Currently fontconfig's decision on which font to use for a specific
glyph is influenced by the following:
* which charsets the font package has registered in defoma. If the font
has registered itself for ISO8859-1, fontconfig will consider the font
suitable for that codepoint range. Same is true for all other charsets.
minor correction: fontconfig makes its own charset coverage determination - defoma merely symlinks fonts into a place fontconfig can find them. (and builds alias lists, etc based on defoma information)
> - Whether we need DeFoMa
Yes, as legacy X, GTK1 and QT apps depend on it.
Fontconfig also uses the settings to determine the character sets
provided by the fonts.
AFAIK, it is also used to register fonts for ghostscript... however I'm
not an expert on this and it seems to me that it does not always work as
planned.
Yes, defoma still registers fonts with ghostscript. In this day and age though, if you forget to embed your fonts into your postscript doc you're probably already doing something wrong (and the few bug reports I've investigated re defoma/ghostscript font handling have really been bugs in the postscript producer).
(There's a whole bunch of defoma machinery for supporting the fonts in your printer - and also for tracking an X11 equivalent font to use when rendering printable docs on-screen. These are (dubious) reasons to still have the ghostscript defoma script)