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Optimize glyph lookup with binary search for Korean fonts

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Replace linear O(n) search with binary search O(log n) for unicode
interval lookup. Korean fonts have many intervals (~30,000+ glyphs),
so this improves text rendering performance during page navigation.
This commit is contained in:
Eunchurn Park 2025-12-25 15:25:36 +09:00
parent 504c7b307d
commit 129cd2bc48
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GPG Key ID: 29D94D9C697E3F92
1 changed files with 20 additions and 6 deletions
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26
lib/EpdFont/EpdFont.cpp
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@ -59,14 +59,28 @@ bool EpdFont::hasPrintableChars(const char* string) const {
const EpdGlyph* EpdFont::getGlyph(const uint32_t cp) const {
const EpdUnicodeInterval* intervals = data->intervals;
for (int i = 0; i < data->intervalCount; i++) {
const EpdUnicodeInterval* interval = &intervals[i];
if (cp >= interval->first && cp <= interval->last) {
const int count = data->intervalCount;
if (count == 0) return nullptr;
// Binary search for O(log n) lookup instead of O(n)
// Critical for Korean fonts with many unicode intervals
int left = 0;
int right = count - 1;
while (left <= right) {
const int mid = left + (right - left) / 2;
const EpdUnicodeInterval* interval = &intervals[mid];
if (cp < interval->first) {
right = mid - 1;
} else if (cp > interval->last) {
left = mid + 1;
} else {
// Found: cp >= interval->first && cp <= interval->last
return &data->glyph[interval->offset + (cp - interval->first)];
}
if (cp < interval->first) {
return nullptr;
}
}
return nullptr;
}