[ft-devel] problems with synthetic cmaps

[Werner LEMBERG]

Alexei,


there is a bug report

  https://bugs.chromium.org/p/chromium/issues/detail?id=754574

that directly affects synthesized cmaps.  The corollary: It is a bad
idea to synthesize a Unicode cmap in FreeType if the number of `hits'
is too low.  For symbol fonts like `wingding.ttf' (which intentionally
misses a (3,1) Unicode cmap), almost all glyphs are missing because
the font's glyph names can't be mapped to Unicode.

I see two solutions:

  (1) Don't synthesize a Unicode cmap map for symbol OpenType fonts
     (i.e., fonts having a (3,0) cmap).

  (2) Discard a synthesized Unicode cmap if the number of mappings is
      much lower than the mappings in another cmap of the font.

IMHO solution (2) is the way to go.

Please comment – and implement :-)


    Werner