Re: [ft-devel] problems with synthetic cmaps

[Alexei Podtelezhnikov]

On Wed, Aug 16, 2017 at 10:11 AM, Werner LEMBERG <address@hidden> wrote:
>
> 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 :-)
>

Freetype did not use to select any cmap for the font. They might have
used the "last" one, which now becomes Unicode. They do not say how
how it is supposed to work in their opinion. It is rather fragile to
select the last cmap, whatever it is.