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LibTTF+LibGfx: Improve vertical alignment of glyphs

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Before this patch, some glyphs had a weird off-by-1 vertical position
which looked really jarring at small font sizes.

This was caused by glyph bitmaps having different heights from each
other. (Each glyph bitmap was minimally sized to fit only the glyph
itself, and then vertically positioned during the paint phase.
Since this vertical positioning was integer based, subpixel precision
was lost and things ended up looking wonky.)

Fix this by making all glyph bitmaps be the same height so we can blit
them at the same integer y position. We use the typographic ascent from
the OS/2 table to transform the glyph coordinates.

The end result is a huge improvement visually. :^)
This commit is contained in:
Andreas Kling 2021-07-20 01:43:39 +02:00
parent e984200206
commit 9f601fcbcf
4 changed files with 12 additions and 12 deletions
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2
Userland/Libraries/LibTTF/Font.cpp
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@ -425,7 +425,7 @@ RefPtr<Gfx::Bitmap> Font::rasterize_glyph(u32 glyph_id, float x_scale, float y_s
}
auto glyph_offset = m_loca.get_glyph_offset(glyph_id);
auto glyph = m_glyf.glyph(glyph_offset);
return glyph.rasterize(x_scale, y_scale, [&](u16 glyph_id) {
return glyph.rasterize(m_os2.typographic_ascender(), m_os2.typographic_descender(), x_scale, y_scale, [&](u16 glyph_id) {
if (glyph_id >= glyph_count()) {
glyph_id = 0;
}