_IS_8BIT;
+
+    if (GetStyle()->size == 0) {
+        // Short-circuit for size-0 fonts, as Windows and ATSUI can't handle
+        // them, and always create at least size 1 fonts, i.e. they still
+        // render something for size 0 fonts.
+        return MakeBlankTextRun(aLength, aParams, aFlags);
+    }
+
+    gfxTextRun *textRun = gfxTextRun::Create(aParams, aLength,
+                                             this, aFlags);
+    if (!textRun) {
+        return nullptr;
+    }
+
+    InitTextRun(aParams->mContext, textRun, aString, aLength);
+
+    textRun->FetchGlyphExtents(aParams->mContext);
+
+    return textRun;
+}
+
+gfxTextRun *
+gfxFontGroup::MakeTextRun(const char16_t *aString, uint32_t aLength,
+                          const Parameters *aParams, uint32_t aFlags)
+{
+    if (aLength == 0) {
+        return MakeEmptyTextRun(aParams, aFlags);
+    }
+    if (aLength == 1 && aString[0] == ' ') {
+        return MakeSpaceTextRun(aParams, aFlags);
+    }
+    if (GetStyle()->size == 0) {
+        return MakeBlankTextRun(aLength, aParams, aFlags);
+    }
+
+    gfxTextRun *textRun = gfxTextRun::Create(aParams, aLength,
+                                             this, aFlags);
+    if (!textRun) {
+        return nullptr;
+    }
+
+    InitTextRun(aParams->mContext, textRun, aString, aLength);
+
+    textRun->FetchGlyphExtents(aParams->mContext);
+
+    return textRun;
+}
+
+template<typename T>
+void
+gfxFontGroup::InitTextRun(gfxContext *aContext,
+                          gfxTextRun *aTextRun,
+                          const T *aString,
+                          uint32_t aLength)
+{
+    NS_ASSERTION(aLength > 0, "don't call InitTextRun for a zero-length run");
+
+    // we need to do numeral processing even on 8-bit text,
+    // in case we're converting Western to Hindi/Arabic digits
+    int32_t numOption = gfxPlatform::GetPlatform()->GetBidiNumeralOption();
+    nsAutoArrayPtr<char16_t> transformedString;
+    if (numOption != IBMBIDI_NUMERAL_NOMINAL) {
+        // scan the string for numerals that may need to be transformed;
+        // if we find any, we'll make a local copy here and use that for
+        // font matching and glyph generation/shaping
+        bool prevIsArabic =
+            (aTextRun->GetFlags() & gfxTextRunFactory::TEXT_INCOMING_ARABICCHAR) != 0;
+        for (uint32_t i = 0; i < aLength; ++i) {
+            char16_t origCh = aString[i];
+            char16_t newCh = HandleNumberInChar(origCh, prevIsArabic, numOption);
+            if (newCh != origCh) {
+                if (!transformedString) {
+                    transformedString = new char16_t[aLength];
+                    if (sizeof(T) == sizeof(char16_t)) {
+                        memcpy(transformedString.get(), aString, i * sizeof(char16_t));
+                    } else {
+                        for (uint32_t j = 0; j < i; ++j) {
+                            transformedString[j] = aString[j];
+                        }
+                    }
+                }
+            }
+            if (transformedString) {
+                transformedString[i] = newCh;
+            }
+            prevIsArabic = IS_ARABIC_CHAR(newCh);
+        }
+    }
+
+#ifdef PR_LOGGING
+    PRLogModuleInfo *log = (mStyle.systemFont ?
+                            gfxPlatform::GetLog(eGfxLog_textrunui) :
+                            gfxPlatform::GetLog(eGfxLog_textrun));
+#endif
+
+    if (sizeof(T) == sizeof(uint8_t) && !transformedString) {
+
+#ifdef PR_LOGGING
+        if (MOZ_UNLIKELY(PR_LOG_TEST(log, PR_LOG_WARNING))) {
+            nsAutoCString lang;
+            mStyle.language->ToUTF8String(lang);
+            nsAutoCString str((const char*)aString, aLength);
+            PR_LOG(log, PR_LOG_WARNING,\
+                   ("(%s) fontgroup: [%s] lang: %s script: %d len %d "
+                    "weight: %d width: %d style: %s size: %6.2f %d-byte "
+                    "TEXTRUN [%s] ENDTEXTRUN\n",
+                    (mStyle.systemFont ? "textrunui" : "textrun"),
+                    NS_ConvertUTF16toUTF8(mFamilies).get(),
+                    lang.get(), MOZ_SCRIPT_LATIN, aLength,
+                    uint32_t(mStyle.weight), uint32_t(mStyle.stretch),
+                    (mStyle.style & NS_FONT_STYLE_ITALIC ? "italic" :
+                    (mStyle.style & NS_FONT_STYLE_OBLIQUE ? "oblique" :
+                                                            "normal")),
+                    mStyle.size,
+                    sizeof(T),
+                    str.get()));
+        }
+#endif
+
+        // the text is still purely 8-bit; bypass the script-run itemizer
+        // and treat it as a single Latin run
+        InitScriptRun(aContext, aTextRun, aString,
+                      0, aLength, MOZ_SCRIPT_LATIN);
+    } else {
+        const char16_t *textPtr;
+        if (transformedString) {
+            textPtr = transformedString.get();
+        } else {
+            // typecast to avoid compilation error for the 8-bit version,
+            // even though this is dead code in that case
+            textPtr = reinterpret_cast<const char16_t*>(aString);
+        }
+
+        // split into script runs so that script can potentially influence
+        // the font matching process below
+        gfxScriptItemizer scriptRuns(textPtr, aLength);
+
+        uint32_t runStart = 0, runLimit = aLength;
+        int32_t runScript = MOZ_SCRIPT_LATIN;
+        while (scriptRuns.Next(runStart, runLimit, runScript)) {
+
+#ifdef PR_LOGGING
+            if (MOZ_UNLIKELY(PR_LOG_TEST(log, PR_LOG_WARNING))) {
+                nsAutoCString lang;
+                mStyle.language->ToUTF8String(lang);
+                uint32_t runLen = runLimit - runStart;
+                PR_LOG(log, PR_LOG_WARNING,\
+                       ("(%s) fontgroup: [%s] lang: %s script: %d len %d "
+                        "weight: %d width: %d style: %s size: %6.2f %d-byte "
+                        "TEXTRUN [%s] ENDTEXTRUN\n",
+                        (mStyle.systemFont ? "textrunui" : "textrun"),
+                        NS_ConvertUTF16toUTF8(mFamilies).get(),
+                        lang.get(), runScript, runLen,
+                        uint32_t(mStyle.weight), uint32_t(mStyle.stretch),
+                        (mStyle.style & NS_FONT_STYLE_ITALIC ? "italic" :
+                        (mStyle.style & NS_FONT_STYLE_OBLIQUE ? "oblique" :
+                                                                "normal")),
+                        mStyle.size,
+                        sizeof(T),
+                        NS_ConvertUTF16toUTF8(textPtr + runStart, runLen).get()));
+            }
+#endif
+
+            InitScriptRun(aContext, aTextRun, textPtr,
+                          runStart, runLimit, runScript);
+        }
+    }
+
+    if (sizeof(T) == sizeof(char16_t) && aLength > 0) {
+        gfxTextRun::CompressedGlyph *glyph = aTextRun->GetCharacterGlyphs();
+        if (!glyph->IsSimpleGlyph()) {
+            glyph->SetClusterStart(true);
+        }
+    }
+
+    // It's possible for CoreText to omit glyph runs if it decides they contain
+    // only invisibles (e.g., U+FEFF, see reftest 474417-1). In this case, we
+    // need to eliminate them from the glyph run array to avoid drawing "partial
+    // ligatures" with the wrong font.
+    // We don't do this during InitScriptRun (or gfxFont::InitTextRun) because
+    // it will iterate back over all glyphruns in the textrun, which leads to
+    // pathologically-bad perf in the case where a textrun contains many script
+    // changes (see bug 680402) - we'd end up re-sanitizing all the earlier runs
+    // every time a new script subrun is processed.
+    aTextRun->SanitizeGlyphRuns();
+
+    aTextRun->SortGlyphRuns();
+}
+
+template<typename T>
+void
+gfxFontGroup::InitScriptRun(gfxContext *aContext,
+                            gfxTextRun *aTextRun,
+                            const T *aString,
+                            uint32_t aScriptRunStart,
+                            uint32_t aScriptRunEnd,
+                            int32_t aRunScript)
+{
+    NS_ASSERTION(aScriptRunEnd > aScriptRunStart,
+                 "don't call InitScriptRun for a zero-length run");
+
+    gfxFont *mainFont = GetFontAt(0);
+
+    uint32_t runStart = aScriptRunStart;
+    nsAutoTArray<gfxTextRange,3> fontRanges;
+    ComputeRanges(fontRanges, aString + aScriptRunStart,
+                  aScriptRunEnd - aScriptRunStart, aRunScript);
+    uint32_t numRanges = fontRanges.Length();
+
+    for (uint32_t r = 0; r < numRanges; r++) {
+        const gfxTextRange& range = fontRanges[r];
+        uint32_t matchedLength = range.Length();
+        gfxFont *matchedFont = range.font;
+
+        // create the glyph run for this range
+        if (matchedFont) {
+            aTextRun->AddGlyphRun(matchedFont, range.matchType,
+                                  runStart, (matchedLength > 0));
+            // do glyph layout and record the resulting positioned glyphs
+            if (!matchedFont->SplitAndInitTextRun(aContext, aTextRun, aString,
+                                                  runStart, matchedLength,
+                                                  aRunScript)) {
+                // glyph layout failed! treat as missing glyphs
+                matchedFont = nullptr;
+            }
+        } else {
+            aTextRun->AddGlyphRun(mainFont, gfxTextRange::kFontGroup,
+                                  runStart, (matchedLength > 0));
+        }
+
+        if (!matchedFont) {
+            // We need to set cluster boundaries (and mark spaces) so that
+            // surrogate pairs, combining characters, etc behave properly,
+            // even if we don't have glyphs for them
+            aTextRun->SetupClusterBoundaries(runStart, aString + runStart,
+                                             matchedLength);
+
+            // various "missing" characters may need special handling,
+            // so we check for them here
+            uint32_t runLimit = runStart + matchedLength;
+            for (uint32_t index = runStart; index < runLimit; index++) {
+                T ch = aString[index];
+
+                // tab and newline are not to be displayed as hexboxes,
+                // but do need to be recorded in the textrun
+                if (ch == '\n') {
+                    aTextRun->SetIsNewline(index);
+                    continue;
+                }
+                if (ch == '\t') {
+                    aTextRun->SetIsTab(index);
+                    continue;
+                }
+
+                // for 16-bit textruns only, check for surrogate pairs and
+                // special Unicode spaces; omit these checks in 8-bit runs
+                if (sizeof(T) == sizeof(char16_t)) {
+                    if (NS_IS_HIGH_SURROGATE(ch) &&
+                        index + 1 < aScriptRunEnd &&
+                        NS_IS_LOW_SURROGATE(aString[index + 1]))
+                    {
+                        aTextRun->SetMissingGlyph(index,
+                                                  SURROGATE_TO_UCS4(ch,
+                                                                    aString[index + 1]),
+                                                  mainFont);
+                        index++;
+                        continue;
+                    }
+
+                    // check if this is a known Unicode whitespace character that
+                    // we can render using the space glyph with a custom width
+                    gfxFloat wid = mainFont->SynthesizeSpaceWidth(ch);
+                    if (wid >= 0.0) {
+                        nscoord advance =
+                            aTextRun->GetAppUnitsPerDevUnit() * floor(wid + 0.5);
+                        if (gfxShapedText::CompressedGlyph::IsSimpleAdvance(advance)) {
+                            aTextRun->GetCharacterGlyphs()[index].
+                                SetSimpleGlyph(advance,
+                                               mainFont->GetSpaceGlyph());
+                        } else {
+                            gfxTextRun::DetailedGlyph detailedGlyph;
+                            detailedGlyph.mGlyphID = mainFont->GetSpaceGlyph();
+                            detailedGlyph.mAdvance = advance;
+                            detailedGlyph.mXOffset = detailedGlyph.mYOffset = 0;
+                            gfxShapedText::CompressedGlyph g;
+                            g.SetComplex(true, true, 1);
+                            aTextRun->SetGlyphs(index,
+                                                g, &detailedGlyph);
+                        }
+                        continue;
+                    }
+                }
+
+                if (IsInvalidChar(ch)) {
+                    // invalid chars are left as zero-width/invisible
+                    continue;
+                }
+
+                // record char code so we can draw a box with the Unicode value
+                aTextRun->SetMissingGlyph(index, ch, mainFont);
+            }
+        }
+
+        runStart += matchedLength;
+    }
+}
+
+gfxTextRun *
+gfxFontGroup::GetEllipsisTextRun(int32_t aAppUnitsPerDevPixel,
+                                 LazyReferenceContextGetter& aRefContextGetter)
+{
+    if (mCachedEllipsisTextRun &&
+        mCachedEllipsisTextRun->GetAppUnitsPerDevUnit() == aAppUnitsPerDevPixel) {
+        return mCachedEllipsisTextRun;
+    }
+
+    // Use a Unicode ellipsis if the font supports it,
+    // otherwise use three ASCII periods as fallback.
+    gfxFont* firstFont = GetFontAt(0);
+    nsString ellipsis = firstFont->HasCharacter(kEllipsisChar[0])
+        ? nsDependentString(kEllipsisChar,
+                            ArrayLength(kEllipsisChar) - 1)
+        : nsDependentString(kASCIIPeriodsChar,
+                            ArrayLength(kASCIIPeriodsChar) - 1);
+
+    nsRefPtr<gfxContext> refCtx = aRefContextGetter.GetRefContext();
+    Parameters params = {
+        refCtx, nullptr, nullptr, nullptr, 0, aAppUnitsPerDevPixel
+    };
+    gfxTextRun* textRun =
+        MakeTextRun(ellipsis.get(), ellipsis.Length(), &params, TEXT_IS_PERSISTENT);
+    if (!textRun) {
+        return nullptr;
+    }
+    mCachedEllipsisTextRun = textRun;
+    textRun->ReleaseFontGroup(); // don't let the presence of a cached ellipsis
+                                 // textrun prolong the fontgroup's life
+    return textRun;
+}
+
+already_AddRefed<gfxFont>
+gfxFontGroup::TryAllFamilyMembers(gfxFontFamily* aFamily, uint32_t aCh)
+{
+    if (!aFamily->TestCharacterMap(aCh)) {
+        return nullptr;
+    }
+
+    // Note that we don't need the actual runScript in matchData for
+    // gfxFontFamily::SearchAllFontsForChar, it's only used for the
+    // system-fallback case. So we can just set it to 0 here.
+    GlobalFontMatch matchData(aCh, 0, &mStyle);
+    aFamily->SearchAllFontsForChar(&matchData);
+    gfxFontEntry *fe = matchData.mBestMatch;
+    if (!fe) {
+        return nullptr;
+    }
+
+    bool needsBold = mStyle.weight >= 600 && !fe->IsBold();
+    nsRefPtr<gfxFont> font = fe->FindOrMakeFont(&mStyle, needsBold);
+    return font.forget();
+}
+
+already_AddRefed<gfxFont>
+gfxFontGroup::FindFontForChar(uint32_t aCh, uint32_t aPrevCh,
+                              int32_t aRunScript, gfxFont *aPrevMatchedFont,
+                              uint8_t *aMatchType)
+{
+    // To optimize common cases, try the first font in the font-group
+    // before going into the more detailed checks below
+    uint32_t nextIndex = 0;
+    bool isJoinControl = gfxFontUtils::IsJoinControl(aCh);
+    bool wasJoinCauser = gfxFontUtils::IsJoinCauser(aPrevCh);
+    bool isVarSelector = gfxFontUtils::IsVarSelector(aCh);
+
+    if (!isJoinControl && !wasJoinCauser && !isVarSelector) {
+        nsRefPtr<gfxFont> firstFont = mFonts[0].Font();
+        if (firstFont->HasCharacter(aCh)) {
+            *aMatchType = gfxTextRange::kFontGroup;
+            return firstFont.forget();
+        }
+        // It's possible that another font in the family (e.g. regular face,
+        // where the requested style was italic) will support the character
+        nsRefPtr<gfxFont> font = TryAllFamilyMembers(mFonts[0].Family(), aCh);
+        if (font) {
+            *aMatchType = gfxTextRange::kFontGroup;
+            return font.forget();
+        }
+        // we don't need to check the first font again below
+        ++nextIndex;
+    }
+
+    if (aPrevMatchedFont) {
+        // Don't switch fonts for control characters, regardless of
+        // whether they are present in the current font, as they won't
+        // actually be rendered (see bug 716229)
+        if (isJoinControl ||
+            GetGeneralCategory(aCh) == HB_UNICODE_GENERAL_CATEGORY_CONTROL) {
+            nsRefPtr<gfxFont> ret = aPrevMatchedFont;
+            return ret.forget();
+        }
+
+        // if previous character was a join-causer (ZWJ),
+        // use the same font as the previous range if we can
+        if (wasJoinCauser) {
+            if (aPrevMatchedFont->HasCharacter(aCh)) {
+                nsRefPtr<gfxFont> ret = aPrevMatchedFont;
+                return ret.forget();
+            }
+        }
+    }
+
+    // if this character is a variation selector,
+    // use the previous font regardless of whether it supports VS or not.
+    // otherwise the text run will be divided.
+    if (isVarSelector) {
+        if (aPrevMatchedFont) {
+            nsRefPtr<gfxFont> ret = aPrevMatchedFont;
+            return ret.forget();
+        }
+        // VS alone. it's meaningless to search different fonts
+        return nullptr;
+    }
+
+    // 1. check remaining fonts in the font group
+    uint32_t fontListLength = FontListLength();
+    for (uint32_t i = nextIndex; i < fontListLength; i++) {
+        nsRefPtr<gfxFont> font = mFonts[i].Font();
+        if (font->HasCharacter(aCh)) {
+            *aMatchType = gfxTextRange::kFontGroup;
+            return font.forget();
+        }
+
+        font = TryAllFamilyMembers(mFonts[i].Family(), aCh);
+        if (font) {
+            *aMatchType = gfxTextRange::kFontGroup;
+            return font.forget();
+        }
+    }
+
+    // if character is in Private Use Area, don't do matching against pref or system fonts
+    if ((aCh >= 0xE000  && aCh <= 0xF8FF) || (aCh >= 0xF0000 && aCh <= 0x10FFFD))
+        return nullptr;
+
+    // 2. search pref fonts
+    nsRefPtr<gfxFont> font = WhichPrefFontSupportsChar(aCh);
+    if (font) {
+        *aMatchType = gfxTextRange::kPrefsFallback;
+        return font.forget();
+    }
+
+    // 3. use fallback fonts
+    // -- before searching for something else check the font used for the previous character
+    if (aPrevMatchedFont && aPrevMatchedFont->HasCharacter(aCh)) {
+        *aMatchType = gfxTextRange::kSystemFallback;
+        nsRefPtr<gfxFont> ret = aPrevMatchedFont;
+        return ret.forget();
+    }
+
+    // never fall back for characters from unknown scripts
+    if (aRunScript == HB_SCRIPT_UNKNOWN) {
+        return nullptr;
+    }
+
+    // for known "space" characters, don't do a full system-fallback search;
+    // we'll synthesize appropriate-width spaces instead of missing-glyph boxes
+    if (GetGeneralCategory(aCh) ==
+            HB_UNICODE_GENERAL_CATEGORY_SPACE_SEPARATOR &&
+        GetFontAt(0)->SynthesizeSpaceWidth(aCh) >= 0.0)
+    {
+        return nullptr;
+    }
+
+    // -- otherwise look for other stuff
+    *aMatchType = gfxTextRange::kSystemFallback;
+    font = WhichSystemFontSupportsChar(aCh, aRunScript);
+    return font.forget();
+}
+
+template<typename T>
+void gfxFontGroup::ComputeRanges(nsTArray<gfxTextRange>& aRanges,
+                                 const T *aString, uint32_t aLength,
+                                 int32_t aRunScript)
+{
+    NS_ASSERTION(aRanges.Length() == 0, "aRanges must be initially empty");
+    NS_ASSERTION(aLength > 0, "don't call ComputeRanges for zero-length text");
+
+    uint32_t prevCh = 0;
+    int32_t lastRangeIndex = -1;
+
+    // initialize prevFont to the group's primary font, so that this will be
+    // used for string-initial control chars, etc rather than risk hitting font
+    // fallback for these (bug 716229)
+    gfxFont *prevFont = GetFontAt(0);
+
+    // if we use the initial value of prevFont, we treat this as a match from
+    // the font group; fixes bug 978313
+    uint8_t matchType = gfxTextRange::kFontGroup;
+
+    for (uint32_t i = 0; i < aLength; i++) {
+
+        const uint32_t origI = i; // save off in case we increase for surrogate
+
+        // set up current ch
+        uint32_t ch = aString[i];
+
+        // in 16-bit case only, check for surrogate pair
+        if (sizeof(T) == sizeof(char16_t)) {
+            if ((i + 1 < aLength) && NS_IS_HIGH_SURROGATE(ch) &&
+                                 NS_IS_LOW_SURROGATE(aString[i + 1])) {
+                i++;
+                ch = SURROGATE_TO_UCS4(ch, aString[i]);
+            }
+        }
+
+        if (ch == 0xa0) {
+            ch = ' ';
+        }
+
+        // find the font for this char
+        nsRefPtr<gfxFont> font =
+            FindFontForChar(ch, prevCh, aRunScript, prevFont, &matchType);
+
+#ifndef RELEASE_BUILD
+        if (MOZ_UNLIKELY(mTextPerf)) {
+            if (matchType == gfxTextRange::kPrefsFallback) {
+                mTextPerf->current.fallbackPrefs++;
+            } else if (matchType == gfxTextRange::kSystemFallback) {
+                mTextPerf->current.fallbackSystem++;
+            }
+        }
+#endif
+
+        prevCh = ch;
+
+        if (lastRangeIndex == -1) {
+            // first char ==> make a new range
+            aRanges.AppendElement(gfxTextRange(0, 1, font, matchType));
+            lastRangeIndex++;
+            prevFont = font;
+        } else {
+            // if font has changed, make a new range
+            gfxTextRange& prevRange = aRanges[lastRangeIndex];
+            if (prevRange.font != font || prevRange.matchType != matchType) {
+                // close out the previous range
+                prevRange.end = origI;
+                aRanges.AppendElement(gfxTextRange(origI, i + 1,
+                                                   font, matchType));
+                lastRangeIndex++;
+
+                // update prevFont for the next match, *unless* we switched
+                // fonts on a ZWJ, in which case propagating the changed font
+                // is probably not a good idea (see bug 619511)
+                if (sizeof(T) == sizeof(uint8_t) ||
+                    !gfxFontUtils::IsJoinCauser(ch))
+                {
+                    prevFont = font;
+                }
+            }
+        }
+    }
+
+    aRanges[lastRangeIndex].end = aLength;
+}
+
+gfxUserFontSet* 
+gfxFontGroup::GetUserFontSet()
+{
+    return mUserFontSet;
+}
+
+void 
+gfxFontGroup::SetUserFontSet(gfxUserFontSet *aUserFontSet)
+{
+    if (aUserFontSet == mUserFontSet) {
+        return;
+    }
+    mUserFontSet = aUserFontSet;
+    mCurrGeneration = GetGeneration() - 1;
+    UpdateFontList();
+}
+
+uint64_t
+gfxFontGroup::GetGeneration()
+{
+    if (!mUserFontSet)
+        return 0;
+    return mUserFontSet->GetGeneration();
+}
+
+void
+gfxFontGroup::UpdateFontList()
+{
+    if (mCurrGeneration != GetGeneration()) {
+        // xxx - can probably improve this to detect when all fonts were found, so no need to update list
+        mFonts.Clear();
+        mUnderlineOffset = UNDERLINE_OFFSET_NOT_SET;
+        mSkipDrawing = false;
+
+        // bug 548184 - need to clean up FT2, OS/2 platform code to use BuildFontList
+#if defined(XP_MACOSX) || defined(XP_WIN) || defined(ANDROID)
+        BuildFontList();
+#else
+        ForEachFont(FindPlatformFont, this);
+#endif
+        mCurrGeneration = GetGeneration();
+        mCachedEllipsisTextRun = nullptr;
+    }
+}
+
+struct PrefFontCallbackData {
+    PrefFontCallbackData(nsTArray<nsRefPtr<gfxFontFamily> >& aFamiliesArray)
+        : mPrefFamilies(aFamiliesArray)
+    {}
+
+    nsTArray<nsRefPtr<gfxFontFamily> >& mPrefFamilies;
+
+    static bool AddFontFamilyEntry(eFontPrefLang aLang, const nsAString& aName, void *aClosure)
+    {
+        PrefFontCallbackData *prefFontData = static_cast<PrefFontCallbackData*>(aClosure);
+
+        gfxFontFamily *family = gfxPlatformFontList::PlatformFontList()->FindFamily(aName);
+        if (family) {
+            prefFontData->mPrefFamilies.AppendElement(family);
+        }
+        return true;
+    }
+};
+
+already_AddRefed<gfxFont>
+gfxFontGroup::WhichPrefFontSupportsChar(uint32_t aCh)
+{
+    nsRefPtr<gfxFont> font;
+
+    // get the pref font list if it hasn't been set up already
+    uint32_t unicodeRange = FindCharUnicodeRange(aCh);
+    eFontPrefLang charLang = gfxPlatform::GetPlatform()->GetFontPrefLangFor(unicodeRange);
+
+    // if the last pref font was the first family in the pref list, no need to recheck through a list of families
+    if (mLastPrefFont && charLang == mLastPrefLang &&
+        mLastPrefFirstFont && mLastPrefFont->HasCharacter(aCh)) {
+        font = mLastPrefFont;
+        return font.forget();
+    }
+
+    // based on char lang and page lang, set up list of pref lang fonts to check
+    eFontPrefLang prefLangs[kMaxLenPrefLangList];
+    uint32_t i, numLangs = 0;
+
+    gfxPlatform::GetPlatform()->GetLangPrefs(prefLangs, numLangs, charLang, mPageLang);
+
+    for (i = 0; i < numLangs; i++) {
+        nsAutoTArray<nsRefPtr<gfxFontFamily>, 5> families;
+        eFontPrefLang currentLang = prefLangs[i];
+
+        gfxPlatformFontList *fontList = gfxPlatformFontList::PlatformFontList();
+
+        // get the pref families for a single pref lang
+        if (!fontList->GetPrefFontFamilyEntries(currentLang, &families)) {
+            eFontPrefLang prefLangsToSearch[1] = { currentLang };
+            PrefFontCallbackData prefFontData(families);
+            gfxPlatform::ForEachPrefFont(prefLangsToSearch, 1, PrefFontCallbackData::AddFontFamilyEntry,
+                                           &prefFontData);
+            fontList->SetPrefFontFamilyEntries(currentLang, families);
+        }
+
+        // find the first pref font that includes the character
+        uint32_t  j, numPrefs;
+        numPrefs = families.Length();
+        for (j = 0; j < numPrefs; j++) {
+            // look up the appropriate face
+            gfxFontFamily *family = families[j];
+            if (!family) continue;
+
+            // if a pref font is used, it's likely to be used again in the same text run.
+            // the style doesn't change so the face lookup can be cached rather than calling
+            // FindOrMakeFont repeatedly.  speeds up FindFontForChar lookup times for subsequent
+            // pref font lookups
+            if (family == mLastPrefFamily && mLastPrefFont->HasCharacter(aCh)) {
+                font = mLastPrefFont;
+                return font.forget();
+            }
+
+            bool needsBold;
+            gfxFontEntry *fe = family->FindFontForStyle(mStyle, needsBold);
+            // if ch in cmap, create and return a gfxFont
+            if (fe && fe->TestCharacterMap(aCh)) {
+                nsRefPtr<gfxFont> prefFont = fe->FindOrMakeFont(&mStyle, needsBold);
+                if (!prefFont) continue;
+                mLastPrefFamily = family;
+                mLastPrefFont = prefFont;
+                mLastPrefLang = charLang;
+                mLastPrefFirstFont = (i == 0 && j == 0);
+                return prefFont.forget();
+            }
+
+        }
+    }
+
+    return nullptr;
+}
+
+already_AddRefed<gfxFont>
+gfxFontGroup::WhichSystemFontSupportsChar(uint32_t aCh, int32_t aRunScript)
+{
+    gfxFontEntry *fe = 
+        gfxPlatformFontList::PlatformFontList()->
+            SystemFindFontForChar(aCh, aRunScript, &mStyle);
+    if (fe) {
+        bool wantBold = mStyle.ComputeWeight() >= 6;
+        nsRefPtr<gfxFont> font =
+            fe->FindOrMakeFont(&mStyle, wantBold && !fe->IsBold());
+        return font.forget();
+    }
+
+    return nullptr;
+}
+
+/*static*/ void
+gfxFontGroup::Shutdown()
+{
+    NS_IF_RELEASE(gLangService);
+}
+
+nsILanguageAtomService* gfxFontGroup::gLangService = nullptr;
+
+
+#define DEFAULT_PIXEL_FONT_SIZE 16.0f
+
+/*static*/ uint32_t
+gfxFontStyle::ParseFontLanguageOverride(const nsString& aLangTag)
+{
+  if (!aLangTag.Length() || aLangTag.Length() > 4) {
+    return NO_FONT_LANGUAGE_OVERRIDE;
+  }
+  uint32_t index, result = 0;
+  for (index = 0; index < aLangTag.Length(); ++index) {
+    char16_t ch = aLangTag[index];
+    if (!nsCRT::IsAscii(ch)) { // valid tags are pure ASCII
+      return NO_FONT_LANGUAGE_OVERRIDE;
+    }
+    result = (result << 8) + ch;
+  }
+  while (index++ < 4) {
+    result = (result << 8) + 0x20;
+  }
+  return result;
+}
+
+gfxFontStyle::gfxFontStyle() :
+    language(nsGkAtoms::x_western),
+    size(DEFAULT_PIXEL_FONT_SIZE), sizeAdjust(0.0f),
+    languageOverride(NO_FONT_LANGUAGE_OVERRIDE),
+    weight(NS_FONT_WEIGHT_NORMAL), stretch(NS_FONT_STRETCH_NORMAL),
+    systemFont(true), printerFont(false), useGrayscaleAntialiasing(false),
+    style(NS_FONT_STYLE_NORMAL)
+{
+}
+
+gfxFontStyle::gfxFontStyle(uint8_t aStyle, uint16_t aWeight, int16_t aStretch,
+                           gfxFloat aSize, nsIAtom *aLanguage,
+                           float aSizeAdjust, bool aSystemFont,
+                           bool aPrinterFont,
+                           const nsString& aLanguageOverride):
+    language(aLanguage),
+    size(aSize), sizeAdjust(aSizeAdjust),
+    languageOverride(ParseFontLanguageOverride(aLanguageOverride)),
+    weight(aWeight), stretch(aStretch),
+    systemFont(aSystemFont), printerFont(aPrinterFont),
+    useGrayscaleAntialiasing(false), style(aStyle)
+{
+    MOZ_ASSERT(!mozilla::IsNaN(size));
+    MOZ_ASSERT(!mozilla::IsNaN(sizeAdjust));
+
+    if (weight > 900)
+        weight = 900;
+    if (weight < 100)
+        weight = 100;
+
+    if (size >= FONT_MAX_SIZE) {
+        size = FONT_MAX_SIZE;
+        sizeAdjust = 0.0;
+    } else if (size < 0.0) {
+        NS_WARNING("negative font size");
+        size = 0.0;
+    }
+
+    if (!language) {
+        NS_WARNING("null language");
+        language = nsGkAtoms::x_western;
+    }
+}
+
+gfxFontStyle::gfxFontStyle(const gfxFontStyle& aStyle) :
+    language(aStyle.language),
+    featureValueLookup(aStyle.featureValueLookup),
+    size(aStyle.size), sizeAdjust(aStyle.sizeAdjust),
+    languageOverride(aStyle.languageOverride),
+    weight(aStyle.weight), stretch(aStyle.stretch),
+    systemFont(aStyle.systemFont), printerFont(aStyle.printerFont),
+    useGrayscaleAntialiasing(aStyle.useGrayscaleAntialiasing),
+    style(aStyle.style)
+{
+    featureSettings.AppendElements(aStyle.featureSettings);
+    alternateValues.AppendElements(aStyle.alternateValues);
+}
+
+int8_t
+gfxFontStyle::ComputeWeight() const
+{
+    int8_t baseWeight = (weight + 50) / 100;
+
+    if (baseWeight < 0)
+        baseWeight = 0;
+    if (baseWeight > 9)
+        baseWeight = 9;
+
+    return baseWeight;
+}
+
+void
+gfxShapedText::SetupClusterBoundaries(uint32_t         aOffset,
+                                      const char16_t *aString,
+                                      uint32_t         aLength)
+{
+    CompressedGlyph *glyphs = GetCharacterGlyphs() + aOffset;
+
+    gfxTextRun::CompressedGlyph extendCluster;
+    extendCluster.SetComplex(false, true, 0);
+
+    ClusterIterator iter(aString, aLength);
+
+    // the ClusterIterator won't be able to tell us if the string
+    // _begins_ with a cluster-extender, so we handle that here
+    if (aLength && IsClusterExtender(*aString)) {
+        *glyphs = extendCluster;
+    }
+
+    while (!iter.AtEnd()) {
+        if (*iter == char16_t(' ')) {
+            glyphs->SetIsSpace();
+        }
+        // advance iter to the next cluster-start (or end of text)
+        iter.Next();
+        // step past the first char of the cluster
+        aString++;
+        glyphs++;
+        // mark all the rest as cluster-continuations
+        while (aString < iter) {
+            *glyphs = extendCluster;
+            if (NS_IS_LOW_SURROGATE(*aString)) {
+                glyphs->SetIsLowSurrogate();
+            }
+            glyphs++;
+            aString++;
+        }
+    }
+}
+
+void
+gfxShapedText::SetupClusterBoundaries(uint32_t       aOffset,
+                                      const uint8_t *aString,
+                                      uint32_t       aLength)
+{
+    CompressedGlyph *glyphs = GetCharacterGlyphs() + aOffset;
+    const uint8_t *limit = aString + aLength;
+
+    while (aString < limit) {
+        if (*aString == uint8_t(' ')) {
+            glyphs->SetIsSpace();
+        }
+        aString++;
+        glyphs++;
+    }
+}
+
+gfxShapedText::DetailedGlyph *
+gfxShapedText::AllocateDetailedGlyphs(uint32_t aIndex, uint32_t aCount)
+{
+    NS_ASSERTION(aIndex < GetLength(), "Index out of range");
+
+    if (!mDetailedGlyphs) {
+        mDetailedGlyphs = new DetailedGlyphStore();
+    }
+
+    DetailedGlyph *details = mDetailedGlyphs->Allocate(aIndex, aCount);
+    if (!details) {
+        GetCharacterGlyphs()[aIndex].SetMissing(0);
+        return nullptr;
+    }
+
+    return details;
+}
+
+void
+gfxShapedText::SetGlyphs(uint32_t aIndex, CompressedGlyph aGlyph,
+                         const DetailedGlyph *aGlyphs)
+{
+    NS_ASSERTION(!aGlyph.IsSimpleGlyph(), "Simple glyphs not handled here");
+    NS_ASSERTION(aIndex > 0 || aGlyph.IsLigatureGroupStart(),
+                 "First character can't be a ligature continuation!");
+
+    uint32_t glyphCount = aGlyph.GetGlyphCount();
+    if (glyphCount > 0) {
+        DetailedGlyph *details = AllocateDetailedGlyphs(aIndex, glyphCount);
+        if (!details) {
+            return;
+        }
+        memcpy(details, aGlyphs, sizeof(DetailedGlyph)*glyphCount);
+    }
+    GetCharacterGlyphs()[aIndex] = aGlyph;
+}
+
+#define ZWNJ 0x200C
+#define ZWJ  0x200D
+// U+061C ARABIC LETTER MARK is expected to be added to XIDMOD_DEFAULT_IGNORABLE
+// in a future Unicode update. Add it manually for now
+#define ALM  0x061C
+static inline bool
+IsDefaultIgnorable(uint32_t aChar)
+{
+    return GetIdentifierModification(aChar) == XIDMOD_DEFAULT_IGNORABLE ||
+           aChar == ZWNJ || aChar == ZWJ || aChar == ALM;
+}
+
+void
+gfxShapedText::SetMissingGlyph(uint32_t aIndex, uint32_t aChar, gfxFont *aFont)
+{
+    uint8_t category = GetGeneralCategory(aChar);
+    if (category >= HB_UNICODE_GENERAL_CATEGORY_SPACING_MARK &&
+        category <= HB_UNICODE_GENERAL_CATEGORY_NON_SPACING_MARK)
+    {
+        GetCharacterGlyphs()[aIndex].SetComplex(false, true, 0);
+    }
+
+    DetailedGlyph *details = AllocateDetailedGlyphs(aIndex, 1);
+    if (!details) {
+        return;
+    }
+
+    details->mGlyphID = aChar;
+    if (IsDefaultIgnorable(aChar)) {
+        // Setting advance width to zero will prevent drawing the hexbox
+        details->mAdvance = 0;
+    } else {
+        gfxFloat width =
+            std::max(aFont->GetMetrics().aveCharWidth,
+                     gfxFontMissingGlyphs::GetDesiredMinWidth(aChar,
+                         mAppUnitsPerDevUnit));
+        details->mAdvance = uint32_t(width * mAppUnitsPerDevUnit);
+    }
+    details->mXOffset = 0;
+    details->mYOffset = 0;
+    GetCharacterGlyphs()[aIndex].SetMissing(1);
+}
+
+bool
+gfxShapedText::FilterIfIgnorable(uint32_t aIndex, uint32_t aCh)
+{
+    if (IsDefaultIgnorable(aCh)) {
+        DetailedGlyph *details = AllocateDetailedGlyphs(aIndex, 1);
+        if (details) {
+            details->mGlyphID = aCh;
+            details->mAdvance = 0;
+            details->mXOffset = 0;
+            details->mYOffset = 0;
+            GetCharacterGlyphs()[aIndex].SetMissing(1);
+            return true;
+        }
+    }
+    return false;
+}
+
+void
+gfxShapedText::AdjustAdvancesForSyntheticBold(float aSynBoldOffset,
+                                              uint32_t aOffset,
+                                              uint32_t aLength)
+{
+    uint32_t synAppUnitOffset = aSynBoldOffset * mAppUnitsPerDevUnit;
+    CompressedGlyph *charGlyphs = GetCharacterGlyphs();
+    for (uint32_t i = aOffset; i < aOffset + aLength; ++i) {
+         CompressedGlyph *glyphData = charGlyphs + i;
+         if (glyphData->IsSimpleGlyph()) {
+             // simple glyphs ==> just add the advance
+             int32_t advance = glyphData->GetSimpleAdvance() + synAppUnitOffset;
+             if (CompressedGlyph::IsSimpleAdvance(advance)) {
+                 glyphData->SetSimpleGlyph(advance, glyphData->GetSimpleGlyph());
+             } else {
+                 // rare case, tested by making this the default
+                 uint32_t glyphIndex = glyphData->GetSimpleGlyph();
+                 glyphData->SetComplex(true, true, 1);
+                 DetailedGlyph detail = {glyphIndex, advance, 0, 0};
+                 SetGlyphs(i, *glyphData, &detail);
+             }
+         } else {
+             // complex glyphs ==> add offset at cluster/ligature boundaries
+             uint32_t detailedLength = glyphData->GetGlyphCount();
+             if (detailedLength) {
+                 DetailedGlyph *details = GetDetailedGlyphs(i);
+                 if (!details) {
+                     continue;
+                 }
+                 if (IsRightToLeft()) {
+                     details[0].mAdvance += synAppUnitOffset;
+                 } else {
+                     details[detailedLength - 1].mAdvance += synAppUnitOffset;
+                 }
+             }
+         }
+    }
+}
+
+bool
+gfxTextRun::GlyphRunIterator::NextRun()  {
+    if (mNextIndex >= mTextRun->mGlyphRuns.Length())
+        return false;
+    mGlyphRun = &mTextRun->mGlyphRuns[mNextIndex];
+    if (mGlyphRun->mCharacterOffset >= mEndOffset)
+        return false;
+
+    mStringStart = std::max(mStartOffset, mGlyphRun->mCharacterOffset);
+    uint32_t last = mNextIndex + 1 < mTextRun->mGlyphRuns.Length()
+        ? mTextRun->mGlyphRuns[mNextIndex + 1].mCharacterOffset : mTextRun->GetLength();
+    mStringEnd = std::min(mEndOffset, last);
+
+    ++mNextIndex;
+    return true;
+}
+
+#ifdef DEBUG_TEXT_RUN_STORAGE_METRICS
+static void
+AccountStorageForTextRun(gfxTextRun *aTextRun, int32_t aSign)
+{
+    // Ignores detailed glyphs... we don't know when those have been constructed
+    // Also ignores gfxSkipChars dynamic storage (which won't be anything
+    // for preformatted text)
+    // Also ignores GlyphRun array, again because it hasn't been constructed
+    // by the time this gets called. If there's only one glyphrun that's stored
+    // directly in the textrun anyway so no additional overhead.
+    uint32_t length = aTextRun->GetLength();
+    int32_t bytes = length * sizeof(gfxTextRun::CompressedGlyph);
+    bytes += sizeof(gfxTextRun);
+    gTextRunStorage += bytes*aSign;
+    gTextRunStorageHighWaterMark = std::max(gTextRunStorageHighWaterMark, gTextRunStorage);
+}
+#endif
+
+// Helper for textRun creation to preallocate storage for glyph records;
+// this function returns a pointer to the newly-allocated glyph storage.
+// Returns nullptr if allocation fails.
+void *
+gfxTextRun::AllocateStorageForTextRun(size_t aSize, uint32_t aLength)
+{
+    // Allocate the storage we need, returning nullptr on failure rather than
+    // throwing an exception (because web content can create huge runs).
+    void *storage = moz_malloc(aSize + aLength * sizeof(CompressedGlyph));
+    if (!storage) {
+        NS_WARNING("failed to allocate storage for text run!");
+        return nullptr;
+    }
+
+    // Initialize the glyph storage (beyond aSize) to zero
+    memset(reinterpret_cast<char*>(storage) + aSize, 0,
+           aLength * sizeof(CompressedGlyph));
+
+    return storage;
+}
+
+gfxTextRun *
+gfxTextRun::Create(const gfxTextRunFactory::Parameters *aParams,
+                   uint32_t aLength, gfxFontGroup *aFontGroup, uint32_t aFlags)
+{
+    void *storage = AllocateStorageForTextRun(sizeof(gfxTextRun), aLength);
+    if (!storage) {
+        return nullptr;
+    }
+
+    return new (storage) gfxTextRun(aParams, aLength, aFontGroup, aFlags);
+}
+
+gfxTextRun::gfxTextRun(const gfxTextRunFactory::Parameters *aParams,
+                       uint32_t aLength, gfxFontGroup *aFontGroup, uint32_t aFlags)
+    : gfxShapedText(aLength, aFlags, aParams->mAppUnitsPerDevUnit)
+    , mUserData(aParams->mUserData)
+    , mFontGroup(aFontGroup)
+    , mReleasedFontGroup(false)
+{
+    NS_ASSERTION(mAppUnitsPerDevUnit > 0, "Invalid app unit scale");
+    MOZ_COUNT_CTOR(gfxTextRun);
+    NS_ADDREF(mFontGroup);
+
+#ifndef RELEASE_BUILD
+    gfxTextPerfMetrics *tp = aFontGroup->GetTextPerfMetrics();
+    if (tp) {
+        tp->current.textrunConst++;
+    }
+#endif
+
+    mCharacterGlyphs = reinterpret_cast<CompressedGlyph*>(this + 1);
+
+    if (aParams->mSkipChars) {
+        mSkipChars.TakeFrom(aParams->mSkipChars);
+    }
+
+#ifdef DEBUG_TEXT_RUN_STORAGE_METRICS
+    AccountStorageForTextRun(this, 1);
+#endif
+
+    mSkipDrawing = mFontGroup->ShouldSkipDrawing();
+}
+
+gfxTextRun::~gfxTextRun()
+{
+#ifdef DEBUG_TEXT_RUN_STORAGE_METRICS
+    AccountStorageForTextRun(this, -1);
+#endif
+#ifdef DEBUG
+    // Make it easy to detect a dead text run
+    mFlags = 0xFFFFFFFF;
+#endif
+
+    // The cached ellipsis textrun (if any) in a fontgroup will have already
+    // been told to release its reference to the group, so we mustn't do that
+    // again here.
+    if (!mReleasedFontGroup) {
+#ifndef RELEASE_BUILD
+        gfxTextPerfMetrics *tp = mFontGroup->GetTextPerfMetrics();
+        if (tp) {
+            tp->current.textrunDestr++;
+        }
+#endif
+        NS_RELEASE(mFontGroup);
+    }
+
+    MOZ_COUNT_DTOR(gfxTextRun);
+}
+
+void
+gfxTextRun::ReleaseFontGroup()
+{
+    NS_ASSERTION(!mReleasedFontGroup, "doubly released!");
+    NS_RELEASE(mFontGroup);
+    mReleasedFontGroup = true;
+}
+
+bool
+gfxTextRun::SetPotentialLineBreaks(uint32_t aStart, uint32_t aLength,
+                                   uint8_t *aBreakBefore,
+                                   gfxContext *aRefContext)
+{
+    NS_ASSERTION(aStart + aLength <= GetLength(), "Overflow");
+
+    uint32_t changed = 0;
+    uint32_t i;
+    CompressedGlyph *charGlyphs = mCharacterGlyphs + aStart;
+    for (i = 0; i < aLength; ++i) {
+        uint8_t canBreak = aBreakBefore[i];
+        if (canBreak && !charGlyphs[i].IsClusterStart()) {
+            // This can happen ... there is no guarantee that our linebreaking rules
+            // align with the platform's idea of what constitutes a cluster.
+            NS_WARNING("Break suggested inside cluster!");
+            canBreak = CompressedGlyph::FLAG_BREAK_TYPE_NONE;
+        }
+        changed |= charGlyphs[i].SetCanBreakBefore(canBreak);
+    }
+    return changed != 0;
+}
+
+gfxTextRun::LigatureData
+gfxTextRun::ComputeLigatureData(uint32_t aPartStart, uint32_t aPartEnd,
+                                PropertyProvider *aProvider)
+{
+    NS_ASSERTION(aPartStart < aPartEnd, "Computing ligature data for empty range");
+    NS_ASSERTION(aPartEnd <= GetLength(), "Character length overflow");
+  
+    LigatureData result;
+    CompressedGlyph *charGlyphs = mCharacterGlyphs;
+
+    uint32_t i;
+    for (i = aPartStart; !charGlyphs[i].IsLigatureGroupStart(); --i) {
+        NS_ASSERTION(i > 0, "Ligature at the start of the run??");
+    }
+    result.mLigatureStart = i;
+    for (i = aPartStart + 1; i < GetLength() && !charGlyphs[i].IsLigatureGroupStart(); ++i) {
+    }
+    result.mLigatureEnd = i;
+
+    int32_t ligatureWidth =
+        GetAdvanceForGlyphs(result.mLigatureStart, result.mLigatureEnd);
+    // Count the number of started clusters we have seen
+    uint32_t totalClusterCount = 0;
+    uint32_t partClusterIndex = 0;
+    uint32_t partClusterCount = 0;
+    for (i = result.mLigatureStart; i < result.mLigatureEnd; ++i) {
+        // Treat the first character of the ligature as the start of a
+        // cluster for our purposes of allocating ligature width to its
+        // characters.
+        if (i == result.mLigatureStart || charGlyphs[i].IsClusterStart()) {
+            ++totalClusterCount;
+            if (i < aPartStart) {
+                ++partClusterIndex;
+            } else if (i < aPartEnd) {
+                ++partClusterCount;
+            }
+        }
+    }
+    NS_ASSERTION(totalClusterCount > 0, "Ligature involving no clusters??");
+    result.mPartAdvance = partClusterIndex * (ligatureWidth / totalClusterCount);
+    result.mPartWidth = partClusterCount * (ligatureWidth / totalClusterCount);
+
+    // Any rounding errors are apportioned to the final part of the ligature,
+    // so that measuring all parts of a ligature and summing them is equal to
+    // the ligature width.
+    if (aPartEnd == result.mLigatureEnd) {
+        gfxFloat allParts = totalClusterCount * (ligatureWidth / totalClusterCount);
+        result.mPartWidth += ligatureWidth - allParts;
+    }
+
+    if (partClusterCount == 0) {
+        // nothing to draw
+        result.mClipBeforePart = result.mClipAfterPart = true;
+    } else {
+        // Determine whether we should clip before or after this part when
+        // drawing its slice of the ligature.
+        // We need to clip before the part if any cluster is drawn before
+        // this part.
+        result.mClipBeforePart = partClusterIndex > 0;
+        // We need to clip after the part if any cluster is drawn after
+        // this part.
+        result.mClipAfterPart = partClusterIndex + partClusterCount < totalClusterCount;
+    }
+
+    if (aProvider && (mFlags & gfxTextRunFactory::TEXT_ENABLE_SPACING)) {
+        gfxFont::Spacing spacing;
+        if (aPartStart == result.mLigatureStart) {
+            aProvider->GetSpacing(aPartStart, 1, &spacing);
+            result.mPartWidth += spacing.mBefore;
+        }
+        if (aPartEnd == result.mLigatureEnd) {
+            aProvider->GetSpacing(aPartEnd - 1, 1, &spacing);
+            result.mPartWidth += spacing.mAfter;
+        }
+    }
+
+    return result;
+}
+
+gfxFloat
+gfxTextRun::ComputePartialLigatureWidth(uint32_t aPartStart, uint32_t aPartEnd,
+                                        PropertyProvider *aProvider)
+{
+    if (aPartStart >= aPartEnd)
+        return 0;
+    LigatureData data = ComputeLigatureData(aPartStart, aPartEnd, aProvider);
+    return data.mPartWidth;
+}
+
+int32_t
+gfxTextRun::GetAdvanceForGlyphs(uint32_t aStart, uint32_t aEnd)
+{
+    const CompressedGlyph *glyphData = mCharacterGlyphs + aStart;
+    int32_t advance = 0;
+    uint32_t i;
+    for (i = aStart; i < aEnd; ++i, ++glyphData) {
+        if (glyphData->IsSimpleGlyph()) {
+            advance += glyphData->GetSimpleAdvance();   
+        } else {
+            uint32_t glyphCount = glyphData->GetGlyphCount();
+            if (glyphCount == 0) {
+                continue;
+            }
+            const DetailedGlyph *details = GetDetailedGlyphs(i);
+            if (details) {
+                uint32_t j;
+                for (j = 0; j < glyphCount; ++j, ++details) {
+                    advance += details->mAdvance;
+                }
+            }
+        }
+    }
+    return advance;
+}
+
+static void
+GetAdjustedSpacing(gfxTextRun *aTextRun, uint32_t aStart, uint32_t aEnd,
+                   gfxTextRun::PropertyProvider *aProvider,
+                   gfxTextRun::PropertyProvider::Spacing *aSpacing)
+{
+    if (aStart >= aEnd)
+        return;
+
+    aProvider->GetSpacing(aStart, aEnd - aStart, aSpacing);
+
+#ifdef DEBUG
+    // Check to see if we have spacing inside ligatures
+
+    const gfxTextRun::CompressedGlyph *charGlyphs = aTextRun->GetCharacterGlyphs();
+    uint32_t i;
+
+    for (i = aStart; i < aEnd; ++i) {
+        if (!charGlyphs[i].IsLigatureGroupStart()) {
+            NS_ASSERTION(i == aStart || aSpacing[i - aStart].mBefore == 0,
+                         "Before-spacing inside a ligature!");
+            NS_ASSERTION(i - 1 <= aStart || aSpacing[i - 1 - aStart].mAfter == 0,
+                         "After-spacing inside a ligature!");
+        }
+    }
+#endif
+}
+
+bool
+gfxTextRun::GetAdjustedSpacingArray(uint32_t aStart, uint32_t aEnd,
+                                    PropertyProvider *aProvider,
+                                    uint32_t aSpacingStart, uint32_t aSpacingEnd,
+                                    nsTArray<PropertyProvider::Spacing> *aSpacing)
+{
+    if (!aProvider || !(mFlags & gfxTextRunFactory::TEXT_ENABLE_SPACING))
+        return false;
+    if (!aSpacing->AppendElements(aEnd - aStart))
+        return false;
+    memset(aSpacing->Elements(), 0, sizeof(gfxFont::Spacing)*(aSpacingStart - aStart));
+    GetAdjustedSpacing(this, aSpacingStart, aSpacingEnd, aProvider,
+                       aSpacing->Elements() + aSpacingStart - aStart);
+    memset(aSpacing->Elements() + aSpacingEnd - aStart, 0, sizeof(gfxFont::Spacing)*(aEnd - aSpacingEnd));
+    return true;
+}
+
+void
+gfxTextRun::ShrinkToLigatureBoundaries(uint32_t *aStart, uint32_t *aEnd)
+{
+    if (*aStart >= *aEnd)
+        return;
+  
+    CompressedGlyph *charGlyphs = mCharacterGlyphs;
+
+    while (*aStart < *aEnd && !charGlyphs[*aStart].IsLigatureGroupStart()) {
+        ++(*aStart);
+    }
+    if (*aEnd < GetLength()) {
+        while (*aEnd > *aStart && !charGlyphs[*aEnd].IsLigatureGroupStart()) {
+            --(*aEnd);
+        }
+    }
+}
+
+void
+gfxTextRun::DrawGlyphs(gfxFont *aFont, gfxContext *aContext,
+                       DrawMode aDrawMode, gfxPoint *aPt,
+                       gfxTextContextPaint *aContextPaint,
+                       uint32_t aStart, uint32_t aEnd,
+                       PropertyProvider *aProvider,
+                       uint32_t aSpacingStart, uint32_t aSpacingEnd,
+                       gfxTextRunDrawCallbacks *aCallbacks)
+{
+    nsAutoTArray<PropertyProvider::Spacing,200> spacingBuffer;
+    bool haveSpacing = GetAdjustedSpacingArray(aStart, aEnd, aProvider,
+        aSpacingStart, aSpacingEnd, &spacingBuffer);
+    aFont->Draw(this, aStart, aEnd, aContext, aDrawMode, aPt,
+                haveSpacing ? spacingBuffer.Elements() : nullptr, aContextPaint,
+                aCallbacks);
+}
+
+static void
+ClipPartialLigature(gfxTextRun *aTextRun, gfxFloat *aLeft, gfxFloat *aRight,
+                    gfxFloat aXOrigin, gfxTextRun::LigatureData *aLigature)
+{
+    if (aLigature->mClipBeforePart) {
+        if (aTextRun->IsRightToLeft()) {
+            *aRight = std::min(*aRight, aXOrigin);
+        } else {
+            *aLeft = std::max(*aLeft, aXOrigin);
+        }
+    }
+    if (aLigature->mClipAfterPart) {
+        gfxFloat endEdge = aXOrigin + aTextRun->GetDirection()*aLigature->mPartWidth;
+        if (aTextRun->IsRightToLeft()) {
+            *aLeft = std::max(*aLeft, endEdge);
+        } else {
+            *aRight = std::min(*aRight, endEdge);
+        }
+    }    
+}
+
+void
+gfxTextRun::DrawPartialLigature(gfxFont *aFont, gfxContext *aCtx,
+                                uint32_t aStart, uint32_t aEnd,
+                                gfxPoint *aPt,
+                                PropertyProvider *aProvider,
+                                gfxTextRunDrawCallbacks *aCallbacks)
+{
+    if (aStart >= aEnd)
+        return;
+
+    // Draw partial ligature. We hack this by clipping the ligature.
+    LigatureData data = ComputeLigatureData(aStart, aEnd, aProvider);
+    gfxRect clipExtents = aCtx->GetClipExtents();
+    gfxFloat left = clipExtents.X()*mAppUnitsPerDevUnit;
+    gfxFloat right = clipExtents.XMost()*mAppUnitsPerDevUnit;
+    ClipPartialLigature(this, &left, &right, aPt->x, &data);
+
+    {
+      // Need to preserve the path, otherwise this can break canvas text-on-path;
+      // in general it seems like a good thing, as naive callers probably won't
+      // expect gfxTextRun::Draw to implicitly destroy the current path.
+      gfxContextPathAutoSaveRestore savePath(aCtx);
+
+      // use division here to ensure that when the rect is aligned on multiples
+      // of mAppUnitsPerDevUnit, we clip to true device unit boundaries.
+      // Also, make sure we snap the rectangle to device pixels.
+      aCtx->Save();
+      aCtx->NewPath();
+      aCtx->Rectangle(gfxRect(left / mAppUnitsPerDevUnit,
+                              clipExtents.Y(),
+                              (right - left) / mAppUnitsPerDevUnit,
+                              clipExtents.Height()), true);
+      aCtx->Clip();
+    }
+
+    gfxFloat direction = GetDirection();
+    gfxPoint pt(aPt->x - direction*data.mPartAdvance, aPt->y);
+    DrawGlyphs(aFont, aCtx,
+               aCallbacks ? DrawMode::GLYPH_PATH : DrawMode::GLYPH_FILL, &pt,
+               nullptr, data.mLigatureStart, data.mLigatureEnd, aProvider,
+               aStart, aEnd, aCallbacks);
+    aCtx->Restore();
+
+    aPt->x += direction*data.mPartWidth;
+}
+
+// returns true if a glyph run is using a font with synthetic bolding enabled, false otherwise
+static bool
+HasSyntheticBold(gfxTextRun *aRun, uint32_t aStart, uint32_t aLength)
+{
+    gfxTextRun::GlyphRunIterator iter(aRun, aStart, aLength);
+    while (iter.NextRun()) {
+        gfxFont *font = iter.GetGlyphRun()->mFont;
+        if (font && font->IsSyntheticBold()) {
+            return true;
+        }
+    }
+
+    return false;
+}
+
+// returns true if color is non-opaque (i.e. alpha != 1.0) or completely transparent, false otherwise
+// if true, color is set on output
+static bool
+HasNonOpaqueColor(gfxContext *aContext, gfxRGBA& aCurrentColor)
+{
+    if (aContext->GetDeviceColor(aCurrentColor)) {
+        if (aCurrentColor.a < 1.0 && aCurrentColor.a > 0.0) {
+            return true;
+        }
+    }
+        
+    return false;
+}
+
+// helper class for double-buffering drawing with non-opaque color
+struct BufferAlphaColor {
+    BufferAlphaColor(gfxContext *aContext)
+        : mContext(aContext)
+    {
+
+    }
+
+    ~BufferAlphaColor() {}
+
+    void PushSolidColor(const gfxRect& aBounds, const gfxRGBA& aAlphaColor, uint32_t appsPerDevUnit)
+    {
+        mContext->Save();
+        mContext->NewPath();
+        mContext->Rectangle(gfxRect(aBounds.X() / appsPerDevUnit,
+                    aBounds.Y() / appsPerDevUnit,
+                    aBounds.Width() / appsPerDevUnit,
+                    aBounds.Height() / appsPerDevUnit), true);
+        mContext->Clip();
+        mContext->SetColor(gfxRGBA(aAlphaColor.r, aAlphaColor.g, aAlphaColor.b));
+        mContext->PushGroup(gfxContentType::COLOR_ALPHA);
+        mAlpha = aAlphaColor.a;
+    }
+
+    void PopAlpha()
+    {
+        // pop the text, using the color alpha as the opacity
+        mContext->PopGroupToSource();
+        mContext->SetOperator(gfxContext::OPERATOR_OVER);
+        mContext->Paint(mAlpha);
+        mContext->Restore();
+    }
+
+    gfxContext *mContext;
+    gfxFloat mAlpha;
+};
+
+void
+gfxTextRun::Draw(gfxContext *aContext, gfxPoint aPt, DrawMode aDrawMode,
+                 uint32_t aStart, uint32_t aLength,
+                 PropertyProvider *aProvider, gfxFloat *aAdvanceWidth,
+                 gfxTextContextPaint *aContextPaint,
+                 gfxTextRunDrawCallbacks *aCallbacks)
+{
+    NS_ASSERTION(aStart + aLength <= GetLength(), "Substring out of range");
+    NS_ASSERTION(aDrawMode == DrawMode::GLYPH_PATH || !(int(aDrawMode) & int(DrawMode::GLYPH_PATH)),
+                 "GLYPH_PATH cannot be used with GLYPH_FILL, GLYPH_STROKE or GLYPH_STROKE_UNDERNEATH");
+    NS_ASSERTION(aDrawMode == DrawMode::GLYPH_PATH || !aCallbacks, "callback must not be specified unless using GLYPH_PATH");
+
+    bool skipDrawing = mSkipDrawing;
+    if (aDrawMode == DrawMode::GLYPH_FILL) {
+        gfxRGBA currentColor;
+        if (aContext->GetDeviceColor(currentColor) && currentColor.a == 0) {
+            skipDrawing = true;
+        }
+    }
+
+    gfxFloat direction = GetDirection();
+
+    if (skipDrawing) {
+        // We don't need to draw anything;
+        // but if the caller wants advance width, we need to compute it here
+        if (aAdvanceWidth) {
+            gfxTextRun::Metrics metrics = MeasureText(aStart, aLength,
+                                                      gfxFont::LOOSE_INK_EXTENTS,
+                                                      aContext, aProvider);
+            *aAdvanceWidth = metrics.mAdvanceWidth * direction;
+        }
+
+        // return without drawing
+        return;
+    }
+
+    gfxPoint pt = aPt;
+
+    // synthetic bolding draws glyphs twice ==> colors with opacity won't draw correctly unless first drawn without alpha
+    BufferAlphaColor syntheticBoldBuffer(aContext);
+    gfxRGBA currentColor;
+    bool needToRestore = false;
+
+    if (aDrawMode == DrawMode::GLYPH_FILL && HasNonOpaqueColor(aContext, currentColor)
+                                          && HasSyntheticBold(this, aStart, aLength)) {
+        needToRestore = true;
+        // measure text, use the bounding box
+        gfxTextRun::Metrics metrics = MeasureText(aStart, aLength, gfxFont::LOOSE_INK_EXTENTS,
+                                                  aContext, aProvider);
+        metrics.mBoundingBox.MoveBy(aPt);
+        syntheticBoldBuffer.PushSolidColor(metrics.mBoundingBox, currentColor, GetAppUnitsPerDevUnit());
+    }
+
+    GlyphRunIterator iter(this, aStart, aLength);
+    while (iter.NextRun()) {
+        gfxFont *font = iter.GetGlyphRun()->mFont;
+        uint32_t start = iter.GetStringStart();
+        uint32_t end = iter.GetStringEnd();
+        uint32_t ligatureRunStart = start;
+        uint32_t ligatureRunEnd = end;
+        ShrinkToLigatureBoundaries(&ligatureRunStart, &ligatureRunEnd);
+        
+        bool drawPartial = aDrawMode == DrawMode::GLYPH_FILL ||
+                           (aDrawMode == DrawMode::GLYPH_PATH && aCallbacks);
+
+        if (drawPartial) {
+            DrawPartialLigature(font, aContext, start, ligatureRunStart, &pt,
+                                aProvider, aCallbacks);
+        }
+
+        DrawGlyphs(font, aContext, aDrawMode, &pt, aContextPaint, ligatureRunStart,
+                   ligatureRunEnd, aProvider, ligatureRunStart, ligatureRunEnd,
+                   aCallbacks);
+
+        if (drawPartial) {
+            DrawPartialLigature(font, aContext, ligatureRunEnd, end, &pt,
+                                aProvider, aCallbacks);
+        }
+    }
+
+    // composite result when synthetic bolding used
+    if (needToRestore) {
+        syntheticBoldBuffer.PopAlpha();
+    }
+
+    if (aAdvanceWidth) {
+        *aAdvanceWidth = (pt.x - aPt.x)*direction;
+    }
+}
+
+void
+gfxTextRun::AccumulateMetricsForRun(gfxFont *aFont,
+                                    uint32_t aStart, uint32_t aEnd,
+                                    gfxFont::BoundingBoxType aBoundingBoxType,
+                                    gfxContext *aRefContext,
+                                    PropertyProvider *aProvider,
+                                    uint32_t aSpacingStart, uint32_t aSpacingEnd,
+                                    Metrics *aMetrics)
+{
+    nsAutoTArray<PropertyProvider::Spacing,200> spacingBuffer;
+    bool haveSpacing = GetAdjustedSpacingArray(aStart, aEnd, aProvider,
+        aSpacingStart, aSpacingEnd, &spacingBuffer);
+    Metrics metrics = aFont->Measure(this, aStart, aEnd, aBoundingBoxType, aRefContext,
+                                     haveSpacing ? spacingBuffer.Elements() : nullptr);
+    aMetrics->CombineWith(metrics, IsRightToLeft());
+}
+
+void
+gfxTextRun::AccumulatePartialLigatureMetrics(gfxFont *aFont,
+    uint32_t aStart, uint32_t aEnd,
+    gfxFont::BoundingBoxType aBoundingBoxType, gfxContext *aRefContext,
+    PropertyProvider *aProvider, Metrics *aMetrics)
+{
+    if (aStart >= aEnd)
+        return;
+
+    // Measure partial ligature. We hack this by clipping the metrics in the
+    // same way we clip the drawing.
+    LigatureData data = ComputeLigatureData(aStart, aEnd, aProvider);
+
+    // First measure the complete ligature
+    Metrics metrics;
+    AccumulateMetricsForRun(aFont, data.mLigatureStart, data.mLigatureEnd,
+                            aBoundingBoxType, aRefContext,
+                            aProvider, aStart, aEnd, &metrics);
+
+    // Clip the bounding box to the ligature part
+    gfxFloat bboxLeft = metrics.mBoundingBox.X();
+    gfxFloat bboxRight = metrics.mBoundingBox.XMost();
+    // Where we are going to start "drawing" relative to our left baseline origin
+    gfxFloat origin = IsRightToLeft() ? metrics.mAdvanceWidth - data.mPartAdvance : 0;
+    ClipPartialLigature(this, &bboxLeft, &bboxRight, origin, &data);
+    metrics.mBoundingBox.x = bboxLeft;
+    metrics.mBoundingBox.width = bboxRight - bboxLeft;
+
+    // mBoundingBox is now relative to the left baseline origin for the entire
+    // ligature. Shift it left.
+    metrics.mBoundingBox.x -=
+        IsRightToLeft() ? metrics.mAdvanceWidth - (data.mPartAdvance + data.mPartWidth)
+            : data.mPartAdvance;    
+    metrics.mAdvanceWidth = data.mPartWidth;
+
+    aMetrics->CombineWith(metrics, IsRightToLeft());
+}
+
+gfxTextRun::Metrics
+gfxTextRun::MeasureText(uint32_t aStart, uint32_t aLength,
+                        gfxFont::BoundingBoxType aBoundingBoxType,
+                        gfxContext *aRefContext,
+                        PropertyProvider *aProvider)
+{
+    NS_ASSERTION(aStart + aLength <= GetLength(), "Substring out of range");
+
+    Metrics accumulatedMetrics;
+    GlyphRunIterator iter(this, aStart, aLength);
+    while (iter.NextRun()) {
+        gfxFont *font = iter.GetGlyphRun()->mFont;
+        uint32_t start = iter.GetStringStart();
+        uint32_t end = iter.GetStringEnd();
+        uint32_t ligatureRunStart = start;
+        uint32_t ligatureRunEnd = end;
+        ShrinkToLigatureBoundaries(&ligatureRunStart, &ligatureRunEnd);
+
+        AccumulatePartialLigatureMetrics(font, start, ligatureRunStart,
+            aBoundingBoxType, aRefContext, aProvider, &accumulatedMetrics);
+
+        // XXX This sucks. We have to get glyph extents just so we can detect
+        // glyphs outside the font box, even when aBoundingBoxType is LOOSE,
+        // even though in almost all cases we could get correct results just
+        // by getting some ascent/descent from the font and using our stored
+        // advance widths.
+        AccumulateMetricsForRun(font,
+            ligatureRunStart, ligatureRunEnd, aBoundingBoxType,
+            aRefContext, aProvider, ligatureRunStart, ligatureRunEnd,
+            &accumulatedMetrics);
+
+        AccumulatePartialLigatureMetrics(font, ligatureRunEnd, end,
+            aBoundingBoxType, aRefContext, aProvider, &accumulatedMetrics);
+    }
+
+    return accumulatedMetrics;
+}
+
+#define MEASUREMENT_BUFFER_SIZE 100
+
+uint32_t
+gfxTextRun::BreakAndMeasureText(uint32_t aStart, uint32_t aMaxLength,
+                                bool aLineBreakBefore, gfxFloat aWidth,
+                                PropertyProvider *aProvider,
+                                bool aSuppressInitialBreak,
+                                gfxFloat *aTrimWhitespace,
+                                Metrics *aMetrics,
+                                gfxFont::BoundingBoxType aBoundingBoxType,
+                                gfxContext *aRefContext,
+                                bool *aUsedHyphenation,
+                                uint32_t *aLastBreak,
+                                bool aCanWordWrap,
+                                gfxBreakPriority *aBreakPriority)
+{
+    aMaxLength = std::min(aMaxLength, GetLength() - aStart);
+
+    NS_ASSERTION(aStart + aMaxLength <= GetLength(), "Substring out of range");
+
+    uint32_t bufferStart = aStart;
+    uint32_t bufferLength = std::min<uint32_t>(aMaxLength, MEASUREMENT_BUFFER_SIZE);
+    PropertyProvider::Spacing spacingBuffer[MEASUREMENT_BUFFER_SIZE];
+    bool haveSpacing = aProvider && (mFlags & gfxTextRunFactory::TEXT_ENABLE_SPACING) != 0;
+    if (haveSpacing) {
+        GetAdjustedSpacing(this, bufferStart, bufferStart + bufferLength, aProvider,
+                           spacingBuffer);
+    }
+    bool hyphenBuffer[MEASUREMENT_BUFFER_SIZE];
+    bool haveHyphenation = aProvider &&
+        (aProvider->GetHyphensOption() == NS_STYLE_HYPHENS_AUTO ||
+         (aProvider->GetHyphensOption() == NS_STYLE_HYPHENS_MANUAL &&
+          (mFlags & gfxTextRunFactory::TEXT_ENABLE_HYPHEN_BREAKS) != 0));
+    if (haveHyphenation) {
+        aProvider->GetHyphenationBreaks(bufferStart, bufferLength,
+                                        hyphenBuffer);
+    }
+
+    gfxFloat width = 0;
+    gfxFloat advance = 0;
+    // The number of space characters that can be trimmed
+    uint32_t trimmableChars = 0;
+    // The amount of space removed by ignoring trimmableChars
+    gfxFloat trimmableAdvance = 0;
+    int32_t lastBreak = -1;
+    int32_t lastBreakTrimmableChars = -1;
+    gfxFloat lastBreakTrimmableAdvance = -1;
+    bool aborted = false;
+    uint32_t end = aStart + aMaxLength;
+    bool lastBreakUsedHyphenation = false;
+
+    uint32_t ligatureRunStart = aStart;
+    uint32_t ligatureRunEnd = end;
+    ShrinkToLigatureBoundaries(&ligatureRunStart, &ligatureRunEnd);
+
+    uint32_t i;
+    for (i = aStart; i < end; ++i) {
+        if (i >= bufferStart + bufferLength) {
+            // Fetch more spacing and hyphenation data
+            bufferStart = i;
+            bufferLength = std::min(aStart + aMaxLength, i + MEASUREMENT_BUFFER_SIZE) - i;
+            if (haveSpacing) {
+                GetAdjustedSpacing(this, bufferStart, bufferStart + bufferLength, aProvider,
+                                   spacingBuffer);
+            }
+            if (haveHyphenation) {
+                aProvider->GetHyphenationBreaks(bufferStart, bufferLength,
+                                                hyphenBuffer);
+            }
+        }
+
+        // There can't be a word-wrap break opportunity at the beginning of the
+        // line: if the width is too small for even one character to fit, it 
+        // could be the first and last break opportunity on the line, and that
+        // would trigger an infinite loop.
+        if (!aSuppressInitialBreak || i > aStart) {
+            bool atNaturalBreak = mCharacterGlyphs[i].CanBreakBefore() == 1;
+            bool atHyphenationBreak =
+                !atNaturalBreak && haveHyphenation && hyphenBuffer[i - bufferStart];
+            bool atBreak = atNaturalBreak || atHyphenationBreak;
+            bool wordWrapping =
+                aCanWordWrap && mCharacterGlyphs[i].IsClusterStart() &&
+                *aBreakPriority <= gfxBreakPriority::eWordWrapBreak;
+
+            if (atBreak || wordWrapping) {
+                gfxFloat hyphenatedAdvance = advance;
+                if (atHyphenationBreak) {
+                    hyphenatedAdvance += aProvider->GetHyphenWidth();
+                }
+            
+                if (lastBreak < 0 || width + hyphenatedAdvance - trimmableAdvance <= aWidth) {
+                    // We can break here.
+                    lastBreak = i;
+                    lastBreakTrimmableChars = trimmableChars;
+                    lastBreakTrimmableAdvance = trimmableAdvance;
+                    lastBreakUsedHyphenation = atHyphenationBreak;
+                    *aBreakPriority = atBreak ? gfxBreakPriority::eNormalBreak
+                                              : gfxBreakPriority::eWordWrapBreak;
+                }
+
+                width += advance;
+                advance = 0;
+                if (width - trimmableAdvance > aWidth) {
+                    // No more text fits. Abort
+                    aborted = true;
+                    break;
+                }
+            }
+        }
+        
+        gfxFloat charAdvance;
+        if (i >= ligatureRunStart && i < ligatureRunEnd) {
+            charAdvance = GetAdvanceForGlyphs(i, i + 1);
+            if (haveSpacing) {
+                PropertyProvider::Spacing *space = &spacingBuffer[i - bufferStart];
+                charAdvance += space->mBefore + space->mAfter;
+            }
+        } else {
+            charAdvance = ComputePartialLigatureWidth(i, i + 1, aProvider);
+        }
+        
+        advance += charAdvance;
+        if (aTrimWhitespace) {
+            if (mCharacterGlyphs[i].CharIsSpace()) {
+                ++trimmableChars;
+                trimmableAdvance += charAdvance;
+            } else {
+                trimmableAdvance = 0;
+                trimmableChars = 0;
+            }
+        }
+    }
+
+    if (!aborted) {
+        width += advance;
+    }
+
+    // There are three possibilities:
+    // 1) all the text fit (width <= aWidth)
+    // 2) some of the text fit up to a break opportunity (width > aWidth && lastBreak >= 0)
+    // 3) none of the text fits before a break opportunity (width > aWidth && lastBreak < 0)
+    uint32_t charsFit;
+    bool usedHyphenation = false;
+    if (width - trimmableAdvance <= aWidth) {
+        charsFit = aMaxLength;
+    } else if (lastBreak >= 0) {
+        charsFit = lastBreak - aStart;
+        trimmableChars = lastBreakTrimmableChars;
+        trimmableAdvance = lastBreakTrimmableAdvance;
+        usedHyphenation = lastBreakUsedHyphenation;
+    } else {
+        charsFit = aMaxLength;
+    }
+
+    if (aMetrics) {
+        *aMetrics = MeasureText(aStart, charsFit - trimmableChars,
+            aBoundingBoxType, aRefContext, aProvider);
+    }
+    if (aTrimWhitespace) {
+        *aTrimWhitespace = trimmableAdvance;
+    }
+    if (aUsedHyphenation) {
+        *aUsedHyphenation = usedHyphenation;
+    }
+    if (aLastBreak && charsFit == aMaxLength) {
+        if (lastBreak < 0) {
+            *aLastBreak = UINT32_MAX;
+        } else {
+            *aLastBreak = lastBreak - aStart;
+        }
+    }
+
+    return charsFit;
+}
+
+gfxFloat
+gfxTextRun::GetAdvanceWidth(uint32_t aStart, uint32_t aLength,
+                            PropertyProvider *aProvider)
+{
+    NS_ASSERTION(aStart + aLength <= GetLength(), "Substring out of range");
+
+    uint32_t ligatureRunStart = aStart;
+    uint32_t ligatureRunEnd = aStart + aLength;
+    ShrinkToLigatureBoundaries(&ligatureRunStart, &ligatureRunEnd);
+
+    gfxFloat result = ComputePartialLigatureWidth(aStart, ligatureRunStart, aProvider) +
+                      ComputePartialLigatureWidth(ligatureRunEnd, aStart + aLength, aProvider);
+
+    // Account for all remaining spacing here. This is more efficient than
+    // processing it along with the glyphs.
+    if (aProvider && (mFlags & gfxTextRunFactory::TEXT_ENABLE_SPACING)) {
+        uint32_t i;
+        nsAutoTArray<PropertyProvider::Spacing,200> spacingBuffer;
+        if (spacingBuffer.AppendElements(aLength)) {
+            GetAdjustedSpacing(this, ligatureRunStart, ligatureRunEnd, aProvider,
+                               spacingBuffer.Elements());
+            for (i = 0; i < ligatureRunEnd - ligatureRunStart; ++i) {
+                PropertyProvider::Spacing *space = &spacingBuffer[i];
+                result += space->mBefore + space->mAfter;
+            }
+        }
+    }
+
+    return result + GetAdvanceForGlyphs(ligatureRunStart, ligatureRunEnd);
+}
+
+bool
+gfxTextRun::SetLineBreaks(uint32_t aStart, uint32_t aLength,
+                          bool aLineBreakBefore, bool aLineBreakAfter,
+                          gfxFloat *aAdvanceWidthDelta,
+                          gfxContext *aRefContext)
+{
+    // Do nothing because our shaping does not currently take linebreaks into
+    // account. There is no change in advance width.
+    if (aAdvanceWidthDelta) {
+        *aAdvanceWidthDelta = 0;
+    }
+    return false;
+}
+
+uint32_t
+gfxTextRun::FindFirstGlyphRunContaining(uint32_t aOffset)
+{
+    NS_ASSERTION(aOffset <= GetLength(), "Bad offset looking for glyphrun");
+    NS_ASSERTION(GetLength() == 0 || mGlyphRuns.Length() > 0,
+                 "non-empty text but no glyph runs present!");
+    if (aOffset == GetLength())
+        return mGlyphRuns.Length();
+    uint32_t start = 0;
+    uint32_t end = mGlyphRuns.Length();
+    while (end - start > 1) {
+        uint32_t mid = (start + end)/2;
+        if (mGlyphRuns[mid].mCharacterOffset <= aOffset) {
+            start = mid;
+        } else {
+            end = mid;
+        }
+    }
+    NS_ASSERTION(mGlyphRuns[start].mCharacterOffset <= aOffset,
+                 "Hmm, something went wrong, aOffset should have been found");
+    return start;
+}
+
+nsresult
+gfxTextRun::AddGlyphRun(gfxFont *aFont, uint8_t aMatchType,
+                        uint32_t aUTF16Offset, bool aForceNewRun)
+{
+    NS_ASSERTION(aFont, "adding glyph run for null font!");
+    if (!aFont) {
+        return NS_OK;
+    }    
+    uint32_t numGlyphRuns = mGlyphRuns.Length();
+    if (!aForceNewRun && numGlyphRuns > 0) {
+        GlyphRun *lastGlyphRun = &mGlyphRuns[numGlyphRuns - 1];
+
+        NS_ASSERTION(lastGlyphRun->mCharacterOffset <= aUTF16Offset,
+                     "Glyph runs out of order (and run not forced)");
+
+        // Don't append a run if the font is already the one we want
+        if (lastGlyphRun->mFont == aFont &&
+            lastGlyphRun->mMatchType == aMatchType)
+        {
+            return NS_OK;
+        }
+
+        // If the offset has not changed, avoid leaving a zero-length run
+        // by overwriting the last entry instead of appending...
+        if (lastGlyphRun->mCharacterOffset == aUTF16Offset) {
+
+            // ...except that if the run before the last entry had the same
+            // font as the new one wants, merge with it instead of creating
+            // adjacent runs with the same font
+            if (numGlyphRuns > 1 &&
+                mGlyphRuns[numGlyphRuns - 2].mFont == aFont &&
+                mGlyphRuns[numGlyphRuns - 2].mMatchType == aMatchType)
+            {
+                mGlyphRuns.TruncateLength(numGlyphRuns - 1);
+                return NS_OK;
+            }
+
+            lastGlyphRun->mFont = aFont;
+            lastGlyphRun->mMatchType = aMatchType;
+            return NS_OK;
+        }
+    }
+
+    NS_ASSERTION(aForceNewRun || numGlyphRuns > 0 || aUTF16Offset == 0,
+                 "First run doesn't cover the first character (and run not forced)?");
+
+    GlyphRun *glyphRun = mGlyphRuns.AppendElement();
+    if (!glyphRun)
+        return NS_ERROR_OUT_OF_MEMORY;
+    glyphRun->mFont = aFont;
+    glyphRun->mCharacterOffset = aUTF16Offset;
+    glyphRun->mMatchType = aMatchType;
+    return NS_OK;
+}
+
+void
+gfxTextRun::SortGlyphRuns()
+{
+    if (mGlyphRuns.Length() <= 1)
+        return;
+
+    nsTArray<GlyphRun> runs(mGlyphRuns);
+    GlyphRunOffsetComparator comp;
+    runs.Sort(comp);
+
+    // Now copy back, coalescing adjacent glyph runs that have the same font
+    mGlyphRuns.Clear();
+    uint32_t i, count = runs.Length();
+    for (i = 0; i < count; ++i) {
+        // a GlyphRun with the same font as the previous GlyphRun can just
+        // be skipped; the last GlyphRun will cover its character range.
+        if (i == 0 || runs[i].mFont != runs[i - 1].mFont) {
+            mGlyphRuns.AppendElement(runs[i]);
+            // If two fonts have the same character offset, Sort() will have
+            // randomized the order.
+            NS_ASSERTION(i == 0 ||
+                         runs[i].mCharacterOffset !=
+                         runs[i - 1].mCharacterOffset,
+                         "Two fonts for the same run, glyph indices may not match the font");
+        }
+    }
+}
+
+// Note that SanitizeGlyphRuns scans all glyph runs in the textrun;
+// therefore we only call it once, at the end of textrun construction,
+// NOT incrementally as each glyph run is added (bug 680402).
+void
+gfxTextRun::SanitizeGlyphRuns()
+{
+    if (mGlyphRuns.Length() <= 1)
+        return;
+
+    // If any glyph run starts with ligature-continuation characters, we need to advance it
+    // to the first "real" character to avoid drawing partial ligature glyphs from wrong font
+    // (seen with U+FEFF in reftest 474417-1, as Core Text eliminates the glyph, which makes
+    // it appear as if a ligature has been formed)
+    int32_t i, lastRunIndex = mGlyphRuns.Length() - 1;
+    const CompressedGlyph *charGlyphs = mCharacterGlyphs;
+    for (i = lastRunIndex; i >= 0; --i) {
+        GlyphRun& run = mGlyphRuns[i];
+        while (charGlyphs[run.mCharacterOffset].IsLigatureContinuation() &&
+               run.mCharacterOffset < GetLength()) {
+            run.mCharacterOffset++;
+        }
+        // if the run has become empty, eliminate it
+        if ((i < lastRunIndex &&
+             run.mCharacterOffset >= mGlyphRuns[i+1].mCharacterOffset) ||
+            (i == lastRunIndex && run.mCharacterOffset == GetLength())) {
+            mGlyphRuns.RemoveElementAt(i);
+            --lastRunIndex;
+        }
+    }
+}
+
+uint32_t
+gfxTextRun::CountMissingGlyphs()
+{
+    uint32_t i;
+    uint32_t count = 0;
+    for (i = 0; i < GetLength(); ++i) {
+        if (mCharacterGlyphs[i].IsMissing()) {
+            ++count;
+        }
+    }
+    return count;
+}
+
+gfxTextRun::DetailedGlyph *
+gfxTextRun::AllocateDetailedGlyphs(uint32_t aIndex, uint32_t aCount)
+{
+    NS_ASSERTION(aIndex < GetLength(), "Index out of range");
+
+    if (!mDetailedGlyphs) {
+        mDetailedGlyphs = new DetailedGlyphStore();
+    }
+
+    DetailedGlyph *details = mDetailedGlyphs->Allocate(aIndex, aCount);
+    if (!details) {
+        mCharacterGlyphs[aIndex].SetMissing(0);
+        return nullptr;
+    }
+
+    return details;
+}
+
+void
+gfxTextRun::CopyGlyphDataFrom(gfxShapedWord *aShapedWord, uint32_t aOffset)
+{
+    uint32_t wordLen = aShapedWord->GetLength();
+    NS_ASSERTION(aOffset + wordLen <= GetLength(),
+                 "word overruns end of textrun!");
+
+    CompressedGlyph *charGlyphs = GetCharacterGlyphs();
+    const CompressedGlyph *wordGlyphs = aShapedWord->GetCharacterGlyphs();
+    if (aShapedWord->HasDetailedGlyphs()) {
+        for (uint32_t i = 0; i < wordLen; ++i, ++aOffset) {
+            const CompressedGlyph& g = wordGlyphs[i];
+            if (g.IsSimpleGlyph()) {
+                charGlyphs[aOffset] = g;
+            } else {
+                const DetailedGlyph *details =
+                    g.GetGlyphCount() > 0 ?
+                        aShapedWord->GetDetailedGlyphs(i) : nullptr;
+                SetGlyphs(aOffset, g, details);
+            }
+        }
+    } else {
+        memcpy(charGlyphs + aOffset, wordGlyphs,
+               wordLen * sizeof(CompressedGlyph));
+    }
+}
+
+void
+gfxTextRun::CopyGlyphDataFrom(gfxTextRun *aSource, uint32_t aStart,
+                              uint32_t aLength, uint32_t aDest)
+{
+    NS_ASSERTION(aStart + aLength <= aSource->GetLength(),
+                 "Source substring out of range");
+    NS_ASSERTION(aDest + aLength <= GetLength(),
+                 "Destination substring out of range");
+
+    if (aSource->mSkipDrawing) {
+        mSkipDrawing = true;
+    }
+
+    // Copy base glyph data, and DetailedGlyph data where present
+    const CompressedGlyph *srcGlyphs = aSource->mCharacterGlyphs + aStart;
+    CompressedGlyph *dstGlyphs = mCharacterGlyphs + aDest;
+    for (uint32_t i = 0; i < aLength; ++i) {
+        CompressedGlyph g = srcGlyphs[i];
+        g.SetCanBreakBefore(!g.IsClusterStart() ?
+            CompressedGlyph::FLAG_BREAK_TYPE_NONE :
+            dstGlyphs[i].CanBreakBefore());
+        if (!g.IsSimpleGlyph()) {
+            uint32_t count = g.GetGlyphCount();
+            if (count > 0) {
+                DetailedGlyph *dst = AllocateDetailedGlyphs(i + aDest, count);
+                if (dst) {
+                    DetailedGlyph *src = aSource->GetDetailedGlyphs(i + aStart);
+                    if (src) {
+                        ::memcpy(dst, src, count * sizeof(DetailedGlyph));
+                    } else {
+                        g.SetMissing(0);
+                    }
+                } else {
+                    g.SetMissing(0);
+                }
+            }
+        }
+        dstGlyphs[i] = g;
+    }
+
+    // Copy glyph runs
+    GlyphRunIterator iter(aSource, aStart, aLength);
+#ifdef DEBUG
+    gfxFont *lastFont = nullptr;
+#endif
+    while (iter.NextRun()) {
+        gfxFont *font = iter.GetGlyphRun()->mFont;
+        NS_ASSERTION(font != lastFont, "Glyphruns not coalesced?");
+#ifdef DEBUG
+        lastFont = font;
+        uint32_t end = iter.GetStringEnd();
+#endif
+        uint32_t start = iter.GetStringStart();
+
+        // These used to be NS_ASSERTION()s, but WARNING is more appropriate.
+        // Although it's unusual (and not desirable), it's possible for us to assign
+        // different fonts to a base character and a following diacritic.
+        // Example on OSX 10.5/10.6 with default fonts installed:
+        //     data:text/html,<p style="font-family:helvetica, arial, sans-serif;">
+        //                    &%23x043E;&%23x0486;&%23x20;&%23x043E;&%23x0486;
+        // This means the rendering of the cluster will probably not be very good,
+        // but it's the best we can do for now if the specified font only covered the
+        // initial base character and not its applied marks.
+        NS_WARN_IF_FALSE(aSource->IsClusterStart(start),
+                         "Started font run in the middle of a cluster");
+        NS_WARN_IF_FALSE(end == aSource->GetLength() || aSource->IsClusterStart(end),
+                         "Ended font run in the middle of a cluster");
+
+        nsresult rv = AddGlyphRun(font, iter.GetGlyphRun()->mMatchType,
+                                  start - aStart + aDest, false);
+        if (NS_FAILED(rv))
+            return;
+    }
+}
+
+void
+gfxTextRun::SetSpaceGlyph(gfxFont *aFont, gfxContext *aContext,
+                          uint32_t aCharIndex)
+{
+    if (SetSpaceGlyphIfSimple(aFont, aContext, aCharIndex, ' ')) {
+        return;
+    }
+
+    aFont->InitWordCache();
+    static const uint8_t space = ' ';
+    gfxShapedWord *sw = aFont->GetShapedWord(aContext,
+                                             &space, 1,
+                                             HashMix(0, ' '), 
+                                             MOZ_SCRIPT_LATIN,
+                                             mAppUnitsPerDevUnit,
+                                             gfxTextRunFactory::TEXT_IS_8BIT |
+                                             gfxTextRunFactory::TEXT_IS_ASCII |
+                                             gfxTextRunFactory::TEXT_IS_PERSISTENT,
+                                             nullptr);
+    if (sw) {
+        AddGlyphRun(aFont, gfxTextRange::kFontGroup, aCharIndex, false);
+        CopyGlyphDataFrom(sw, aCharIndex);
+    }
+}
+
+bool
+gfxTextRun::SetSpaceGlyphIfSimple(gfxFont *aFont, gfxContext *aContext,
+                                  uint32_t aCharIndex, char16_t aSpaceChar)
+{
+    uint32_t spaceGlyph = aFont->GetSpaceGlyph();
+    if (!spaceGlyph || !CompressedGlyph::IsSimpleGlyphID(spaceGlyph)) {
+        return false;
+    }
+
+    uint32_t spaceWidthAppUnits =
+        NS_lroundf(aFont->GetMetrics().spaceWidth * mAppUnitsPerDevUnit);
+    if (!CompressedGlyph::IsSimpleAdvance(spaceWidthAppUnits)) {
+        return false;
+    }
+
+    AddGlyphRun(aFont, gfxTextRange::kFontGroup, aCharIndex, false);
+    CompressedGlyph g;
+    g.SetSimpleGlyph(spaceWidthAppUnits, spaceGlyph);
+    if (aSpaceChar == ' ') {
+        g.SetIsSpace();
+    }
+    GetCharacterGlyphs()[aCharIndex] = g;
+    return true;
+}
+
+void
+gfxTextRun::FetchGlyphExtents(gfxContext *aRefContext)
+{
+    bool needsGlyphExtents = NeedsGlyphExtents(this);
+    if (!needsGlyphExtents && !mDetailedGlyphs)
+        return;
+
+    uint32_t i, runCount = mGlyphRuns.Length();
+    CompressedGlyph *charGlyphs = mCharacterGlyphs;
+    for (i = 0; i < runCount; ++i) {
+        const GlyphRun& run = mGlyphRuns[i];
+        gfxFont *font = run.mFont;
+        uint32_t start = run.mCharacterOffset;
+        uint32_t end = i + 1 < runCount ?
+            mGlyphRuns[i + 1].mCharacterOffset : GetLength();
+        bool fontIsSetup = false;
+        uint32_t j;
+        gfxGlyphExtents *extents = font->GetOrCreateGlyphExtents(mAppUnitsPerDevUnit);
+  
+        for (j = start; j < end; ++j) {
+            const gfxTextRun::CompressedGlyph *glyphData = &charGlyphs[j];
+            if (glyphData->IsSimpleGlyph()) {
+                // If we're in speed mode, don't set up glyph extents here; we'll
+                // just return "optimistic" glyph bounds later
+                if (needsGlyphExtents) {
+                    uint32_t glyphIndex = glyphData->GetSimpleGlyph();
+                    if (!extents->IsGlyphKnown(glyphIndex)) {
+                        if (!fontIsSetup) {
+                            if (!font->SetupCairoFont(aRefContext)) {
+                                NS_WARNING("failed to set up font for glyph extents");
+                                break;
+                            }
+                            fontIsSetup = true;
+                        }
+#ifdef DEBUG_TEXT_RUN_STORAGE_METRICS
+                        ++gGlyphExtentsSetupEagerSimple;
+#endif
+                        font->SetupGlyphExtents(aRefContext, glyphIndex, false, extents);
+                    }
+                }
+            } else if (!glyphData->IsMissing()) {
+                uint32_t glyphCount = glyphData->GetGlyphCount();
+                if (glyphCount == 0) {
+                    continue;
+                }
+                const gfxTextRun::DetailedGlyph *details = GetDetailedGlyphs(j);
+                if (!details) {
+                    continue;
+                }
+                for (uint32_t k = 0; k < glyphCount; ++k, ++details) {
+                    uint32_t glyphIndex = details->mGlyphID;
+                    if (!extents->IsGlyphKnownWithTightExtents(glyphIndex)) {
+                        if (!fontIsSetup) {
+                            if (!font->SetupCairoFont(aRefContext)) {
+                                NS_WARNING("failed to set up font for glyph extents");
+                                break;
+                            }
+                            fontIsSetup = true;
+                        }
+#ifdef DEBUG_TEXT_RUN_STORAGE_METRICS
+                        ++gGlyphExtentsSetupEagerTight;
+#endif
+                        font->SetupGlyphExtents(aRefContext, glyphIndex, true, extents);
+                    }
+                }
+            }
+        }
+    }
+}
+
+
+gfxTextRun::ClusterIterator::ClusterIterator(gfxTextRun *aTextRun)
+    : mTextRun(aTextRun), mCurrentChar(uint32_t(-1))
+{
+}
+
+void
+gfxTextRun::ClusterIterator::Reset()
+{
+    mCurrentChar = uint32_t(-1);
+}
+
+bool
+gfxTextRun::ClusterIterator::NextCluster()
+{
+    uint32_t len = mTextRun->GetLength();
+    while (++mCurrentChar < len) {
+        if (mTextRun->IsClusterStart(mCurrentChar)) {
+            return true;
+        }
+    }
+
+    mCurrentChar = uint32_t(-1);
+    return false;
+}
+
+uint32_t
+gfxTextRun::ClusterIterator::ClusterLength() const
+{
+    if (mCurrentChar == uint32_t(-1)) {
+        return 0;
+    }
+
+    uint32_t i = mCurrentChar,
+             len = mTextRun->GetLength();
+    while (++i < len) {
+        if (mTextRun->IsClusterStart(i)) {
+            break;
+        }
+    }
+
+    return i - mCurrentChar;
+}
+
+gfxFloat
+gfxTextRun::ClusterIterator::ClusterAdvance(PropertyProvider *aProvider) const
+{
+    if (mCurrentChar == uint32_t(-1)) {
+        return 0;
+    }
+
+    return mTextRun->GetAdvanceWidth(mCurrentChar, ClusterLength(), aProvider);
+}
+
+size_t
+gfxTextRun::SizeOfExcludingThis(MallocSizeOf aMallocSizeOf)
+{
+    // The second arg is how much gfxTextRun::AllocateStorage would have
+    // allocated.
+    size_t total = mGlyphRuns.SizeOfExcludingThis(aMallocSizeOf);
+
+    if (mDetailedGlyphs) {
+        total += mDetailedGlyphs->SizeOfIncludingThis(aMallocSizeOf);
+    }
+
+    return total;
+}
+
+size_t
+gfxTextRun::SizeOfIncludingThis(MallocSizeOf aMallocSizeOf)
+{
+    return aMallocSizeOf(this) + SizeOfExcludingThis(aMallocSizeOf);
+}
+
+
+#ifdef DEBUG
+void
+gfxTextRun::Dump(FILE* aOutput) {
+    if (!aOutput) {
+        aOutput = stdout;
+    }
+
+    uint32_t i;
+    fputc('[', aOutput);
+    for (i = 0; i < mGlyphRuns.Length(); ++i) {
+        if (i > 0) {
+            fputc(',', aOutput);
+        }
+        gfxFont* font = mGlyphRuns[i].mFont;
+        const gfxFontStyle* style = font->GetStyle();
+        NS_ConvertUTF16toUTF8 fontName(font->GetName());
+        nsAutoCString lang;
+        style->language->ToUTF8String(lang);
+        fprintf(aOutput, "%d: %s %f/%d/%d/%s", mGlyphRuns[i].mCharacterOffset,
+                fontName.get(), style->size,
+                style->weight, style->style, lang.get());
+    }
+    fputc(']', aOutput);
+}
+#endif