fix: Fix hyphenation and rendering of decomposed characters (#1037)

## Summary

* This PR fixes decomposed diacritic handling end-to-end:
- Hyphenation: normalize common Latin base+combining sequences to
precomposed codepoints before Liang pattern matching, so decomposed
words hyphenate correctly
- Rendering: correct combining-mark placement logic so non-spacing marks
are attached to the preceding base glyph in normal and rotated text
rendering paths, with corresponding text-bounds consistency updates.
- Hyphenation around non breaking space variants have been fixed (and
extended)
- Hyphenation of terms that already included of hyphens were fixed to
include Liang pattern application (eg "US-Satellitensystem" was
*exclusively* broken at the existing hyphen)

## Additional Context

* Before
<img width="800" height="480" alt="2"
src="https://github.com/user-attachments/assets/b9c515c4-ab75-45cc-8b52-f4d86bce519d"
/>


* After
<img width="480" height="800" alt="fix1"
src="https://github.com/user-attachments/assets/4999f6a8-f51c-4c0a-b144-f153f77ddb57"
/>
<img width="800" height="480" alt="fix2"
src="https://github.com/user-attachments/assets/7355126b-80c7-441f-b390-4e0897ee3fb6"
/>

* Note 1: the hyphenation fix is not a 100% bullet proof implementation.
It adds composition of *common* base+combining sequences (e.g. O +
U+0308 -> Ö) during codepoint collection. A complete solution would
require implementing proper Unicode normalization (at least NFC,
possibly NFKC in specific cases) before hyphenation and rendering,
instead of hand-mapping a few combining marks. That was beyond the scope
of this fix.

* Note 2: the render fix should be universal and not limited to the
constraints outlined above: it properly x-centers the compund glyph over
the previous one, and it uses at least 1pt of visual distance in y.

Before:
<img width="478" height="167" alt="Image"
src="https://github.com/user-attachments/assets/f8db60d5-35b1-4477-96d0-5003b4e4a2a1"
/>

After: 
<img width="479" height="180" alt="Image"
src="https://github.com/user-attachments/assets/1b48ef97-3a77-475a-8522-23f4aca8e904"
/>

* This should resolve the issues described in #998 
---

### AI Usage

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please be transparent about their usage as it
helps set the right context for reviewers.

Did you use AI tools to help write this code? _**PARTIALLY**_
This commit is contained in:
jpirnay
2026-02-22 03:11:07 +01:00
committed by GitHub
parent 10a2678584
commit 5f5561b684
8 changed files with 459 additions and 29 deletions

View File

@@ -17,6 +17,11 @@ void EpdFont::getTextBounds(const char* string, const int startX, const int star
int cursorX = startX;
const int cursorY = startY;
int lastBaseX = startX;
int lastBaseAdvance = 0;
int lastBaseTop = 0;
bool hasBaseGlyph = false;
constexpr int MIN_COMBINING_GAP_PX = 1;
uint32_t cp;
while ((cp = utf8NextCodepoint(reinterpret_cast<const uint8_t**>(&string)))) {
const EpdGlyph* glyph = getGlyph(cp);
@@ -30,11 +35,30 @@ void EpdFont::getTextBounds(const char* string, const int startX, const int star
continue;
}
*minX = std::min(*minX, cursorX + glyph->left);
*maxX = std::max(*maxX, cursorX + glyph->left + glyph->width);
*minY = std::min(*minY, cursorY + glyph->top - glyph->height);
*maxY = std::max(*maxY, cursorY + glyph->top);
cursorX += glyph->advanceX;
const bool isCombining = utf8IsCombiningMark(cp);
int raiseBy = 0;
if (isCombining && hasBaseGlyph) {
const int currentGap = glyph->top - glyph->height - lastBaseTop;
if (currentGap < MIN_COMBINING_GAP_PX) {
raiseBy = MIN_COMBINING_GAP_PX - currentGap;
}
}
const int glyphBaseX = (isCombining && hasBaseGlyph) ? (lastBaseX + lastBaseAdvance / 2) : cursorX;
const int glyphBaseY = cursorY - raiseBy;
*minX = std::min(*minX, glyphBaseX + glyph->left);
*maxX = std::max(*maxX, glyphBaseX + glyph->left + glyph->width);
*minY = std::min(*minY, glyphBaseY + glyph->top - glyph->height);
*maxY = std::max(*maxY, glyphBaseY + glyph->top);
if (!isCombining) {
lastBaseX = cursorX;
lastBaseAdvance = glyph->advanceX;
lastBaseTop = glyph->top;
hasBaseGlyph = true;
cursorX += glyph->advanceX;
}
}
}