Add fast-path to GSUB to check coverage
Shaves a good 10% off DejaVu Sans with simple Latin text for me. Now, DejaVu is very ChainContext-intensive, but it's also a very popular font!
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@ -968,6 +968,17 @@ struct SubstLookupSubTable
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inline bool apply (hb_apply_context_t *c, unsigned int lookup_type) const
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{
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TRACE_APPLY ();
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if (likely (lookup_type < Context) ||
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(hb_in_range<unsigned int> (lookup_type, Context, ChainContext) &&
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hb_in_range<unsigned int> (u.header.sub_format, 1, 2)))
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{
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/* Fast path, for most that have coverage in the same place.
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* Note that ReverseChainSingle can also go through this but
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* it's not worth the effort. */
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hb_codepoint_t glyph_id = c->buffer->cur().codepoint;
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unsigned int index = (this+u.header.coverage) (glyph_id);
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if (likely (index == NOT_COVERED)) return TRACE_RETURN (false);
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}
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switch (lookup_type) {
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case Single: return TRACE_RETURN (u.single.apply (c));
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case Multiple: return TRACE_RETURN (u.multiple.apply (c));
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@ -998,7 +1009,10 @@ struct SubstLookupSubTable
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private:
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union {
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USHORT sub_format;
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struct {
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USHORT sub_format;
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OffsetTo<Coverage> coverage;
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} header;
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SingleSubst single;
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MultipleSubst multiple;
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AlternateSubst alternate;
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@ -1009,7 +1023,7 @@ struct SubstLookupSubTable
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ReverseChainSingleSubst reverseChainContextSingle;
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} u;
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public:
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DEFINE_SIZE_UNION (2, sub_format);
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DEFINE_SIZE_UNION (2, header.sub_format);
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};
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