bug#25945: Emacs aborts while calling FT_Load_Glyph

[Werner LEMBERG <wl@gnu.org>]

>> New code for (a) is quite simple:
>> 
>>   if (FT_Load_Glyph (ft_face, g->g.code, FT_LOAD_DEFAULT) != 0)
>>     if (FT_Load_Glyph (ft_face, g->g.code, FT_LOAD_NO_HINTING) != 0)
>>       ...
> 
> This should probably be accompanied by a suitable FONT_ADD_LOG call,
> to mention that this fallback was taken.

Yes, perhaps.  However, if all glyphs are broken you will get a huuge
logfile...

>> My knowledge of Emacs internals is too small to provide an
>> implementation for (b).
> 
> I think it's too late for (b) when we discover this problem in
> ftfont_get_metrics.  To do (b) we should have discovered this in
> ftfont_has_char, or thereabouts.

Interesting.  How comes that Emacs aborts right there?

A note regarding the Padauk font: The problem is partly due to
FreeType 2.7.1, which has a stricter looping limit for TrueType
bytecode to detect endless loops – for this font, however, the limit
is a bit too strict; I will fix this in the next FreeType release.
Regardless of that, the bytecode in Padauk *is* buggy, and I've
already contacted the maintainers, asking for a new release using a
new, fixed ttfautohint version.

  https://github.com/silnrsi/font-padauk/issues/12


     Werner