fix(glyph): let bake pass options to a technique - #118
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directRasterPlans hard-coded options: undefined for MSDF and Slug, so a technique's own parameters were unreachable from the CLI. Bitmap was the only one whose parameter arrived, and only because --bitmap encodes its strike list positionally. --msdf now takes em-size and pixel-range, parsed and passed to the baker, and a bare --msdf still means the defaults. Slug takes none of its own (SlugBakerOptions is undefined), so it is unchanged. The default em size is 64 atlas texels, and atlas cost is area, so a face set for small copy pays several times over with no way to say so: one multi-script set of 161 code points came to 4.64 MB, where a Telugu face shipped 592 KB for six glyphs. At em-size=32 the same set is 1.33 MB.
thejustinwalsh
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thejustinwalsh
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August 26, 2026 02:36
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glyph bakehard-codesoptions: undefinedfor every technique except Bitmap, so a technique's own bake parameters are unreachable from the CLI. The bakers accept them; the CLI never passes any.Bitmap is the only technique whose parameter arrives, and only because
--bitmap 16,32encodes it positionally.--helpdocuments--msdfas "Embed the default MSDF raster" — the default being the only thing on offer.What this changes
--msdfnow takes optional settings, in the same shape as--bitmap's strike list. A bare--msdfstill means the defaults, so nothing existing changes behaviour.Slug is untouched:
SlugBakerOptionsisundefined, so it genuinely has none of its own.Why it matters
emSizedefaults to 64 atlas texels per em, and atlas cost is area, so a face set for small copy pays several times over with no way to say so. Measured on the same six Telugu glyphs:--msdf(em-size 64)--msdf em-size=32--msdf em-size=24,pixel-range=6Quadrupling the atlas area quadruples the artifact, exactly as expected — and 64 was more than twice what a page setting at 28 css px can show. Across a 20-face multi-script set the difference was 4.64 MB → 1.33 MB.
Note for consumers
Raster options are part of the raster identity. A runtime request naming different options than the artifact was baked with derives a different
rasterKey, finds no matching raster, falls back to runtime generation, and fails withRASTER_SOURCE_UNAVAILABLE. Both sides have to name the same values — worth a line in the docs.Design discussion in #117.