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gfxHarfBuzzShaper.cpp
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gfxHarfBuzzShaper.cpp
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/* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* 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 "nsString.h"
#include "gfxContext.h"
#include "gfxFontConstants.h"
#include "gfxHarfBuzzShaper.h"
#include "gfxFontUtils.h"
#include "gfxTextRun.h"
#include "mozilla/Sprintf.h"
#include "nsUnicodeProperties.h"
#include "nsUnicodeScriptCodes.h"
#include "harfbuzz/hb.h"
#include "harfbuzz/hb-ot.h"
#include "unicode/unorm.h"
#include "unicode/utext.h"
static const UNormalizer2* sNormalizer = nullptr;
#include <algorithm>
#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
using namespace mozilla::unicode; // for Unicode property lookup
/*
* Creation and destruction; on deletion, release any font tables we're holding
*/
gfxHarfBuzzShaper::gfxHarfBuzzShaper(gfxFont* aFont)
: gfxFontShaper(aFont),
mHBFace(aFont->GetFontEntry()->GetHBFace()),
mHBFont(nullptr),
mBuffer(nullptr),
mCallbackData(),
mKernTable(nullptr),
mHmtxTable(nullptr),
mVmtxTable(nullptr),
mVORGTable(nullptr),
mLocaTable(nullptr),
mGlyfTable(nullptr),
mCmapTable(nullptr),
mCmapFormat(-1),
mSubtableOffset(0),
mUVSTableOffset(0),
mNumLongHMetrics(0),
mNumLongVMetrics(0),
mDefaultVOrg(-1.0),
mUseFontGetGlyph(aFont->ProvidesGetGlyph()),
mUseFontGlyphWidths(aFont->ProvidesGlyphWidths()),
mInitialized(false),
mVerticalInitialized(false),
mUseVerticalPresentationForms(false),
mLoadedLocaGlyf(false),
mLocaLongOffsets(false) {}
gfxHarfBuzzShaper::~gfxHarfBuzzShaper() {
// hb_*_destroy functions are safe to call on nullptr
hb_blob_destroy(mCmapTable);
hb_blob_destroy(mHmtxTable);
hb_blob_destroy(mKernTable);
hb_blob_destroy(mVmtxTable);
hb_blob_destroy(mVORGTable);
hb_blob_destroy(mLocaTable);
hb_blob_destroy(mGlyfTable);
hb_font_destroy(mHBFont);
hb_face_destroy(mHBFace);
hb_buffer_destroy(mBuffer);
}
#define UNICODE_BMP_LIMIT 0x10000
hb_codepoint_t gfxHarfBuzzShaper::GetNominalGlyph(
hb_codepoint_t unicode) const {
hb_codepoint_t gid = 0;
if (mUseFontGetGlyph) {
gid = mFont->GetGlyph(unicode, 0);
} else {
// we only instantiate a harfbuzz shaper if there's a cmap available
NS_ASSERTION(mFont->GetFontEntry()->HasCmapTable(),
"we cannot be using this font!");
NS_ASSERTION(mCmapTable && (mCmapFormat > 0) && (mSubtableOffset > 0),
"cmap data not correctly set up, expect disaster");
uint32_t length;
const uint8_t* data = (const uint8_t*)hb_blob_get_data(mCmapTable, &length);
switch (mCmapFormat) {
case 4:
gid =
unicode < UNICODE_BMP_LIMIT
? gfxFontUtils::MapCharToGlyphFormat4(
data + mSubtableOffset, length - mSubtableOffset, unicode)
: 0;
break;
case 10:
gid = gfxFontUtils::MapCharToGlyphFormat10(data + mSubtableOffset,
unicode);
break;
case 12:
case 13:
gid = gfxFontUtils::MapCharToGlyphFormat12or13(data + mSubtableOffset,
unicode);
break;
default:
NS_WARNING("unsupported cmap format, glyphs will be missing");
break;
}
}
if (!gid) {
// if there's no glyph for , just use the space glyph instead
if (unicode == 0xA0) {
gid = mFont->GetSpaceGlyph();
}
}
return gid;
}
hb_codepoint_t gfxHarfBuzzShaper::GetVariationGlyph(
hb_codepoint_t unicode, hb_codepoint_t variation_selector) const {
if (mUseFontGetGlyph) {
return mFont->GetGlyph(unicode, variation_selector);
}
NS_ASSERTION(mFont->GetFontEntry()->HasCmapTable(),
"we cannot be using this font!");
NS_ASSERTION(mCmapTable && (mCmapFormat > 0) && (mSubtableOffset > 0),
"cmap data not correctly set up, expect disaster");
uint32_t length;
const uint8_t* data = (const uint8_t*)hb_blob_get_data(mCmapTable, &length);
if (mUVSTableOffset) {
hb_codepoint_t gid = gfxFontUtils::MapUVSToGlyphFormat14(
data + mUVSTableOffset, unicode, variation_selector);
if (gid) {
return gid;
}
}
uint32_t compat = gfxFontUtils::GetUVSFallback(unicode, variation_selector);
if (compat) {
switch (mCmapFormat) {
case 4:
if (compat < UNICODE_BMP_LIMIT) {
return gfxFontUtils::MapCharToGlyphFormat4(
data + mSubtableOffset, length - mSubtableOffset, compat);
}
break;
case 10:
return gfxFontUtils::MapCharToGlyphFormat10(data + mSubtableOffset,
compat);
break;
case 12:
case 13:
return gfxFontUtils::MapCharToGlyphFormat12or13(data + mSubtableOffset,
compat);
break;
}
}
return 0;
}
static int VertFormsGlyphCompare(const void* aKey, const void* aElem) {
return int(*((hb_codepoint_t*)(aKey))) - int(*((uint16_t*)(aElem)));
}
// Return a vertical presentation-form codepoint corresponding to the
// given Unicode value, or 0 if no such form is available.
hb_codepoint_t gfxHarfBuzzShaper::GetVerticalPresentationForm(
hb_codepoint_t aUnicode) {
static const uint16_t sVerticalForms[][2] = {
{0x2013, 0xfe32}, // EN DASH
{0x2014, 0xfe31}, // EM DASH
{0x2025, 0xfe30}, // TWO DOT LEADER
{0x2026, 0xfe19}, // HORIZONTAL ELLIPSIS
{0x3001, 0xfe11}, // IDEOGRAPHIC COMMA
{0x3002, 0xfe12}, // IDEOGRAPHIC FULL STOP
{0x3008, 0xfe3f}, // LEFT ANGLE BRACKET
{0x3009, 0xfe40}, // RIGHT ANGLE BRACKET
{0x300a, 0xfe3d}, // LEFT DOUBLE ANGLE BRACKET
{0x300b, 0xfe3e}, // RIGHT DOUBLE ANGLE BRACKET
{0x300c, 0xfe41}, // LEFT CORNER BRACKET
{0x300d, 0xfe42}, // RIGHT CORNER BRACKET
{0x300e, 0xfe43}, // LEFT WHITE CORNER BRACKET
{0x300f, 0xfe44}, // RIGHT WHITE CORNER BRACKET
{0x3010, 0xfe3b}, // LEFT BLACK LENTICULAR BRACKET
{0x3011, 0xfe3c}, // RIGHT BLACK LENTICULAR BRACKET
{0x3014, 0xfe39}, // LEFT TORTOISE SHELL BRACKET
{0x3015, 0xfe3a}, // RIGHT TORTOISE SHELL BRACKET
{0x3016, 0xfe17}, // LEFT WHITE LENTICULAR BRACKET
{0x3017, 0xfe18}, // RIGHT WHITE LENTICULAR BRACKET
{0xfe4f, 0xfe34}, // WAVY LOW LINE
{0xff01, 0xfe15}, // FULLWIDTH EXCLAMATION MARK
{0xff08, 0xfe35}, // FULLWIDTH LEFT PARENTHESIS
{0xff09, 0xfe36}, // FULLWIDTH RIGHT PARENTHESIS
{0xff0c, 0xfe10}, // FULLWIDTH COMMA
{0xff1a, 0xfe13}, // FULLWIDTH COLON
{0xff1b, 0xfe14}, // FULLWIDTH SEMICOLON
{0xff1f, 0xfe16}, // FULLWIDTH QUESTION MARK
{0xff3b, 0xfe47}, // FULLWIDTH LEFT SQUARE BRACKET
{0xff3d, 0xfe48}, // FULLWIDTH RIGHT SQUARE BRACKET
{0xff3f, 0xfe33}, // FULLWIDTH LOW LINE
{0xff5b, 0xfe37}, // FULLWIDTH LEFT CURLY BRACKET
{0xff5d, 0xfe38} // FULLWIDTH RIGHT CURLY BRACKET
};
const uint16_t* charPair = static_cast<const uint16_t*>(
bsearch(&aUnicode, sVerticalForms, ArrayLength(sVerticalForms),
sizeof(sVerticalForms[0]), VertFormsGlyphCompare));
return charPair ? charPair[1] : 0;
}
static hb_bool_t HBGetNominalGlyph(hb_font_t* font, void* font_data,
hb_codepoint_t unicode,
hb_codepoint_t* glyph, void* user_data) {
const gfxHarfBuzzShaper::FontCallbackData* fcd =
static_cast<const gfxHarfBuzzShaper::FontCallbackData*>(font_data);
if (fcd->mShaper->UseVerticalPresentationForms()) {
hb_codepoint_t verticalForm =
gfxHarfBuzzShaper::GetVerticalPresentationForm(unicode);
if (verticalForm) {
*glyph = fcd->mShaper->GetNominalGlyph(verticalForm);
if (*glyph != 0) {
return true;
}
}
// fall back to the non-vertical form if we didn't find an alternate
}
*glyph = fcd->mShaper->GetNominalGlyph(unicode);
return *glyph != 0;
}
static hb_bool_t HBGetVariationGlyph(hb_font_t* font, void* font_data,
hb_codepoint_t unicode,
hb_codepoint_t variation_selector,
hb_codepoint_t* glyph, void* user_data) {
const gfxHarfBuzzShaper::FontCallbackData* fcd =
static_cast<const gfxHarfBuzzShaper::FontCallbackData*>(font_data);
if (fcd->mShaper->UseVerticalPresentationForms()) {
hb_codepoint_t verticalForm =
gfxHarfBuzzShaper::GetVerticalPresentationForm(unicode);
if (verticalForm) {
*glyph =
fcd->mShaper->GetVariationGlyph(verticalForm, variation_selector);
if (*glyph != 0) {
return true;
}
}
// fall back to the non-vertical form if we didn't find an alternate
}
*glyph = fcd->mShaper->GetVariationGlyph(unicode, variation_selector);
return *glyph != 0;
}
// Glyph metrics structures, shared (with appropriate reinterpretation of
// field names) by horizontal and vertical metrics tables.
struct LongMetric {
AutoSwap_PRUint16 advanceWidth; // or advanceHeight, when vertical
AutoSwap_PRInt16 lsb; // or tsb, when vertical
};
struct GlyphMetrics {
LongMetric metrics[1]; // actually numberOfLongMetrics
// the variable-length metrics[] array is immediately followed by:
// AutoSwap_PRUint16 leftSideBearing[];
};
hb_position_t gfxHarfBuzzShaper::GetGlyphHAdvance(hb_codepoint_t glyph) const {
// font did not implement GetGlyphWidth, so get an unhinted value
// directly from the font tables
NS_ASSERTION((mNumLongHMetrics > 0) && mHmtxTable != nullptr,
"font is lacking metrics, we shouldn't be here");
if (glyph >= uint32_t(mNumLongHMetrics)) {
glyph = mNumLongHMetrics - 1;
}
// glyph must be valid now, because we checked during initialization
// that mNumLongHMetrics is > 0, and that the metrics table is large enough
// to contain mNumLongHMetrics records
const ::GlyphMetrics* metrics = reinterpret_cast<const ::GlyphMetrics*>(
hb_blob_get_data(mHmtxTable, nullptr));
return FloatToFixed(mFont->FUnitsToDevUnitsFactor() *
uint16_t(metrics->metrics[glyph].advanceWidth));
}
hb_position_t gfxHarfBuzzShaper::GetGlyphVAdvance(hb_codepoint_t glyph) const {
if (!mVmtxTable) {
// Must be a "vertical" font that doesn't actually have vertical metrics;
// use a fixed advance.
return FloatToFixed(
mFont->GetMetrics(nsFontMetrics::eVertical).aveCharWidth);
}
NS_ASSERTION(mNumLongVMetrics > 0,
"font is lacking metrics, we shouldn't be here");
if (glyph >= uint32_t(mNumLongVMetrics)) {
glyph = mNumLongVMetrics - 1;
}
// glyph must be valid now, because we checked during initialization
// that mNumLongVMetrics is > 0, and that the metrics table is large enough
// to contain mNumLongVMetrics records
const ::GlyphMetrics* metrics = reinterpret_cast<const ::GlyphMetrics*>(
hb_blob_get_data(mVmtxTable, nullptr));
return FloatToFixed(mFont->FUnitsToDevUnitsFactor() *
uint16_t(metrics->metrics[glyph].advanceWidth));
}
/* static */
hb_position_t gfxHarfBuzzShaper::HBGetGlyphHAdvance(hb_font_t* font,
void* font_data,
hb_codepoint_t glyph,
void* user_data) {
const gfxHarfBuzzShaper::FontCallbackData* fcd =
static_cast<const gfxHarfBuzzShaper::FontCallbackData*>(font_data);
const gfxHarfBuzzShaper* shaper = fcd->mShaper;
if (shaper->mUseFontGlyphWidths) {
return shaper->GetFont()->GetGlyphWidth(glyph);
}
return shaper->GetGlyphHAdvance(glyph);
}
/* static */
hb_position_t gfxHarfBuzzShaper::HBGetGlyphVAdvance(hb_font_t* font,
void* font_data,
hb_codepoint_t glyph,
void* user_data) {
const gfxHarfBuzzShaper::FontCallbackData* fcd =
static_cast<const gfxHarfBuzzShaper::FontCallbackData*>(font_data);
// Currently, we don't offer gfxFont subclasses a method to override this
// and provide hinted platform-specific vertical advances (analogous to the
// GetGlyphWidth method for horizontal advances). If that proves necessary,
// we'll add a new gfxFont method and call it from here.
//
// We negate the value from GetGlyphVAdvance here because harfbuzz shapes
// with a coordinate system where positive is upwards, whereas the inline
// direction in which glyphs advance is downwards.
return -fcd->mShaper->GetGlyphVAdvance(glyph);
}
struct VORG {
AutoSwap_PRUint16 majorVersion;
AutoSwap_PRUint16 minorVersion;
AutoSwap_PRInt16 defaultVertOriginY;
AutoSwap_PRUint16 numVertOriginYMetrics;
};
struct VORGrec {
AutoSwap_PRUint16 glyphIndex;
AutoSwap_PRInt16 vertOriginY;
};
/* static */
hb_bool_t gfxHarfBuzzShaper::HBGetGlyphVOrigin(hb_font_t* font, void* font_data,
hb_codepoint_t glyph,
hb_position_t* x,
hb_position_t* y,
void* user_data) {
const gfxHarfBuzzShaper::FontCallbackData* fcd =
static_cast<const gfxHarfBuzzShaper::FontCallbackData*>(font_data);
fcd->mShaper->GetGlyphVOrigin(glyph, x, y);
return true;
}
void gfxHarfBuzzShaper::GetGlyphVOrigin(hb_codepoint_t aGlyph,
hb_position_t* aX,
hb_position_t* aY) const {
*aX = 0.5 * (mUseFontGlyphWidths ? mFont->GetGlyphWidth(aGlyph)
: GetGlyphHAdvance(aGlyph));
if (mVORGTable) {
// We checked in Initialize() that the VORG table is safely readable,
// so no length/bounds-check needed here.
const VORG* vorg =
reinterpret_cast<const VORG*>(hb_blob_get_data(mVORGTable, nullptr));
const VORGrec* lo = reinterpret_cast<const VORGrec*>(vorg + 1);
const VORGrec* hi = lo + uint16_t(vorg->numVertOriginYMetrics);
const VORGrec* limit = hi;
while (lo < hi) {
const VORGrec* mid = lo + (hi - lo) / 2;
if (uint16_t(mid->glyphIndex) < aGlyph) {
lo = mid + 1;
} else {
hi = mid;
}
}
if (lo < limit && uint16_t(lo->glyphIndex) == aGlyph) {
*aY = FloatToFixed(GetFont()->FUnitsToDevUnitsFactor() *
int16_t(lo->vertOriginY));
} else {
*aY = FloatToFixed(GetFont()->FUnitsToDevUnitsFactor() *
int16_t(vorg->defaultVertOriginY));
}
return;
}
if (mVmtxTable) {
bool emptyGlyf;
const Glyf* glyf = FindGlyf(aGlyph, &emptyGlyf);
if (glyf) {
if (emptyGlyf) {
*aY = 0;
return;
}
const ::GlyphMetrics* metrics = reinterpret_cast<const ::GlyphMetrics*>(
hb_blob_get_data(mVmtxTable, nullptr));
int16_t lsb;
if (aGlyph < hb_codepoint_t(mNumLongVMetrics)) {
// Glyph is covered by the first (advance & sidebearing) array
lsb = int16_t(metrics->metrics[aGlyph].lsb);
} else {
// Glyph is covered by the second (sidebearing-only) array
const AutoSwap_PRInt16* sidebearings =
reinterpret_cast<const AutoSwap_PRInt16*>(
&metrics->metrics[mNumLongVMetrics]);
lsb = int16_t(sidebearings[aGlyph - mNumLongVMetrics]);
}
*aY = FloatToFixed(mFont->FUnitsToDevUnitsFactor() *
(lsb + int16_t(glyf->yMax)));
return;
} else {
// XXX TODO: not a truetype font; need to get glyph extents
// via some other API?
// For now, fall through to default code below.
}
}
if (mDefaultVOrg < 0.0) {
// XXX should we consider using OS/2 sTypo* metrics if available?
gfxFontEntry::AutoTable hheaTable(GetFont()->GetFontEntry(),
TRUETYPE_TAG('h', 'h', 'e', 'a'));
if (hheaTable) {
uint32_t len;
const MetricsHeader* hhea = reinterpret_cast<const MetricsHeader*>(
hb_blob_get_data(hheaTable, &len));
if (len >= sizeof(MetricsHeader)) {
// divide up the default advance we're using (1em) in proportion
// to ascender:descender from the hhea table
int16_t a = int16_t(hhea->ascender);
int16_t d = int16_t(hhea->descender);
mDefaultVOrg = FloatToFixed(GetFont()->GetAdjustedSize() * a / (a - d));
}
}
if (mDefaultVOrg < 0.0) {
// Last resort, for non-sfnt fonts: get the horizontal metrics and
// compute a default VOrg from their ascent and descent.
const gfxFont::Metrics& mtx = mFont->GetHorizontalMetrics();
gfxFloat advance =
mFont->GetMetrics(nsFontMetrics::eVertical).aveCharWidth;
gfxFloat ascent = mtx.emAscent;
gfxFloat height = ascent + mtx.emDescent;
// vOrigin that will place the glyph so that its origin is shifted
// down most of the way within overall (vertical) advance, in
// proportion to the font ascent as a part of the overall font
// height.
mDefaultVOrg = FloatToFixed(advance * ascent / height);
}
}
*aY = mDefaultVOrg;
}
static hb_bool_t HBGetGlyphExtents(hb_font_t* font, void* font_data,
hb_codepoint_t glyph,
hb_glyph_extents_t* extents,
void* user_data) {
const gfxHarfBuzzShaper::FontCallbackData* fcd =
static_cast<const gfxHarfBuzzShaper::FontCallbackData*>(font_data);
return fcd->mShaper->GetGlyphExtents(glyph, extents);
}
// Find the data for glyph ID |aGlyph| in the 'glyf' table, if present.
// Returns null if not found, otherwise pointer to the beginning of the
// glyph's data. Sets aEmptyGlyf true if there is no actual data;
// otherwise, it's guaranteed that we can read at least the bounding box.
const gfxHarfBuzzShaper::Glyf* gfxHarfBuzzShaper::FindGlyf(
hb_codepoint_t aGlyph, bool* aEmptyGlyf) const {
if (!mLoadedLocaGlyf) {
mLoadedLocaGlyf = true; // only try this once; if it fails, this
// isn't a truetype font
gfxFontEntry* entry = mFont->GetFontEntry();
uint32_t len;
gfxFontEntry::AutoTable headTable(entry, TRUETYPE_TAG('h', 'e', 'a', 'd'));
if (!headTable) {
return nullptr;
}
const HeadTable* head =
reinterpret_cast<const HeadTable*>(hb_blob_get_data(headTable, &len));
if (len < sizeof(HeadTable)) {
return nullptr;
}
mLocaLongOffsets = int16_t(head->indexToLocFormat) > 0;
mLocaTable = entry->GetFontTable(TRUETYPE_TAG('l', 'o', 'c', 'a'));
mGlyfTable = entry->GetFontTable(TRUETYPE_TAG('g', 'l', 'y', 'f'));
}
if (!mLocaTable || !mGlyfTable) {
// it's not a truetype font
return nullptr;
}
uint32_t offset; // offset of glyph record in the 'glyf' table
uint32_t len;
const char* data = hb_blob_get_data(mLocaTable, &len);
if (mLocaLongOffsets) {
if ((aGlyph + 1) * sizeof(AutoSwap_PRUint32) > len) {
return nullptr;
}
const AutoSwap_PRUint32* offsets =
reinterpret_cast<const AutoSwap_PRUint32*>(data);
offset = offsets[aGlyph];
*aEmptyGlyf = (offset == uint16_t(offsets[aGlyph + 1]));
} else {
if ((aGlyph + 1) * sizeof(AutoSwap_PRUint16) > len) {
return nullptr;
}
const AutoSwap_PRUint16* offsets =
reinterpret_cast<const AutoSwap_PRUint16*>(data);
offset = uint16_t(offsets[aGlyph]);
*aEmptyGlyf = (offset == uint16_t(offsets[aGlyph + 1]));
offset *= 2;
}
data = hb_blob_get_data(mGlyfTable, &len);
if (offset + sizeof(Glyf) > len) {
return nullptr;
}
return reinterpret_cast<const Glyf*>(data + offset);
}
hb_bool_t gfxHarfBuzzShaper::GetGlyphExtents(
hb_codepoint_t aGlyph, hb_glyph_extents_t* aExtents) const {
bool emptyGlyf;
const Glyf* glyf = FindGlyf(aGlyph, &emptyGlyf);
if (!glyf) {
// TODO: for non-truetype fonts, get extents some other way?
return false;
}
if (emptyGlyf) {
aExtents->x_bearing = 0;
aExtents->y_bearing = 0;
aExtents->width = 0;
aExtents->height = 0;
return true;
}
double f = mFont->FUnitsToDevUnitsFactor();
aExtents->x_bearing = FloatToFixed(int16_t(glyf->xMin) * f);
aExtents->width =
FloatToFixed((int16_t(glyf->xMax) - int16_t(glyf->xMin)) * f);
// Our y-coordinates are positive-downwards, whereas harfbuzz assumes
// positive-upwards; hence the apparently-reversed subtractions here.
aExtents->y_bearing = FloatToFixed(int16_t(glyf->yMax) * f -
mFont->GetHorizontalMetrics().emAscent);
aExtents->height =
FloatToFixed((int16_t(glyf->yMin) - int16_t(glyf->yMax)) * f);
return true;
}
static hb_bool_t HBGetContourPoint(hb_font_t* font, void* font_data,
unsigned int point_index,
hb_codepoint_t glyph, hb_position_t* x,
hb_position_t* y, void* user_data) {
/* not yet implemented - no support for used of hinted contour points
to fine-tune anchor positions in GPOS AnchorFormat2 */
return false;
}
struct KernHeaderFmt0 {
AutoSwap_PRUint16 nPairs;
AutoSwap_PRUint16 searchRange;
AutoSwap_PRUint16 entrySelector;
AutoSwap_PRUint16 rangeShift;
};
struct KernPair {
AutoSwap_PRUint16 left;
AutoSwap_PRUint16 right;
AutoSwap_PRInt16 value;
};
// Find a kern pair in a Format 0 subtable.
// The aSubtable parameter points to the subtable itself, NOT its header,
// as the header structure differs between Windows and Mac (v0 and v1.0)
// versions of the 'kern' table.
// aSubtableLen is the length of the subtable EXCLUDING its header.
// If the pair <aFirstGlyph,aSecondGlyph> is found, the kerning value is
// added to aValue, so that multiple subtables can accumulate a total
// kerning value for a given pair.
static void GetKernValueFmt0(const void* aSubtable, uint32_t aSubtableLen,
uint16_t aFirstGlyph, uint16_t aSecondGlyph,
int32_t& aValue, bool aIsOverride = false,
bool aIsMinimum = false) {
const KernHeaderFmt0* hdr =
reinterpret_cast<const KernHeaderFmt0*>(aSubtable);
const KernPair* lo = reinterpret_cast<const KernPair*>(hdr + 1);
const KernPair* hi = lo + uint16_t(hdr->nPairs);
const KernPair* limit = hi;
if (reinterpret_cast<const char*>(aSubtable) + aSubtableLen <
reinterpret_cast<const char*>(hi)) {
// subtable is not large enough to contain the claimed number
// of kern pairs, so just ignore it
return;
}
#define KERN_PAIR_KEY(l, r) (uint32_t((uint16_t(l) << 16) + uint16_t(r)))
uint32_t key = KERN_PAIR_KEY(aFirstGlyph, aSecondGlyph);
while (lo < hi) {
const KernPair* mid = lo + (hi - lo) / 2;
if (KERN_PAIR_KEY(mid->left, mid->right) < key) {
lo = mid + 1;
} else {
hi = mid;
}
}
if (lo < limit && KERN_PAIR_KEY(lo->left, lo->right) == key) {
if (aIsOverride) {
aValue = int16_t(lo->value);
} else if (aIsMinimum) {
aValue = std::max(aValue, int32_t(lo->value));
} else {
aValue += int16_t(lo->value);
}
}
}
// Get kerning value from Apple (version 1.0) kern table,
// subtable format 2 (simple N x M array of kerning values)
// See http://developer.apple.com/fonts/TTRefMan/RM06/Chap6kern.html
// for details of version 1.0 format 2 subtable.
struct KernHeaderVersion1Fmt2 {
KernTableSubtableHeaderVersion1 header;
AutoSwap_PRUint16 rowWidth;
AutoSwap_PRUint16 leftOffsetTable;
AutoSwap_PRUint16 rightOffsetTable;
AutoSwap_PRUint16 array;
};
struct KernClassTableHdr {
AutoSwap_PRUint16 firstGlyph;
AutoSwap_PRUint16 nGlyphs;
AutoSwap_PRUint16 offsets[1]; // actually an array of nGlyphs entries
};
static int16_t GetKernValueVersion1Fmt2(const void* aSubtable,
uint32_t aSubtableLen,
uint16_t aFirstGlyph,
uint16_t aSecondGlyph) {
if (aSubtableLen < sizeof(KernHeaderVersion1Fmt2)) {
return 0;
}
const char* base = reinterpret_cast<const char*>(aSubtable);
const char* subtableEnd = base + aSubtableLen;
const KernHeaderVersion1Fmt2* h =
reinterpret_cast<const KernHeaderVersion1Fmt2*>(aSubtable);
uint32_t offset = h->array;
const KernClassTableHdr* leftClassTable =
reinterpret_cast<const KernClassTableHdr*>(base +
uint16_t(h->leftOffsetTable));
if (reinterpret_cast<const char*>(leftClassTable) +
sizeof(KernClassTableHdr) >
subtableEnd) {
return 0;
}
if (aFirstGlyph >= uint16_t(leftClassTable->firstGlyph)) {
aFirstGlyph -= uint16_t(leftClassTable->firstGlyph);
if (aFirstGlyph < uint16_t(leftClassTable->nGlyphs)) {
if (reinterpret_cast<const char*>(leftClassTable) +
sizeof(KernClassTableHdr) + aFirstGlyph * sizeof(uint16_t) >=
subtableEnd) {
return 0;
}
offset = uint16_t(leftClassTable->offsets[aFirstGlyph]);
}
}
const KernClassTableHdr* rightClassTable =
reinterpret_cast<const KernClassTableHdr*>(base +
uint16_t(h->rightOffsetTable));
if (reinterpret_cast<const char*>(rightClassTable) +
sizeof(KernClassTableHdr) >
subtableEnd) {
return 0;
}
if (aSecondGlyph >= uint16_t(rightClassTable->firstGlyph)) {
aSecondGlyph -= uint16_t(rightClassTable->firstGlyph);
if (aSecondGlyph < uint16_t(rightClassTable->nGlyphs)) {
if (reinterpret_cast<const char*>(rightClassTable) +
sizeof(KernClassTableHdr) + aSecondGlyph * sizeof(uint16_t) >=
subtableEnd) {
return 0;
}
offset += uint16_t(rightClassTable->offsets[aSecondGlyph]);
}
}
const AutoSwap_PRInt16* pval =
reinterpret_cast<const AutoSwap_PRInt16*>(base + offset);
if (reinterpret_cast<const char*>(pval + 1) >= subtableEnd) {
return 0;
}
return *pval;
}
// Get kerning value from Apple (version 1.0) kern table,
// subtable format 3 (simple N x M array of kerning values)
// See http://developer.apple.com/fonts/TTRefMan/RM06/Chap6kern.html
// for details of version 1.0 format 3 subtable.
struct KernHeaderVersion1Fmt3 {
KernTableSubtableHeaderVersion1 header;
AutoSwap_PRUint16 glyphCount;
uint8_t kernValueCount;
uint8_t leftClassCount;
uint8_t rightClassCount;
uint8_t flags;
};
static int16_t GetKernValueVersion1Fmt3(const void* aSubtable,
uint32_t aSubtableLen,
uint16_t aFirstGlyph,
uint16_t aSecondGlyph) {
// check that we can safely read the header fields
if (aSubtableLen < sizeof(KernHeaderVersion1Fmt3)) {
return 0;
}
const KernHeaderVersion1Fmt3* hdr =
reinterpret_cast<const KernHeaderVersion1Fmt3*>(aSubtable);
if (hdr->flags != 0) {
return 0;
}
uint16_t glyphCount = hdr->glyphCount;
// check that table is large enough for the arrays
if (sizeof(KernHeaderVersion1Fmt3) + hdr->kernValueCount * sizeof(int16_t) +
glyphCount + glyphCount + hdr->leftClassCount * hdr->rightClassCount >
aSubtableLen) {
return 0;
}
if (aFirstGlyph >= glyphCount || aSecondGlyph >= glyphCount) {
// glyphs are out of range for the class tables
return 0;
}
// get pointers to the four arrays within the subtable
const AutoSwap_PRInt16* kernValue =
reinterpret_cast<const AutoSwap_PRInt16*>(hdr + 1);
const uint8_t* leftClass =
reinterpret_cast<const uint8_t*>(kernValue + hdr->kernValueCount);
const uint8_t* rightClass = leftClass + glyphCount;
const uint8_t* kernIndex = rightClass + glyphCount;
uint8_t lc = leftClass[aFirstGlyph];
uint8_t rc = rightClass[aSecondGlyph];
if (lc >= hdr->leftClassCount || rc >= hdr->rightClassCount) {
return 0;
}
uint8_t ki = kernIndex[leftClass[aFirstGlyph] * hdr->rightClassCount +
rightClass[aSecondGlyph]];
if (ki >= hdr->kernValueCount) {
return 0;
}
return kernValue[ki];
}
#define KERN0_COVERAGE_HORIZONTAL 0x0001
#define KERN0_COVERAGE_MINIMUM 0x0002
#define KERN0_COVERAGE_CROSS_STREAM 0x0004
#define KERN0_COVERAGE_OVERRIDE 0x0008
#define KERN0_COVERAGE_RESERVED 0x00F0
#define KERN1_COVERAGE_VERTICAL 0x8000
#define KERN1_COVERAGE_CROSS_STREAM 0x4000
#define KERN1_COVERAGE_VARIATION 0x2000
#define KERN1_COVERAGE_RESERVED 0x1F00
hb_position_t gfxHarfBuzzShaper::GetHKerning(uint16_t aFirstGlyph,
uint16_t aSecondGlyph) const {
// We want to ignore any kern pairs involving <space>, because we are
// handling words in isolation, the only space characters seen here are
// the ones artificially added by the textRun code.
uint32_t spaceGlyph = mFont->GetSpaceGlyph();
if (aFirstGlyph == spaceGlyph || aSecondGlyph == spaceGlyph) {
return 0;
}
if (!mKernTable) {
mKernTable =
mFont->GetFontEntry()->GetFontTable(TRUETYPE_TAG('k', 'e', 'r', 'n'));
if (!mKernTable) {
mKernTable = hb_blob_get_empty();
}
}
uint32_t len;
const char* base = hb_blob_get_data(mKernTable, &len);
if (len < sizeof(KernTableVersion0)) {
return 0;
}
int32_t value = 0;
// First try to interpret as "version 0" kern table
// (see http://www.microsoft.com/typography/otspec/kern.htm)
const KernTableVersion0* kern0 =
reinterpret_cast<const KernTableVersion0*>(base);
if (uint16_t(kern0->version) == 0) {
uint16_t nTables = kern0->nTables;
uint32_t offs = sizeof(KernTableVersion0);
for (uint16_t i = 0; i < nTables; ++i) {
if (offs + sizeof(KernTableSubtableHeaderVersion0) > len) {
break;
}
const KernTableSubtableHeaderVersion0* st0 =
reinterpret_cast<const KernTableSubtableHeaderVersion0*>(base + offs);
uint16_t subtableLen = uint16_t(st0->length);
if (offs + subtableLen > len) {
break;
}
offs += subtableLen;
uint16_t coverage = st0->coverage;
if (!(coverage & KERN0_COVERAGE_HORIZONTAL)) {
// we only care about horizontal kerning (for now)
continue;
}
if (coverage & (KERN0_COVERAGE_CROSS_STREAM | KERN0_COVERAGE_RESERVED)) {
// we don't support cross-stream kerning, and
// reserved bits should be zero;
// ignore the subtable if not
continue;
}
uint8_t format = (coverage >> 8);
switch (format) {
case 0:
GetKernValueFmt0(st0 + 1, subtableLen - sizeof(*st0), aFirstGlyph,
aSecondGlyph, value,
(coverage & KERN0_COVERAGE_OVERRIDE) != 0,
(coverage & KERN0_COVERAGE_MINIMUM) != 0);
break;
default:
// TODO: implement support for other formats,
// if they're ever used in practice
#if DEBUG
{
char buf[1024];
SprintfLiteral(buf,
"unknown kern subtable in %s: "
"ver 0 format %d\n",
mFont->GetName().get(), format);
NS_WARNING(buf);
}
#endif
break;
}
}
} else {
// It wasn't a "version 0" table; check if it is Apple version 1.0
// (see http://developer.apple.com/fonts/TTRefMan/RM06/Chap6kern.html)
const KernTableVersion1* kern1 =
reinterpret_cast<const KernTableVersion1*>(base);
if (uint32_t(kern1->version) == 0x00010000) {
uint32_t nTables = kern1->nTables;
uint32_t offs = sizeof(KernTableVersion1);
for (uint32_t i = 0; i < nTables; ++i) {
if (offs + sizeof(KernTableSubtableHeaderVersion1) > len) {
break;
}
const KernTableSubtableHeaderVersion1* st1 =
reinterpret_cast<const KernTableSubtableHeaderVersion1*>(base +
offs);
uint32_t subtableLen = uint32_t(st1->length);
offs += subtableLen;
uint16_t coverage = st1->coverage;
if (coverage & (KERN1_COVERAGE_VERTICAL | KERN1_COVERAGE_CROSS_STREAM |
KERN1_COVERAGE_VARIATION | KERN1_COVERAGE_RESERVED)) {
// we only care about horizontal kerning (for now),
// we don't support cross-stream kerning,
// we don't support variations,
// reserved bits should be zero;
// ignore the subtable if not
continue;
}
uint8_t format = (coverage & 0xff);
switch (format) {
case 0:
GetKernValueFmt0(st1 + 1, subtableLen - sizeof(*st1), aFirstGlyph,
aSecondGlyph, value);
break;
case 2:
value = GetKernValueVersion1Fmt2(st1, subtableLen, aFirstGlyph,
aSecondGlyph);
break;
case 3:
value = GetKernValueVersion1Fmt3(st1, subtableLen, aFirstGlyph,
aSecondGlyph);
break;
default:
// TODO: implement support for other formats.
// Note that format 1 cannot be supported here,
// as it requires the full glyph array to run the FSM,
// not just the current glyph pair.
#if DEBUG
{
char buf[1024];
SprintfLiteral(buf,
"unknown kern subtable in %s: "
"ver 0 format %d\n",
mFont->GetName().get(), format);
NS_WARNING(buf);
}
#endif
break;
}
}
}
}
if (value != 0) {
return FloatToFixed(mFont->FUnitsToDevUnitsFactor() * value);
}
return 0;
}
static hb_position_t HBGetHKerning(hb_font_t* font, void* font_data,
hb_codepoint_t first_glyph,
hb_codepoint_t second_glyph,
void* user_data) {
const gfxHarfBuzzShaper::FontCallbackData* fcd =
static_cast<const gfxHarfBuzzShaper::FontCallbackData*>(font_data);
return fcd->mShaper->GetHKerning(first_glyph, second_glyph);
}
/*
* HarfBuzz unicode property callbacks
*/
static hb_codepoint_t HBGetMirroring(hb_unicode_funcs_t* ufuncs,
hb_codepoint_t aCh, void* user_data) {
return GetMirroredChar(aCh);
}
static hb_unicode_general_category_t HBGetGeneralCategory(
hb_unicode_funcs_t* ufuncs, hb_codepoint_t aCh, void* user_data) {
return hb_unicode_general_category_t(GetGeneralCategory(aCh));
}
static hb_script_t HBGetScript(hb_unicode_funcs_t* ufuncs, hb_codepoint_t aCh,
void* user_data) {
return hb_script_t(GetScriptTagForCode(GetScriptCode(aCh)));
}
static hb_unicode_combining_class_t HBGetCombiningClass(
hb_unicode_funcs_t* ufuncs, hb_codepoint_t aCh, void* user_data) {
return hb_unicode_combining_class_t(GetCombiningClass(aCh));