[Fontconfig] hintslight for CFF fonts

[Werner LEMBERG]

>> The darkening is not related to the broken Cantarell fonts; these
>> are two completely different issues.
>
> Ah, okay. so it should be consistent regardless of what CFF fonts
> one uses?

Yes.

> [...] I'm sure there are nothing we can do in fontconfig then.
> otherwise we can but it may needs to be turned on and applied per
> fonts.

Exactly.  Until Cantarell gets fixed, users should modify a fontconfig
configuration file so that light hinting is used for this font.

>> 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.
>
> Is it those two "no-stem-darkening" and "darkening-parameters"
> right?

It's the latter: IMHO, some stem darkening should be applied even for
non-linearized blending – there are many professional CFFs that
*expect* darkening by the engine (especially fonts from Adobe, which
is not really suprising).  Otherwise, they are rendered too light and
thin.

In the FreeType discussion thread I was giving a link, modified
`darkening-parameters' values have been suggested.  It would be great
if others could test them too.


    Werner