Fix #11827: Make Layouter::GetCharPosition() aware of ligatures. (#11831)

When ligatures happen the precise individual character position is not known, so instead return the previous position (which is that of the ligature.)
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Peter Nelson 2024-01-20 17:16:42 +00:00 committed by GitHub
parent 086cbd0d72
commit d6ccfdbbd9
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1 changed files with 20 additions and 9 deletions

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@ -244,10 +244,12 @@ Point Layouter::GetCharPosition(std::string_view::const_iterator ch) const
if (!IsConsumedFormattingCode(c)) index += line->GetInternalCharLength(c);
}
/* Initial position, returned if character not found. */
static const std::vector<Point> zero = { {0, 0} };
auto position = zero.begin();
/* We couldn't find the code point index. */
if (str != ch) {
return { 0, 0 };
}
if (str != ch) return *position;
/* Valid character. */
@ -257,15 +259,24 @@ Point Layouter::GetCharPosition(std::string_view::const_iterator ch) const
const auto &positions = run.GetPositions();
const auto &charmap = run.GetGlyphToCharMap();
for (int i = 0; i < run.GetGlyphCount(); i++) {
/* Matching glyph? Return position. */
if ((size_t)charmap[i] == index) {
return positions[i];
}
/* Run starts after our character, use the last found position. */
if ((size_t)charmap.front() > index) return *position;
position = positions.begin();
for (auto it = charmap.begin(); it != charmap.end(); /* nothing */) {
/* Plain honest-to-$deity match. */
if ((size_t)*it == index) return *position;
++it;
if (it == charmap.end()) break;
/* We just passed our character, it's probably a ligature, use the last found position. */
if ((size_t)*it > index) return *position;
++position;
}
}
NOT_REACHED();
/* At the end of the run but still didn't find our character so probably a trailing ligature, use the last found position. */
return *position;
}
/**