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stb_truetype: GPOS parsing fixes

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Glyphs not assigned a glyph class should default to class 0 as
per the OpenType spec. Also, change the code to treat malformed
data as an error to be handled, not an assert, and change the
way the version checking works.

Fixes the issue mentioned in PR #1035. Also, this part of the
code is indented incorrectly; will fix that in a subsequent
commit.
This commit is contained in:
Fabian Giesen 2021-07-07 02:58:28 -07:00
parent e590505492
commit 1252a3e641
1 changed files with 46 additions and 53 deletions
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37
stb_truetype.h
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@ -2479,12 +2479,13 @@ static stbtt_int32 stbtt__GetGlyphClass(stbtt_uint8 *classDefTable, int glyph)
} break; } break;
default: { default: {
// There are no other cases. // Unsupported defition type; return an error.
STBTT_assert(0); return -1;
} break; } break;
} }
return -1; // "All glyphs not assigned to a class fall into class 0". (OpenType spec)
return 0;
} }
// Define to STBTT_assert(x) if you want to break on unimplemented formats. // Define to STBTT_assert(x) if you want to break on unimplemented formats.
@ -2533,20 +2534,15 @@ static stbtt_int32 stbtt__GetGlyphGPOSInfoAdvance(const stbtt_fontinfo *info, i
int straw, needle; int straw, needle;
stbtt_uint16 valueFormat1 = ttUSHORT(table + 4); stbtt_uint16 valueFormat1 = ttUSHORT(table + 4);
stbtt_uint16 valueFormat2 = ttUSHORT(table + 6); stbtt_uint16 valueFormat2 = ttUSHORT(table + 6);
if (valueFormat1 == 4 && valueFormat2 == 0) { // Support more formats?
stbtt_int32 valueRecordPairSizeInBytes = 2; stbtt_int32 valueRecordPairSizeInBytes = 2;
stbtt_uint16 pairSetCount = ttUSHORT(table + 8); stbtt_uint16 pairSetCount = ttUSHORT(table + 8);
stbtt_uint16 pairPosOffset = ttUSHORT(table + 10 + 2 * coverageIndex); stbtt_uint16 pairPosOffset = ttUSHORT(table + 10 + 2 * coverageIndex);
stbtt_uint8 *pairValueTable = table + pairPosOffset; stbtt_uint8 *pairValueTable = table + pairPosOffset;
stbtt_uint16 pairValueCount = ttUSHORT(pairValueTable); stbtt_uint16 pairValueCount = ttUSHORT(pairValueTable);
stbtt_uint8 *pairValueArray = pairValueTable + 2; stbtt_uint8 *pairValueArray = pairValueTable + 2;
// TODO: Support more formats.
STBTT_GPOS_TODO_assert(valueFormat1 == 4);
if (valueFormat1 != 4) return 0;
STBTT_GPOS_TODO_assert(valueFormat2 == 0);
if (valueFormat2 != 0) return 0;
STBTT_assert(coverageIndex < pairSetCount); if (coverageIndex >= pairSetCount) return 0;
STBTT__NOTUSED(pairSetCount);
needle=glyph2; needle=glyph2;
r=pairValueCount-1; r=pairValueCount-1;
@ -2569,12 +2565,14 @@ static stbtt_int32 stbtt__GetGlyphGPOSInfoAdvance(const stbtt_fontinfo *info, i
return xAdvance; return xAdvance;
} }
} }
} else
return 0;
} break; } break;
case 2: { case 2: {
stbtt_uint16 valueFormat1 = ttUSHORT(table + 4); stbtt_uint16 valueFormat1 = ttUSHORT(table + 4);
stbtt_uint16 valueFormat2 = ttUSHORT(table + 6); stbtt_uint16 valueFormat2 = ttUSHORT(table + 6);
if (valueFormat1 == 4 && valueFormat2 == 0) { // Support more formats?
stbtt_uint16 classDef1Offset = ttUSHORT(table + 8); stbtt_uint16 classDef1Offset = ttUSHORT(table + 8);
stbtt_uint16 classDef2Offset = ttUSHORT(table + 10); stbtt_uint16 classDef2Offset = ttUSHORT(table + 10);
int glyph1class = stbtt__GetGlyphClass(table + classDef1Offset, glyph1); int glyph1class = stbtt__GetGlyphClass(table + classDef1Offset, glyph1);
@ -2582,26 +2580,21 @@ static stbtt_int32 stbtt__GetGlyphGPOSInfoAdvance(const stbtt_fontinfo *info, i
stbtt_uint16 class1Count = ttUSHORT(table + 12); stbtt_uint16 class1Count = ttUSHORT(table + 12);
stbtt_uint16 class2Count = ttUSHORT(table + 14); stbtt_uint16 class2Count = ttUSHORT(table + 14);
STBTT_assert(glyph1class < class1Count);
STBTT_assert(glyph2class < class2Count);
// TODO: Support more formats. if (glyph1class < 0 || glyph1class >= class1Count) return 0; // malformed
STBTT_GPOS_TODO_assert(valueFormat1 == 4); if (glyph2class < 0 || glyph2class >= class2Count) return 0; // malformed
if (valueFormat1 != 4) return 0;
STBTT_GPOS_TODO_assert(valueFormat2 == 0);
if (valueFormat2 != 0) return 0;
if (glyph1class >= 0 && glyph1class < class1Count && glyph2class >= 0 && glyph2class < class2Count) {
stbtt_uint8 *class1Records = table + 16; stbtt_uint8 *class1Records = table + 16;
stbtt_uint8 *class2Records = class1Records + 2 * (glyph1class * class2Count); stbtt_uint8 *class2Records = class1Records + 2 * (glyph1class * class2Count);
stbtt_int16 xAdvance = ttSHORT(class2Records + 2 * glyph2class); stbtt_int16 xAdvance = ttSHORT(class2Records + 2 * glyph2class);
return xAdvance; return xAdvance;
} } else
return 0;
} break; } break;
default: { default: {
// There are no other cases. // Unsupported definition type
STBTT_assert(0); return 0;
break; break;
}; };
} }