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be5invis/Breaking the 64K limit.md

Created November 23, 2019 12:33
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Breaking the 64K limit.md

Breaking the 64K limit

  • The next font format (OpenType 2?) should support > 64K glyphs in one font.
  • GID will be 32-bit.
  • A “subset” table would be present to support legacy APIs that expect GID being 16-bit. It is a bijection between 16-bit “Legacy GID” and 32-bit “Real GID”.
  • Legacy API implementations should reject “OT2” fonts if the subset table is absent – which means this font is designed exclusively for new API.
  • A STAT-like mechanism will be used to “break down” an “OT2” font into a family of legacy-API-aware fonts.
  • When processing in legacy software…
    • TTF component references – if still supported – will reference to Real GID rather than Legacy GID.
    • CMAP, GSUB, COLR, SVG entries involving glyphs outside the down-level subset will be ignored.
    • GPOS will not be affected.
@davelab6
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I posted this at OpenType/opentype-layout#14 so it's not lost

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