Cache all fields from PairPos2 and avoid reading subtable#260
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@valadaptive this avoids subtable reparsing entirely for pairpos2. Would you mind checking if this improves your profile? |
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Yes! This speeds up shaping Ubuntu Light by ~8% in the benchmark. |
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Looks good in general. Should we remove the unused impl then? Any way to make this more harmonious across lookup types would be nice. Would it be too heavy to do this kind of caching on every lookups? |
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Yes to all. This needs a bit of cleanup before merging, the code should be better structured to accommodate it and we should try to do this for all lookups. |
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Jan 5, 2026
This extracts the primary coverage table (along with any suitable caches) into a field on `SubtableInfo` so that we can check coverage before attempting to parse the subtable. The glyph id, coverage index, coverage metadata and external cache are then passed to the subtable apply function in a new `ApplyState` parameter. This avoids some buffer indexing and reparsing the primary coverage table. This attempts to clean up and unify some of the caching code paths along with laying some groundwork for future optimizations (like #260). HR benchmarks seem to show a reasonable gain on non-Latin shaping as a bonus.
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Do we still need this? Is it already done? Would the faster read-fonts obviate this? |
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I think this one might still be useful but we’ll need to rebase and measure. |
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Attempt at #256