mirror of
https://github.com/daveallie/crosspoint-reader.git
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dc7544d944
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. ## Summary * **What is the goal of this PR?** (e.g., Fixes a bug in the user authentication module, Implements the new feature for file uploading.) Replace linear `O(n)` glyph lookup with binary search `O(log n)` to improve text rendering performance during page navigation. * **What changes are included?** - Modified `EpdFont::getGlyph()` to use binary search instead of linear search for unicode interval lookup - Added early return for empty interval count ## Additional Context * Add any other information that might be helpful for the reviewer (e.g., performance implications, potential risks, specific areas to focus on). - Performance implications: Fonts with many unicode intervals benefit the most. Korean fonts have ~30,000+ glyphs across multiple intervals, but any font with significant glyph coverage (CJK, extended Latin, emoji, etc.) will see improvement. - Complexity: from `O(n)` to `O(log n)` where n = number of unicode intervals. For fonts with 10+ intervals, this reduces lookup iterations significantly. - Risk: Low - the binary search logic is straightforward and the intervals are already sorted by unicode codepoint (required for the original early-exit optimization).
87 lines
2.2 KiB
C++
87 lines
2.2 KiB
C++
#include "EpdFont.h"
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#include <Utf8.h>
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inline int min(const int a, const int b) { return a < b ? a : b; }
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inline int max(const int a, const int b) { return a < b ? b : a; }
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void EpdFont::getTextBounds(const char* string, const int startX, const int startY, int* minX, int* minY, int* maxX,
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int* maxY) const {
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*minX = startX;
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*minY = startY;
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*maxX = startX;
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*maxY = startY;
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if (*string == '\0') {
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return;
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}
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int cursorX = startX;
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const int cursorY = startY;
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uint32_t cp;
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while ((cp = utf8NextCodepoint(reinterpret_cast<const uint8_t**>(&string)))) {
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const EpdGlyph* glyph = getGlyph(cp);
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if (!glyph) {
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// TODO: Replace with fallback glyph property?
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glyph = getGlyph('?');
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}
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if (!glyph) {
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// TODO: Better handle this?
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continue;
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}
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*minX = min(*minX, cursorX + glyph->left);
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*maxX = max(*maxX, cursorX + glyph->left + glyph->width);
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*minY = min(*minY, cursorY + glyph->top - glyph->height);
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*maxY = max(*maxY, cursorY + glyph->top);
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cursorX += glyph->advanceX;
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}
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}
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void EpdFont::getTextDimensions(const char* string, int* w, int* h) const {
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int minX = 0, minY = 0, maxX = 0, maxY = 0;
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getTextBounds(string, 0, 0, &minX, &minY, &maxX, &maxY);
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*w = maxX - minX;
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*h = maxY - minY;
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}
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bool EpdFont::hasPrintableChars(const char* string) const {
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int w = 0, h = 0;
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getTextDimensions(string, &w, &h);
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return w > 0 || h > 0;
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}
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const EpdGlyph* EpdFont::getGlyph(const uint32_t cp) const {
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const EpdUnicodeInterval* intervals = data->intervals;
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const int count = data->intervalCount;
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if (count == 0) return nullptr;
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// Binary search for O(log n) lookup instead of O(n)
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// Critical for Korean fonts with many unicode intervals
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int left = 0;
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int right = count - 1;
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while (left <= right) {
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const int mid = left + (right - left) / 2;
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const EpdUnicodeInterval* interval = &intervals[mid];
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if (cp < interval->first) {
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right = mid - 1;
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} else if (cp > interval->last) {
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left = mid + 1;
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} else {
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// Found: cp >= interval->first && cp <= interval->last
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return &data->glyph[interval->offset + (cp - interval->first)];
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}
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}
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return nullptr;
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}
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