fix(font): skip the glyphs the shaper marks invisible - #170
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Measure and Draw disagreed about default-ignorable characters. Measure summed every shaped advance; Draw skipped only .notdef. A word joiner therefore reserved a full advance of empty space in the middle of a word, and a soft hyphen — which Go Regular maps to a real hyphen glyph — drew a visible dash mid-word. go-opentype/shape v0.4.0 now zeroes and flags those leftovers (Glyph.Invisible), which fixes the width. This honours the flag when painting: without it a mapped ignorable would still stamp its glyph, now at zero advance, straight on top of the following letter — strictly worse than before. invisible(g) names the rule (.notdef or shaper-hidden) so Draw and any future back-end apply the same one. 100% coverage held; race-clean. Asserted on pixels: six ignorables inside a word leave the measured width and every byte of the surface identical. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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The bug
MeasureandDrawdisagreed about default-ignorable characters.Measuresummed every shaped advance;Drawskipped only.notdef.A word joiner therefore reserved a full advance of empty space in the middle of a word, and a soft hyphen — which Go Regular maps to a real hyphen glyph — drew a visible dash mid-word.
The fix
go-opentype/shape v0.4.0 now zeroes and flags those leftovers (
Glyph.Invisible), which fixes the width. This PR honours the flag when painting.That second half matters: without it a mapped ignorable would still stamp its glyph, now at zero advance, straight on top of the following letter — strictly worse than before the shape fix.
invisible(g)names the rule (.notdefor shaper-hidden) soDrawand any future back-end apply the same one.Verification
go test -race→ 100.0% of statements, race-clean.U+00AD,U+2060,U+200B,U+200D,U+FEFF,U+FE0F) placed inside a word leave the measured width and every byte of the surface identical.🤖 Generated with Claude Code