[Draft]: Add missing tables to OpenType definition

[archaephyrryx]

Missing Tables in Extant Implementation

Current Slate

• prep
• gasp
• BASE
  • v1.x Fields
  • v1.1 Fields
• GDEF
• GPOS
  • Non-Subtable Aspects
  • v1.1 Fields
  • SinglePos
  • PairPos
  • CursivePos
  • MarkBasePos
  • MarkLigPos
  • MarkMarkPos
  • PosExtension
  • (Common with GSUB) SequenceContext
  • (Common with GSUB) ChainedSequenceContext
• GSUB
  • Non-Subtable Aspects
  • v1.1 Fields
  • SingleSubst
  • MultipleSubst
  • AlternateSubst
  • LigatureSubst
  • SubstExtension
  • ReverseChainSingleSubst
• 'vhea'
• 'vmtx'
• 'kern'
• 'STAT'
• fvar
• gvar

Deliberately Deferred

• CFF
• CFF2
• VORG

Low Priority

• SVG
• EBDT
• EBLC
• EBSC
• CBDT
• CBLC
• sbix
• JSTF
• MATH
• DSIG

Metrics (out of 659 fonts)

    239 CFF20: [MISSING IMPL]
    137 DSIG: [MISSING IMPL]
     87 FFTM: [MISSING IMPL]
     77 hdmx: [MISSING IMPL]
     72 VDMX: [MISSING IMPL]
     66 LTSH: [MISSING IMPL]
     29 PCLT: [MISSING IMPL]
     27 TSIa9: [MISSING IMPL]
     22 STAT: [MISSING IMPL]
     21 fvar: [MISSING IMPL]
     19 TSI0: [MISSING IMPL]
     19 gvar: [MISSING IMPL]
     18 TSI1: [MISSING IMPL]
     17 TTFA: [MISSING IMPL]
     15 SVG20: [MISSING IMPL]
     15 HVAR: [MISSING IMPL]
     15 EBLC: [MISSING IMPL]
     15 EBDT: [MISSING IMPL]
     13 VORG: [MISSING IMPL]
     10 TSI4: [MISSING IMPL]
     10 TSI2: [MISSING IMPL]
      9 TSI5: [MISSING IMPL]
      9 meta: [MISSING IMPL]
      8 MVAR: [MISSING IMPL]
      6 mort: [MISSING IMPL]
      6 CFF2: [MISSING IMPL]
      6 avar: [MISSING IMPL]
      5 Sill: [MISSING IMPL]
      5 Silf: [MISSING IMPL]
      5 Gloc: [MISSING IMPL]
      5 Glat: [MISSING IMPL]
      5 Feat: [MISSING IMPL]
      5 BDF20: [MISSING IMPL]
      4 JSTF: [MISSING IMPL]
      3 TSIV: [MISSING IMPL]
      3 MTfn: [MISSING IMPL]
      3 morx: [MISSING IMPL]
      3 feat: [MISSING IMPL]
      2 MATH: [MISSING IMPL]
      2 CBLC: [MISSING IMPL]
      2 CBDT: [MISSING IMPL]
      1 Zapf: [MISSING IMPL]
      1 TSIS: [MISSING IMPL]
      1 TSIP: [MISSING IMPL]
      1 TSID: [MISSING IMPL]
      1 Silt: [MISSING IMPL]
      1 sbix: [MISSING IMPL]
      1 PfEd: [MISSING IMPL]
      1 MERG: [MISSING IMPL]
      1 fond: [MISSING IMPL]
      1 cvar: [MISSING IMPL]
      1 CPAL: [MISSING IMPL]
      1 COLR: [MISSING IMPL]
      1 bloc: [MISSING IMPL]
      1 bdat: [MISSING IMPL]

[archaephyrryx]

Note: the implementation (or possibly, its interaction with the engine) for gvar is currently very bugged, but it may be a good idea to merge this as-is to avoid too much drift from main being locked behind a monolithic PR.