[Fontconfig] Detecting whether a font is a fallback

[Lawrence D'Oliveiro]

On Thu, 20 Apr 2023 00:56:08 +0200, Jean Abou Samra wrote:

> I could compare the two FC_FAMILY values,
> but it seems that Fontconfig does some case transformations — and
> possibly other things like replacing dashes?

If you make a note of the exact family name of the font you want, then
surely matching it again should be enough, shouldn’t it?

    def find_face(family_name) :
        font = ft.find_face(family_name)
        if font.family_name != family_name :
            warnings.warn("font “%s” not found, substituting “%s” instead" % (family_name, font.family_name))
        #end if
        return \
            font
    #end find_face

(Taken from
<https://github.com/ldo/harfpy_examples/blob/master/font_features>.)