LibGfx+LibWeb: Follow fontconfig hinting when rasterizing glyphs - #10579
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awesomekling merged 1 commit intoJul 10, 2026
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Glyph positions and advances are produced by HarfBuzz from un-hinted font metrics, but glyphs were rasterized with Skia's default normal hinting. For fonts without a TrueType hinting program, this makes FreeType's autohinter grid-fit glyph outlines horizontally, so the rasterized glyphs no longer line up with the un-hinted advances. The result is visibly uneven spacing, most noticeably a spurious gap before narrow glyphs such as "t". Resolve the hinting configuration from fontconfig per font family and size, honoring family and size-specific configuration rules such as the common rules that disable hinting for DejaVu fonts at small sizes. The query runs the configuration's substitution edits over a pattern describing the font, standing in for a matched font. Results are cached per font. The configuration itself is loaded before the renderer sandbox is installed, and the queries perform no filesystem access, so resolution at rasterization time is sandbox-safe. Test mode pins the hinting style to normal, matching Skia's previous default, so that rendering is deterministic across machines rather than depending on the host's fontconfig configuration.
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Glyph positions and advances are produced by HarfBuzz from un-hinted font metrics, but glyphs were rasterized with Skia's default normal hinting. For fonts without a TrueType hinting program, this makes FreeType's autohinter grid-fit glyph outlines horizontally, so the rasterized glyphs no longer line up with the un-hinted advances. The result is visibly uneven spacing, most noticeably a spurious gap before narrow glyphs such as "t".
Resolve the hinting configuration from fontconfig per font family and size, honoring family and size-specific configuration rules such as the common rules that disable hinting for DejaVu fonts at small sizes. The query runs the configuration's substitution edits over a pattern describing the font, standing in for a matched font. Results are cached per font. The configuration itself is loaded before the renderer sandbox is installed, and the queries perform no filesystem
access, so resolution at rasterization time is sandbox-safe.
Test mode pins the hinting style to normal, matching Skia's previous default, so that rendering is deterministic across machines rather than depending on the host's fontconfig configuration.
Tested by visually comparing this test page:
Before:
After:
Fixes #10344
NB: This will conflict with #10547, which removes the direct fontconfig dependency and goes through Skia. Unfortunately, skia doesn't have the necessary APIs for this, so the direct fontconfig dependency would need to be kept 😞