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cmap format 4 glyph lookup

Resolve BMP code points through a font’s format-4 cmap subtable.

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Your result

Example result

How it works

Find the segment covering each code point. Apply idDelta modulo 65536; for a nonzero idRangeOffset, read the relative glyph-array entry and preserve a zero missing-glyph value.

The sample maps U+0041 and U+0042 to glyphs 1 and 2. U+0043 and the sentinel map to missing glyph 0.

Limits

One complete format-4 subtable, not a whole font. Up to 8192 nonoverlapping segments and 10000 queries. No shaping, font rendering, supplementary-plane lookup or glyph-count validation. Structural offsets are checked; full OpenType conformance is not.