The Tor Browser: gfx/thebes/gfxGraphiteShaper.cpp@97036ab72558 (annotated)

gfx/thebes/gfxGraphiteShaper.cpp@97036ab72558 (annotated)

gfx/thebes/gfxGraphiteShaper.cpp

Tue, 06 Jan 2015 21:39:09 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Tue, 06 Jan 2015 21:39:09 +0100
branch: TOR_BUG_9701
changeset 8: 97036ab72558
permissions: -rw-r--r--

Conditionally force memory storage according to privacy.thirdparty.isolate;
This solves Tor bug #9701, complying with disk avoidance documented in
https://www.torproject.org/projects/torbrowser/design/#disk-avoidance.

 /* -*- 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 "gfxGraphiteShaper.h"
 #include "nsString.h"
 #include "gfxContext.h"
 #include "graphite2/Font.h"
 #include "graphite2/Segment.h"
 #include "harfbuzz/hb.h"
 #define FloatToFixed(f) (65536 * (f))
 #define FixedToFloat(f) ((f) * (1.0 / 65536.0))
 // Right shifts of negative (signed) integers are undefined, as are overflows
 // when converting unsigned to negative signed integers.
 // (If speed were an issue we could make some 2's complement assumptions.)
 #define FixedToIntRound(f) ((f) > 0 ?  ((32768 + (f)) >> 16) \
                                     : -((32767 - (f)) >> 16))
 using namespace mozilla; // for AutoSwap_* types
 /*
  * Creation and destruction; on deletion, release any font tables we're holding
  */
 gfxGraphiteShaper::gfxGraphiteShaper(gfxFont *aFont)
     : gfxFontShaper(aFont),
       mGrFace(mFont->GetFontEntry()->GetGrFace()),
       mGrFont(nullptr)
 {
     mCallbackData.mFont = aFont;
     mCallbackData.mShaper = this;
 }
 gfxGraphiteShaper::~gfxGraphiteShaper()
 {
     if (mGrFont) {
         gr_font_destroy(mGrFont);
     }
     mFont->GetFontEntry()->ReleaseGrFace(mGrFace);
 }
 /*static*/ float
 gfxGraphiteShaper::GrGetAdvance(const void* appFontHandle, uint16_t glyphid)
 {
     const CallbackData *cb =
         static_cast<const CallbackData*>(appFontHandle);
     return FixedToFloat(cb->mFont->GetGlyphWidth(cb->mContext, glyphid));
 }
 static inline uint32_t
 MakeGraphiteLangTag(uint32_t aTag)
 {
     uint32_t grLangTag = aTag;
     // replace trailing space-padding with NULs for graphite
     uint32_t mask = 0x000000FF;
     while ((grLangTag & mask) == ' ') {
         grLangTag &= ~mask;
         mask <<= 8;
     }
     return grLangTag;
 }
 struct GrFontFeatures {
     gr_face        *mFace;
     gr_feature_val *mFeatures;
 };
 static PLDHashOperator
 AddFeature(const uint32_t& aTag, uint32_t& aValue, void *aUserArg)
 {
     GrFontFeatures *f = static_cast<GrFontFeatures*>(aUserArg);
     const gr_feature_ref* fref = gr_face_find_fref(f->mFace, aTag);
     if (fref) {
         gr_fref_set_feature_value(fref, aValue, f->mFeatures);
     }
     return PL_DHASH_NEXT;
 }
 bool
 gfxGraphiteShaper::ShapeText(gfxContext      *aContext,
                              const char16_t *aText,
                              uint32_t         aOffset,
                              uint32_t         aLength,
                              int32_t          aScript,
                              gfxShapedText   *aShapedText)
 {
     // some font back-ends require this in order to get proper hinted metrics
     if (!mFont->SetupCairoFont(aContext)) {
         return false;
     }
     mCallbackData.mContext = aContext;
     if (!mGrFont) {
         if (!mGrFace) {
             return false;
         }
         if (mFont->ProvidesGlyphWidths()) {
             gr_font_ops ops = {
                 sizeof(gr_font_ops),
                 &GrGetAdvance,
                 nullptr // vertical text not yet implemented
             };
             mGrFont = gr_make_font_with_ops(mFont->GetAdjustedSize(),
                                             &mCallbackData, &ops, mGrFace);
         } else {
             mGrFont = gr_make_font(mFont->GetAdjustedSize(), mGrFace);
         }
         if (!mGrFont) {
             return false;
         }
     }
     gfxFontEntry *entry = mFont->GetFontEntry();
     const gfxFontStyle *style = mFont->GetStyle();
     uint32_t grLang = 0;
     if (style->languageOverride) {
         grLang = MakeGraphiteLangTag(style->languageOverride);
     } else if (entry->mLanguageOverride) {
         grLang = MakeGraphiteLangTag(entry->mLanguageOverride);
     } else {
         nsAutoCString langString;
         style->language->ToUTF8String(langString);
         grLang = GetGraphiteTagForLang(langString);
     }
     gr_feature_val *grFeatures = gr_face_featureval_for_lang(mGrFace, grLang);
     nsDataHashtable<nsUint32HashKey,uint32_t> mergedFeatures;
     // if style contains font-specific features
     if (MergeFontFeatures(style,
                           mFont->GetFontEntry()->mFeatureSettings,
                           aShapedText->DisableLigatures(),
                           mFont->GetFontEntry()->FamilyName(),
                           mergedFeatures))
     {
         // enumerate result and insert into Graphite feature list
         GrFontFeatures f = {mGrFace, grFeatures};
         mergedFeatures.Enumerate(AddFeature, &f);
     }
     size_t numChars = gr_count_unicode_characters(gr_utf16,
                                                   aText, aText + aLength,
                                                   nullptr);
     gr_segment *seg = gr_make_seg(mGrFont, mGrFace, 0, grFeatures,
                                   gr_utf16, aText, numChars,
                                   aShapedText->IsRightToLeft());
     gr_featureval_destroy(grFeatures);
     if (!seg) {
         return false;
     }
     nsresult rv = SetGlyphsFromSegment(aContext, aShapedText, aOffset, aLength,
                                        aText, seg);
     gr_seg_destroy(seg);
     return NS_SUCCEEDED(rv);
 }
 #define SMALL_GLYPH_RUN 256 // avoid heap allocation of per-glyph data arrays
                             // for short (typical) runs up to this length
 struct Cluster {
     uint32_t baseChar; // in UTF16 code units, not Unicode character indices
     uint32_t baseGlyph;
     uint32_t nChars; // UTF16 code units
     uint32_t nGlyphs;
     Cluster() : baseChar(0), baseGlyph(0), nChars(0), nGlyphs(0) { }
 };
 nsresult
 gfxGraphiteShaper::SetGlyphsFromSegment(gfxContext      *aContext,
                                         gfxShapedText   *aShapedText,
                                         uint32_t         aOffset,
                                         uint32_t         aLength,
                                         const char16_t *aText,
                                         gr_segment      *aSegment)
 {
     int32_t dev2appUnits = aShapedText->GetAppUnitsPerDevUnit();
     bool rtl = aShapedText->IsRightToLeft();
     uint32_t glyphCount = gr_seg_n_slots(aSegment);
     // identify clusters; graphite may have reordered/expanded/ligated glyphs.
     AutoFallibleTArray<Cluster,SMALL_GLYPH_RUN> clusters;
     AutoFallibleTArray<uint16_t,SMALL_GLYPH_RUN> gids;
     AutoFallibleTArray<float,SMALL_GLYPH_RUN> xLocs;
     AutoFallibleTArray<float,SMALL_GLYPH_RUN> yLocs;
     if (!clusters.SetLength(aLength) ||
         !gids.SetLength(glyphCount) ||
         !xLocs.SetLength(glyphCount) ||
         !yLocs.SetLength(glyphCount))
     {
         return NS_ERROR_OUT_OF_MEMORY;
     }
     // walk through the glyph slots and check which original character
     // each is associated with
     uint32_t gIndex = 0; // glyph slot index
     uint32_t cIndex = 0; // current cluster index
     for (const gr_slot *slot = gr_seg_first_slot(aSegment);
          slot != nullptr;
          slot = gr_slot_next_in_segment(slot), gIndex++)
     {
         uint32_t before =
             gr_cinfo_base(gr_seg_cinfo(aSegment, gr_slot_before(slot)));
         uint32_t after =
             gr_cinfo_base(gr_seg_cinfo(aSegment, gr_slot_after(slot)));
         gids[gIndex] = gr_slot_gid(slot);
         xLocs[gIndex] = gr_slot_origin_X(slot);
         yLocs[gIndex] = gr_slot_origin_Y(slot);
         // if this glyph has a "before" character index that precedes the
         // current cluster's char index, we need to merge preceding
         // clusters until it gets included
         while (before < clusters[cIndex].baseChar && cIndex > 0) {
             clusters[cIndex-1].nChars += clusters[cIndex].nChars;
             clusters[cIndex-1].nGlyphs += clusters[cIndex].nGlyphs;
             --cIndex;
         }
         // if there's a gap between the current cluster's base character and
         // this glyph's, extend the cluster to include the intervening chars
         if (gr_slot_can_insert_before(slot) && clusters[cIndex].nChars &&
             before >= clusters[cIndex].baseChar + clusters[cIndex].nChars)
         {
             NS_ASSERTION(cIndex < aLength - 1, "cIndex at end of word");
             Cluster& c = clusters[cIndex + 1];
             c.baseChar = clusters[cIndex].baseChar + clusters[cIndex].nChars;
             c.nChars = before - c.baseChar;
             c.baseGlyph = gIndex;
             c.nGlyphs = 0;
             ++cIndex;
         }
         // increment cluster's glyph count to include current slot
         NS_ASSERTION(cIndex < aLength, "cIndex beyond word length");
         ++clusters[cIndex].nGlyphs;
         // extend cluster if necessary to reach the glyph's "after" index
         if (clusters[cIndex].baseChar + clusters[cIndex].nChars < after + 1) {
             clusters[cIndex].nChars = after + 1 - clusters[cIndex].baseChar;
         }
     }
     bool roundX;
     bool roundY;
     aContext->GetRoundOffsetsToPixels(&roundX, &roundY);
     gfxShapedText::CompressedGlyph *charGlyphs =
         aShapedText->GetCharacterGlyphs() + aOffset;
     // now put glyphs into the textrun, one cluster at a time
     for (uint32_t i = 0; i <= cIndex; ++i) {
         const Cluster& c = clusters[i];
         float adv; // total advance of the cluster
         if (rtl) {
             if (i == 0) {
                 adv = gr_seg_advance_X(aSegment) - xLocs[c.baseGlyph];
             } else {
                 adv = xLocs[clusters[i-1].baseGlyph] - xLocs[c.baseGlyph];
             }
         } else {
             if (i == cIndex) {
                 adv = gr_seg_advance_X(aSegment) - xLocs[c.baseGlyph];
             } else {
                 adv = xLocs[clusters[i+1].baseGlyph] - xLocs[c.baseGlyph];
             }
         }
         // Check for default-ignorable char that didn't get filtered, combined,
         // etc by the shaping process, and skip it.
         uint32_t offs = c.baseChar;
         NS_ASSERTION(offs < aLength, "unexpected offset");
         if (c.nGlyphs == 1 && c.nChars == 1 &&
             aShapedText->FilterIfIgnorable(aOffset + offs, aText[offs])) {
             continue;
         }
         uint32_t appAdvance = roundX ? NSToIntRound(adv) * dev2appUnits :
                                        NSToIntRound(adv * dev2appUnits);
         if (c.nGlyphs == 1 &&
             gfxShapedText::CompressedGlyph::IsSimpleGlyphID(gids[c.baseGlyph]) &&
             gfxShapedText::CompressedGlyph::IsSimpleAdvance(appAdvance) &&
             charGlyphs[offs].IsClusterStart() &&
             yLocs[c.baseGlyph] == 0)
         {
             charGlyphs[offs].SetSimpleGlyph(appAdvance, gids[c.baseGlyph]);
         } else {
             // not a one-to-one mapping with simple metrics: use DetailedGlyph
             nsAutoTArray<gfxShapedText::DetailedGlyph,8> details;
             float clusterLoc;
             for (uint32_t j = c.baseGlyph; j < c.baseGlyph + c.nGlyphs; ++j) {
                 gfxShapedText::DetailedGlyph* d = details.AppendElement();
                 d->mGlyphID = gids[j];
                 d->mYOffset = roundY ? NSToIntRound(-yLocs[j]) * dev2appUnits :
                               -yLocs[j] * dev2appUnits;
                 if (j == c.baseGlyph) {
                     d->mXOffset = 0;
                     d->mAdvance = appAdvance;
                     clusterLoc = xLocs[j];
                 } else {
                     float dx = rtl ? (xLocs[j] - clusterLoc) :
                                      (xLocs[j] - clusterLoc - adv);
                     d->mXOffset = roundX ? NSToIntRound(dx) * dev2appUnits :
                                            dx * dev2appUnits;
                     d->mAdvance = 0;
                 }
             }
             gfxShapedText::CompressedGlyph g;
             g.SetComplex(charGlyphs[offs].IsClusterStart(),
                          true, details.Length());
             aShapedText->SetGlyphs(aOffset + offs, g, details.Elements());
         }
         for (uint32_t j = c.baseChar + 1; j < c.baseChar + c.nChars; ++j) {
             NS_ASSERTION(j < aLength, "unexpected offset");
             gfxShapedText::CompressedGlyph &g = charGlyphs[j];
             NS_ASSERTION(!g.IsSimpleGlyph(), "overwriting a simple glyph");
             g.SetComplex(g.IsClusterStart(), false, 0);
         }
     }
     return NS_OK;
 }
 #undef SMALL_GLYPH_RUN
 // for language tag validation - include list of tags from the IANA registry
 #include "gfxLanguageTagList.cpp"
 nsTHashtable<nsUint32HashKey> *gfxGraphiteShaper::sLanguageTags;
 /*static*/ uint32_t
 gfxGraphiteShaper::GetGraphiteTagForLang(const nsCString& aLang)
 {
     int len = aLang.Length();
     if (len < 2) {
         return 0;
     }
     // convert primary language subtag to a left-packed, NUL-padded integer
     // for the Graphite API
     uint32_t grLang = 0;
     for (int i = 0; i < 4; ++i) {
         grLang <<= 8;
         if (i < len) {
             uint8_t ch = aLang[i];
             if (ch == '-') {
                 // found end of primary language subtag, truncate here
                 len = i;
                 continue;
             }
             if (ch < 'a' || ch > 'z') {
                 // invalid character in tag, so ignore it completely
                 return 0;
             }
             grLang += ch;
         }
     }
     // valid tags must have length = 2 or 3
     if (len < 2 || len > 3) {
         return 0;
     }
     if (!sLanguageTags) {
         // store the registered IANA tags in a hash for convenient validation
         sLanguageTags = new nsTHashtable<nsUint32HashKey>(ArrayLength(sLanguageTagList));
         for (const uint32_t *tag = sLanguageTagList; *tag != 0; ++tag) {
             sLanguageTags->PutEntry(*tag);
         }
     }
     // only accept tags known in the IANA registry
     if (sLanguageTags->GetEntry(grLang)) {
         return grLang;
     }
     return 0;
 }
 /*static*/ void
 gfxGraphiteShaper::Shutdown()
 {
 #ifdef NS_FREE_PERMANENT_DATA
     if (sLanguageTags) {
         sLanguageTags->Clear();
         delete sLanguageTags;
         sLanguageTags = nullptr;
     }
 #endif
 }

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gfx/thebes/gfxGraphiteShaper.cpp@97036ab72558 (annotated)

gfx/thebes/gfxGraphiteShaper.cpp