[Fontconfig] Another proposal for saving custom fonts in fontconfig

[Peng Wu]

Hi,

On Tue, 2019-07-02 at 18:12 +0900, Akira TAGOH wrote:
> No. I thought we agreed with not using blackboxed parameters in
> private discussions. that API potentially expects to override
> everything with FcPattern which isn't desired at this point. if you
> want to override a property other than FC_FONT_VARIATIONS, it should
> be "const FcChar8 *object, const FcChar8 *value" instead of
> "FcPattern *custom".

I think if the user supply some property which is not allowed to
be overridden, fontconfig can print warnings and ignore that property.

And initially I think we need only to implement to set the font
variations and features properties, for other properties just print
warnings and ignore it in fontconfig.

Thanks,
  Peng