[Fontconfig] hintslight for CFF fonts

[Werner LEMBERG]

>>>>> Getting some requests to enforce hintslight for CFF fonts. so
>>>>> I'm pondering to add the follow recipe by default and enable it
>>>>> in next release.
>>>>
>>>> What's the justification?
>>>
>>> IIRC the new Adobe CFF hinter hinting levels are out of sync with
>>> the autohinter used with TTF fonts
>
> any more comments on this one?

What a pity that the great improvements of the new CFF hinter stay
unused because of defects in components which can't be controlled by
FreeType.

I suggest the following route.

  . Given that the current version of the Cantarell fonts has broken
    hinting, explicitly disable native CFF hinting for this particular
    font family until it gets fixed by the maintainer (basically, it
    should be simply re-hinted automatically with FontForge – a matter
    of a few minutes' work).

  . 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.

  . It would be great if users could play with FreeType's default
    values of the stem darkening, providing suggestions for better
    values in case the rendering system doesn't use linearized
    blending and too low gamma values, as discussed in the FreeType
    developer's mailing list.  It's straightforward then for
    distributions to apply a localized patch.

This thread should basically answer all questions:

  http://lists.nongnu.org/archive/html/freetype-devel/2013-10/msg00053.html

I really hope that all distribution maintainers read this!


    Werner