[Fontconfig] hintslight for CFF fonts

[Werner LEMBERG]

>> . FontConfig should implement an interface to FreeType's CFF driver
>>   properties `no-stem-darkening' and `darkening-parameters'.  Those
>>   two are global options (controlling FT_Library, so to say), not
>>   options local to fonts.  In case there are problems I'm open to
>>   suggestions how to improve that on the FreeType side.
>
> I'm a bit concerned about the global option.  I'm not quite sure how
> many CFF fonts are broken at this point and how long font authors
> will take a time to fix.

The darkening is not related to the broken Cantarell fonts; these are
two completely different issues.

As mentioned already, it's not FreeType's fault that current graphics
systems don't do correct blending.  Similarly, it is is not FreeType's
fault that the default gamma value is not correct in most GNU/Linux
distributions.  While the former is a technical problem, the latter
has historical origins, I presume.

> in worst case those global options gives bad effects to fonts
> well-maintained and the maintainer take a quick action for, to work
> around for bad fonts, which isn't well-maintained, outdated and so
> on.

Don't worry about bad fonts!  That's not the problem.  What is
urgently needed is a compensation for the lack of linearized blending
in most graphics stacks.

> plus, there are no syntax so far to let applications know the kind
> of global things in fontconfig.

OK, so controlling the FreeType engine itself doesn't belong to
fontconfig.  What place should be used instead?


    Werner