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/* 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 "gfxMathTable.h"
#include "harfbuzz/hb.h"
#include "harfbuzz/hb-ot.h"
#define FixedToFloat(f) ((f) * (1.0 / 65536.0))
using namespace mozilla;
gfxMathTable::gfxMathTable(hb_face_t *aFace, gfxFloat aSize)
{
mHBFont = hb_font_create(aFace);
if (mHBFont) {
hb_font_set_ppem(mHBFont, aSize, aSize);
uint32_t scale = FloatToFixed(aSize);
hb_font_set_scale(mHBFont, scale, scale);
}
mMathVariantCache.glyphID = 0;
ClearCache();
}
gfxMathTable::~gfxMathTable()
{
if (mHBFont) {
hb_font_destroy(mHBFont);
}
}
gfxFloat
gfxMathTable::Constant(MathConstant aConstant) const
{
int32_t value = hb_ot_math_get_constant(mHBFont, static_cast<hb_ot_math_constant_t>(aConstant));
if (aConstant == ScriptPercentScaleDown ||
aConstant == ScriptScriptPercentScaleDown ||
aConstant == RadicalDegreeBottomRaisePercent) {
return value / 100.0;
}
return FixedToFloat(value);
}
gfxFloat
gfxMathTable::ItalicsCorrection(uint32_t aGlyphID) const
{
return FixedToFloat(hb_ot_math_get_glyph_italics_correction(mHBFont, aGlyphID));
}
uint32_t
gfxMathTable::VariantsSize(uint32_t aGlyphID, bool aVertical,
uint16_t aSize) const
{
UpdateMathVariantCache(aGlyphID, aVertical);
if (aSize < kMaxCachedSizeCount) {
return mMathVariantCache.sizes[aSize];
}
// If the size index exceeds the cache size, we just read the value with
// hb_ot_math_get_glyph_variants.
hb_direction_t direction = aVertical ? HB_DIRECTION_BTT : HB_DIRECTION_LTR;
hb_ot_math_glyph_variant_t variant;
unsigned int count = 1;
hb_ot_math_get_glyph_variants(mHBFont, aGlyphID, direction, aSize, &count,
&variant);
return count > 0 ? variant.glyph : 0;
}
bool
gfxMathTable::VariantsParts(uint32_t aGlyphID, bool aVertical,
uint32_t aGlyphs[4]) const
{
UpdateMathVariantCache(aGlyphID, aVertical);
memcpy(aGlyphs, mMathVariantCache.parts, sizeof(mMathVariantCache.parts));
return mMathVariantCache.arePartsValid;
}
void
gfxMathTable::ClearCache() const
{
memset(mMathVariantCache.sizes, 0, sizeof(mMathVariantCache.sizes));
memset(mMathVariantCache.parts, 0, sizeof(mMathVariantCache.parts));
mMathVariantCache.arePartsValid = false;
}
void
gfxMathTable::UpdateMathVariantCache(uint32_t aGlyphID, bool aVertical) const
{
if (aGlyphID == mMathVariantCache.glyphID &&
aVertical == mMathVariantCache.vertical)
return;
mMathVariantCache.glyphID = aGlyphID;
mMathVariantCache.vertical = aVertical;
ClearCache();
// Cache the first size variants.
hb_direction_t direction = aVertical ? HB_DIRECTION_BTT : HB_DIRECTION_LTR;
hb_ot_math_glyph_variant_t variant[kMaxCachedSizeCount];
unsigned int count = kMaxCachedSizeCount;
hb_ot_math_get_glyph_variants(mHBFont, aGlyphID, direction, 0, &count,
variant);
for (unsigned int i = 0; i < count; i++) {
mMathVariantCache.sizes[i] = variant[i].glyph;
}
// Try and cache the parts of the glyph assembly.
// XXXfredw The structure of the Open Type Math table is a bit more general
// than the one currently used by the nsMathMLChar code, so we try to fallback
// in reasonable way. We use the approach of the copyComponents function in
// github.com/mathjax/MathJax-dev/blob/master/fonts/OpenTypeMath/fontUtil.py
//
// The nsMathMLChar code can use at most 3 non extender pieces (aGlyphs[0],
// aGlyphs[1] and aGlyphs[2]) and the extenders between these pieces should
// all be the same (aGlyphs[4]). Also, the parts of vertical assembly are
// stored from bottom to top in the Open Type MATH table while they are
// stored from top to bottom in nsMathMLChar.
hb_ot_math_glyph_part_t parts[5];
count = MOZ_ARRAY_LENGTH(parts);
unsigned int offset = 0;
if (hb_ot_math_get_glyph_assembly(mHBFont, aGlyphID, direction, offset, &count, parts, NULL) > MOZ_ARRAY_LENGTH(parts))
return; // Not supported: Too many pieces.
if (count <= 0)
return; // Not supported: No pieces.
// Count the number of non extender pieces
uint16_t nonExtenderCount = 0;
for (uint16_t i = 0; i < count; i++) {
if (!(parts[i].flags & HB_MATH_GLYPH_PART_FLAG_EXTENDER)) {
nonExtenderCount++;
}
}
if (nonExtenderCount > 3) {
// Not supported: too many pieces
return;
}
// Now browse the list of pieces
// 0 = look for a left/bottom glyph
// 1 = look for an extender between left/bottom and mid
// 2 = look for a middle glyph
// 3 = look for an extender between middle and right/top
// 4 = look for a right/top glyph
// 5 = no more piece expected
uint8_t state = 0;
// First extender char found.
uint32_t extenderChar = 0;
for (uint16_t i = 0; i < count; i++) {
bool isExtender = parts[i].flags & HB_MATH_GLYPH_PART_FLAG_EXTENDER;
uint32_t glyph = parts[i].glyph;
if ((state == 1 || state == 2) && nonExtenderCount < 3) {
// do not try to find a middle glyph
state += 2;
}
if (isExtender) {
if (!extenderChar) {
extenderChar = glyph;
mMathVariantCache.parts[3] = extenderChar;
} else if (extenderChar != glyph) {
// Not supported: different extenders
return;
}
if (state == 0) { // or state == 1
// ignore left/bottom piece and multiple successive extenders
state = 1;
} else if (state == 2) { // or state == 3
// ignore middle piece and multiple successive extenders
state = 3;
} else if (state >= 4) {
// Not supported: unexpected extender
return;
}
continue;
}
if (state == 0) {
// copy left/bottom part
mMathVariantCache.parts[aVertical ? 2 : 0] = glyph;
state = 1;
continue;
}
if (state == 1 || state == 2) {
// copy middle part
mMathVariantCache.parts[1] = glyph;
state = 3;
continue;
}
if (state == 3 || state == 4) {
// copy right/top part
mMathVariantCache.parts[aVertical ? 0 : 2] = glyph;
state = 5;
}
}
mMathVariantCache.arePartsValid = true;
}
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