michael@0: /* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 4 -*-
michael@0:  * This Source Code Form is subject to the terms of the Mozilla Public
michael@0:  * License, v. 2.0. If a copy of the MPL was not distributed with this
michael@0:  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0: 
michael@0: #include "gfxFT2FontBase.h"
michael@0: #include "gfxFT2Utils.h"
michael@0: #include "mozilla/Likely.h"
michael@0: #include FT_TRUETYPE_TAGS_H
michael@0: #include FT_TRUETYPE_TABLES_H
michael@0: #include <algorithm>
michael@0: 
michael@0: #ifdef HAVE_FONTCONFIG_FCFREETYPE_H
michael@0: #include <fontconfig/fcfreetype.h>
michael@0: #endif
michael@0: 
michael@0: #include "prlink.h"
michael@0: 
michael@0: // aScale is intended for a 16.16 x/y_scale of an FT_Size_Metrics
michael@0: static inline FT_Long
michael@0: ScaleRoundDesignUnits(FT_Short aDesignMetric, FT_Fixed aScale)
michael@0: {
michael@0:     FT_Long fixed26dot6 = FT_MulFix(aDesignMetric, aScale);
michael@0:     return ROUND_26_6_TO_INT(fixed26dot6);
michael@0: }
michael@0: 
michael@0: // Snap a line to pixels while keeping the center and size of the line as
michael@0: // close to the original position as possible.
michael@0: //
michael@0: // Pango does similar snapping for underline and strikethrough when fonts are
michael@0: // hinted, but nsCSSRendering::GetTextDecorationRectInternal always snaps the
michael@0: // top and size of lines.  Optimizing the distance between the line and
michael@0: // baseline is probably good for the gap between text and underline, but
michael@0: // optimizing the center of the line is better for positioning strikethough.
michael@0: static void
michael@0: SnapLineToPixels(gfxFloat& aOffset, gfxFloat& aSize)
michael@0: {
michael@0:     gfxFloat snappedSize = std::max(floor(aSize + 0.5), 1.0);
michael@0:     // Correct offset for change in size
michael@0:     gfxFloat offset = aOffset - 0.5 * (aSize - snappedSize);
michael@0:     // Snap offset
michael@0:     aOffset = floor(offset + 0.5);
michael@0:     aSize = snappedSize;
michael@0: }
michael@0: 
michael@0: void
michael@0: gfxFT2LockedFace::GetMetrics(gfxFont::Metrics* aMetrics,
michael@0:                              uint32_t* aSpaceGlyph)
michael@0: {
michael@0:     NS_PRECONDITION(aMetrics != nullptr, "aMetrics must not be NULL");
michael@0:     NS_PRECONDITION(aSpaceGlyph != nullptr, "aSpaceGlyph must not be NULL");
michael@0: 
michael@0:     if (MOZ_UNLIKELY(!mFace)) {
michael@0:         // No face.  This unfortunate situation might happen if the font
michael@0:         // file is (re)moved at the wrong time.
michael@0:         const gfxFloat emHeight = mGfxFont->GetStyle()->size;
michael@0:         aMetrics->emHeight = emHeight;
michael@0:         aMetrics->maxAscent = aMetrics->emAscent = 0.8 * emHeight;
michael@0:         aMetrics->maxDescent = aMetrics->emDescent = 0.2 * emHeight;
michael@0:         aMetrics->maxHeight = emHeight;
michael@0:         aMetrics->internalLeading = 0.0;
michael@0:         aMetrics->externalLeading = 0.2 * emHeight;
michael@0:         const gfxFloat spaceWidth = 0.5 * emHeight;
michael@0:         aMetrics->spaceWidth = spaceWidth;
michael@0:         aMetrics->maxAdvance = spaceWidth;
michael@0:         aMetrics->aveCharWidth = spaceWidth;
michael@0:         aMetrics->zeroOrAveCharWidth = spaceWidth;
michael@0:         const gfxFloat xHeight = 0.5 * emHeight;
michael@0:         aMetrics->xHeight = xHeight;
michael@0:         aMetrics->superscriptOffset = xHeight;
michael@0:         aMetrics->subscriptOffset = xHeight;
michael@0:         const gfxFloat underlineSize = emHeight / 14.0;
michael@0:         aMetrics->underlineSize = underlineSize;
michael@0:         aMetrics->underlineOffset = -underlineSize;
michael@0:         aMetrics->strikeoutOffset = 0.25 * emHeight;
michael@0:         aMetrics->strikeoutSize = underlineSize;
michael@0: 
michael@0:         *aSpaceGlyph = 0;
michael@0:         return;
michael@0:     }
michael@0: 
michael@0:     const FT_Size_Metrics& ftMetrics = mFace->size->metrics;
michael@0: 
michael@0:     gfxFloat emHeight;
michael@0:     // Scale for vertical design metric conversion: pixels per design unit.
michael@0:     // If this remains at 0.0, we can't use metrics from OS/2 etc.
michael@0:     gfxFloat yScale = 0.0;
michael@0:     if (FT_IS_SCALABLE(mFace)) {
michael@0:         // Prefer FT_Size_Metrics::x_scale to x_ppem as x_ppem does not
michael@0:         // have subpixel accuracy.
michael@0:         //
michael@0:         // FT_Size_Metrics::y_scale is in 16.16 fixed point format.  Its
michael@0:         // (fractional) value is a factor that converts vertical metrics from
michael@0:         // design units to units of 1/64 pixels, so that the result may be
michael@0:         // interpreted as pixels in 26.6 fixed point format.
michael@0:         yScale = FLOAT_FROM_26_6(FLOAT_FROM_16_16(ftMetrics.y_scale));
michael@0:         emHeight = mFace->units_per_EM * yScale;
michael@0:     } else { // Not scalable.
michael@0:         emHeight = ftMetrics.y_ppem;
michael@0:         // FT_Face doc says units_per_EM and a bunch of following fields
michael@0:         // are "only relevant to scalable outlines". If it's an sfnt,
michael@0:         // we can get units_per_EM from the 'head' table instead; otherwise,
michael@0:         // we don't have a unitsPerEm value so we can't compute/use yScale.
michael@0:         const TT_Header* head =
michael@0:             static_cast<TT_Header*>(FT_Get_Sfnt_Table(mFace, ft_sfnt_head));
michael@0:         if (head) {
michael@0:             gfxFloat emUnit = head->Units_Per_EM;
michael@0:             yScale = emHeight / emUnit;
michael@0:         }
michael@0:     }
michael@0: 
michael@0:     TT_OS2 *os2 =
michael@0:         static_cast<TT_OS2*>(FT_Get_Sfnt_Table(mFace, ft_sfnt_os2));
michael@0: 
michael@0:     aMetrics->maxAscent = FLOAT_FROM_26_6(ftMetrics.ascender);
michael@0:     aMetrics->maxDescent = -FLOAT_FROM_26_6(ftMetrics.descender);
michael@0:     aMetrics->maxAdvance = FLOAT_FROM_26_6(ftMetrics.max_advance);
michael@0: 
michael@0:     gfxFloat lineHeight;
michael@0:     if (os2 && os2->sTypoAscender && yScale > 0.0) {
michael@0:         aMetrics->emAscent = os2->sTypoAscender * yScale;
michael@0:         aMetrics->emDescent = -os2->sTypoDescender * yScale;
michael@0:         FT_Short typoHeight =
michael@0:             os2->sTypoAscender - os2->sTypoDescender + os2->sTypoLineGap;
michael@0:         lineHeight = typoHeight * yScale;
michael@0: 
michael@0:         // If the OS/2 fsSelection USE_TYPO_METRICS bit is set,
michael@0:         // or if this is an OpenType Math font,
michael@0:         // set maxAscent/Descent from the sTypo* fields instead of hhea.
michael@0:         const uint16_t kUseTypoMetricsMask = 1 << 7;
michael@0:         FT_ULong length = 0;
michael@0:         if ((os2->fsSelection & kUseTypoMetricsMask) ||
michael@0:             0 == FT_Load_Sfnt_Table(mFace, FT_MAKE_TAG('M','A','T','H'),
michael@0:                                     0, nullptr, &length)) {
michael@0:             aMetrics->maxAscent = NS_round(aMetrics->emAscent);
michael@0:             aMetrics->maxDescent = NS_round(aMetrics->emDescent);
michael@0:         } else {
michael@0:             // maxAscent/maxDescent get used for frame heights, and some fonts
michael@0:             // don't have the HHEA table ascent/descent set (bug 279032).
michael@0:             // We use NS_round here to parallel the pixel-rounded values that
michael@0:             // freetype gives us for ftMetrics.ascender/descender.
michael@0:             aMetrics->maxAscent =
michael@0:                 std::max(aMetrics->maxAscent, NS_round(aMetrics->emAscent));
michael@0:             aMetrics->maxDescent =
michael@0:                 std::max(aMetrics->maxDescent, NS_round(aMetrics->emDescent));
michael@0:         }
michael@0:     } else {
michael@0:         aMetrics->emAscent = aMetrics->maxAscent;
michael@0:         aMetrics->emDescent = aMetrics->maxDescent;
michael@0:         lineHeight = FLOAT_FROM_26_6(ftMetrics.height);
michael@0:     }
michael@0: 
michael@0:     cairo_text_extents_t extents;
michael@0:     *aSpaceGlyph = GetCharExtents(' ', &extents);
michael@0:     if (*aSpaceGlyph) {
michael@0:         aMetrics->spaceWidth = extents.x_advance;
michael@0:     } else {
michael@0:         aMetrics->spaceWidth = aMetrics->maxAdvance; // guess
michael@0:     }
michael@0: 
michael@0:     aMetrics->zeroOrAveCharWidth = 0.0;
michael@0:     if (GetCharExtents('0', &extents)) {
michael@0:         aMetrics->zeroOrAveCharWidth = extents.x_advance;
michael@0:     }
michael@0: 
michael@0:     // Prefering a measured x over sxHeight because sxHeight doesn't consider
michael@0:     // hinting, but maybe the x extents are not quite right in some fancy
michael@0:     // script fonts.  CSS 2.1 suggests possibly using the height of an "o",
michael@0:     // which would have a more consistent glyph across fonts.
michael@0:     if (GetCharExtents('x', &extents) && extents.y_bearing < 0.0) {
michael@0:         aMetrics->xHeight = -extents.y_bearing;
michael@0:         aMetrics->aveCharWidth = extents.x_advance;
michael@0:     } else {
michael@0:         if (os2 && os2->sxHeight && yScale > 0.0) {
michael@0:             aMetrics->xHeight = os2->sxHeight * yScale;
michael@0:         } else {
michael@0:             // CSS 2.1, section 4.3.2 Lengths: "In the cases where it is
michael@0:             // impossible or impractical to determine the x-height, a value of
michael@0:             // 0.5em should be used."
michael@0:             aMetrics->xHeight = 0.5 * emHeight;
michael@0:         }
michael@0:         aMetrics->aveCharWidth = 0.0; // updated below
michael@0:     }
michael@0:     // aveCharWidth is used for the width of text input elements so be
michael@0:     // liberal rather than conservative in the estimate.
michael@0:     if (os2 && os2->xAvgCharWidth) {
michael@0:         // Round to pixels as this is compared with maxAdvance to guess
michael@0:         // whether this is a fixed width font.
michael@0:         gfxFloat avgCharWidth =
michael@0:             ScaleRoundDesignUnits(os2->xAvgCharWidth, ftMetrics.x_scale);
michael@0:         aMetrics->aveCharWidth =
michael@0:             std::max(aMetrics->aveCharWidth, avgCharWidth);
michael@0:     }
michael@0:     aMetrics->aveCharWidth =
michael@0:         std::max(aMetrics->aveCharWidth, aMetrics->zeroOrAveCharWidth);
michael@0:     if (aMetrics->aveCharWidth == 0.0) {
michael@0:         aMetrics->aveCharWidth = aMetrics->spaceWidth;
michael@0:     }
michael@0:     if (aMetrics->zeroOrAveCharWidth == 0.0) {
michael@0:         aMetrics->zeroOrAveCharWidth = aMetrics->aveCharWidth;
michael@0:     }
michael@0:     // Apparently hinting can mean that max_advance is not always accurate.
michael@0:     aMetrics->maxAdvance =
michael@0:         std::max(aMetrics->maxAdvance, aMetrics->aveCharWidth);
michael@0: 
michael@0:     // gfxFont::Metrics::underlineOffset is the position of the top of the
michael@0:     // underline.
michael@0:     //
michael@0:     // FT_FaceRec documentation describes underline_position as "the
michael@0:     // center of the underlining stem".  This was the original definition
michael@0:     // of the PostScript metric, but in the PostScript table of OpenType
michael@0:     // fonts the metric is "the top of the underline"
michael@0:     // (http://www.microsoft.com/typography/otspec/post.htm), and FreeType
michael@0:     // (up to version 2.3.7) doesn't make any adjustment.
michael@0:     //
michael@0:     // Therefore get the underline position directly from the table
michael@0:     // ourselves when this table exists.  Use FreeType's metrics for
michael@0:     // other (including older PostScript) fonts.
michael@0:     if (mFace->underline_position && mFace->underline_thickness && yScale > 0.0) {
michael@0:         aMetrics->underlineSize = mFace->underline_thickness * yScale;
michael@0:         TT_Postscript *post = static_cast<TT_Postscript*>
michael@0:             (FT_Get_Sfnt_Table(mFace, ft_sfnt_post));
michael@0:         if (post && post->underlinePosition) {
michael@0:             aMetrics->underlineOffset = post->underlinePosition * yScale;
michael@0:         } else {
michael@0:             aMetrics->underlineOffset = mFace->underline_position * yScale
michael@0:                 + 0.5 * aMetrics->underlineSize;
michael@0:         }
michael@0:     } else { // No underline info.
michael@0:         // Imitate Pango.
michael@0:         aMetrics->underlineSize = emHeight / 14.0;
michael@0:         aMetrics->underlineOffset = -aMetrics->underlineSize;
michael@0:     }
michael@0: 
michael@0:     if (os2 && os2->yStrikeoutSize && os2->yStrikeoutPosition && yScale > 0.0) {
michael@0:         aMetrics->strikeoutSize = os2->yStrikeoutSize * yScale;
michael@0:         aMetrics->strikeoutOffset = os2->yStrikeoutPosition * yScale;
michael@0:     } else { // No strikeout info.
michael@0:         aMetrics->strikeoutSize = aMetrics->underlineSize;
michael@0:         // Use OpenType spec's suggested position for Roman font.
michael@0:         aMetrics->strikeoutOffset = emHeight * 409.0 / 2048.0
michael@0:             + 0.5 * aMetrics->strikeoutSize;
michael@0:     }
michael@0:     SnapLineToPixels(aMetrics->strikeoutOffset, aMetrics->strikeoutSize);
michael@0: 
michael@0:     if (os2 && os2->ySuperscriptYOffset) {
michael@0:         gfxFloat val = ScaleRoundDesignUnits(os2->ySuperscriptYOffset,
michael@0:                                              ftMetrics.y_scale);
michael@0:         aMetrics->superscriptOffset = std::max(1.0, val);
michael@0:     } else {
michael@0:         aMetrics->superscriptOffset = aMetrics->xHeight;
michael@0:     }
michael@0:     
michael@0:     if (os2 && os2->ySubscriptYOffset) {
michael@0:         gfxFloat val = ScaleRoundDesignUnits(os2->ySubscriptYOffset,
michael@0:                                              ftMetrics.y_scale);
michael@0:         // some fonts have the incorrect sign. 
michael@0:         val = fabs(val);
michael@0:         aMetrics->subscriptOffset = std::max(1.0, val);
michael@0:     } else {
michael@0:         aMetrics->subscriptOffset = aMetrics->xHeight;
michael@0:     }
michael@0: 
michael@0:     aMetrics->maxHeight = aMetrics->maxAscent + aMetrics->maxDescent;
michael@0: 
michael@0:     // Make the line height an integer number of pixels so that lines will be
michael@0:     // equally spaced (rather than just being snapped to pixels, some up and
michael@0:     // some down).  Layout calculates line height from the emHeight +
michael@0:     // internalLeading + externalLeading, but first each of these is rounded
michael@0:     // to layout units.  To ensure that the result is an integer number of
michael@0:     // pixels, round each of the components to pixels.
michael@0:     aMetrics->emHeight = floor(emHeight + 0.5);
michael@0: 
michael@0:     // maxHeight will normally be an integer, but round anyway in case
michael@0:     // FreeType is configured differently.
michael@0:     aMetrics->internalLeading =
michael@0:         floor(aMetrics->maxHeight - aMetrics->emHeight + 0.5);
michael@0: 
michael@0:     // Text input boxes currently don't work well with lineHeight
michael@0:     // significantly less than maxHeight (with Verdana, for example).
michael@0:     lineHeight = floor(std::max(lineHeight, aMetrics->maxHeight) + 0.5);
michael@0:     aMetrics->externalLeading =
michael@0:         lineHeight - aMetrics->internalLeading - aMetrics->emHeight;
michael@0: 
michael@0:     // Ensure emAscent + emDescent == emHeight
michael@0:     gfxFloat sum = aMetrics->emAscent + aMetrics->emDescent;
michael@0:     aMetrics->emAscent = sum > 0.0 ?
michael@0:         aMetrics->emAscent * aMetrics->emHeight / sum : 0.0;
michael@0:     aMetrics->emDescent = aMetrics->emHeight - aMetrics->emAscent;
michael@0: }
michael@0: 
michael@0: uint32_t
michael@0: gfxFT2LockedFace::GetGlyph(uint32_t aCharCode)
michael@0: {
michael@0:     if (MOZ_UNLIKELY(!mFace))
michael@0:         return 0;
michael@0: 
michael@0: #ifdef HAVE_FONTCONFIG_FCFREETYPE_H
michael@0:     // FcFreeTypeCharIndex will search starting from the most recently
michael@0:     // selected charmap.  This can cause non-determistic behavior when more
michael@0:     // than one charmap supports a character but with different glyphs, as
michael@0:     // with older versions of MS Gothic, for example.  Always prefer a Unicode
michael@0:     // charmap, if there is one.  (FcFreeTypeCharIndex usually does the
michael@0:     // appropriate Unicode conversion, but some fonts have non-Roman glyphs
michael@0:     // for FT_ENCODING_APPLE_ROMAN characters.)
michael@0:     if (!mFace->charmap || mFace->charmap->encoding != FT_ENCODING_UNICODE) {
michael@0:         FT_Select_Charmap(mFace, FT_ENCODING_UNICODE);
michael@0:     }
michael@0: 
michael@0:     return FcFreeTypeCharIndex(mFace, aCharCode);
michael@0: #else
michael@0:     return FT_Get_Char_Index(mFace, aCharCode);
michael@0: #endif
michael@0: }
michael@0: 
michael@0: typedef FT_UInt (*GetCharVariantFunction)(FT_Face  face,
michael@0:                                           FT_ULong charcode,
michael@0:                                           FT_ULong variantSelector);
michael@0: 
michael@0: uint32_t
michael@0: gfxFT2LockedFace::GetUVSGlyph(uint32_t aCharCode, uint32_t aVariantSelector)
michael@0: {
michael@0:     NS_PRECONDITION(aVariantSelector, "aVariantSelector should not be NULL");
michael@0: 
michael@0:     if (MOZ_UNLIKELY(!mFace))
michael@0:         return 0;
michael@0: 
michael@0:     // This function is available from FreeType 2.3.6 (June 2008).
michael@0:     static CharVariantFunction sGetCharVariantPtr = FindCharVariantFunction();
michael@0:     if (!sGetCharVariantPtr)
michael@0:         return 0;
michael@0: 
michael@0: #ifdef HAVE_FONTCONFIG_FCFREETYPE_H
michael@0:     // FcFreeTypeCharIndex may have changed the selected charmap.
michael@0:     // FT_Face_GetCharVariantIndex needs a unicode charmap.
michael@0:     if (!mFace->charmap || mFace->charmap->encoding != FT_ENCODING_UNICODE) {
michael@0:         FT_Select_Charmap(mFace, FT_ENCODING_UNICODE);
michael@0:     }
michael@0: #endif
michael@0: 
michael@0:     return (*sGetCharVariantPtr)(mFace, aCharCode, aVariantSelector);
michael@0: }
michael@0: 
michael@0: uint32_t
michael@0: gfxFT2LockedFace::GetCharExtents(char aChar, cairo_text_extents_t* aExtents)
michael@0: {
michael@0:     NS_PRECONDITION(aExtents != nullptr, "aExtents must not be NULL");
michael@0: 
michael@0:     if (!mFace)
michael@0:         return 0;
michael@0: 
michael@0:     FT_UInt gid = mGfxFont->GetGlyph(aChar);
michael@0:     if (gid) {
michael@0:         mGfxFont->GetGlyphExtents(gid, aExtents);
michael@0:     }
michael@0: 
michael@0:     return gid;
michael@0: }
michael@0: 
michael@0: gfxFT2LockedFace::CharVariantFunction
michael@0: gfxFT2LockedFace::FindCharVariantFunction()
michael@0: {
michael@0:     // This function is available from FreeType 2.3.6 (June 2008).
michael@0:     PRLibrary *lib = nullptr;
michael@0:     CharVariantFunction function =
michael@0:         reinterpret_cast<CharVariantFunction>
michael@0:         (PR_FindFunctionSymbolAndLibrary("FT_Face_GetCharVariantIndex", &lib));
michael@0:     if (!lib) {
michael@0:         return nullptr;
michael@0:     }
michael@0: 
michael@0:     FT_Int major;
michael@0:     FT_Int minor;
michael@0:     FT_Int patch;
michael@0:     FT_Library_Version(mFace->glyph->library, &major, &minor, &patch);
michael@0: 
michael@0:     // Versions 2.4.0 to 2.4.3 crash if configured with
michael@0:     // FT_CONFIG_OPTION_OLD_INTERNALS.  Presence of the symbol FT_Alloc
michael@0:     // indicates FT_CONFIG_OPTION_OLD_INTERNALS.
michael@0:     if (major == 2 && minor == 4 && patch < 4 &&
michael@0:         PR_FindFunctionSymbol(lib, "FT_Alloc")) {
michael@0:         function = nullptr;
michael@0:     }
michael@0: 
michael@0:     // Decrement the reference count incremented in
michael@0:     // PR_FindFunctionSymbolAndLibrary.
michael@0:     PR_UnloadLibrary(lib);
michael@0: 
michael@0:     return function;
michael@0: }