bug#54564: 29.0.50; [PATCH] Use gsettings font rendering entries for pgtk builds

[Po Lu via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

Eli Zaretskii <eliz@gnu.org> writes:

> Maybe I could help if I understood the difficulty well enough.  What
> exactly is the problem here?  In particular, what is meant by "force a
> re-creation of the font with the changed parameters"?  How can Emacs
> "re-create" a font?

Basically, Emacs needs to close every open font object created by the
ftcr (or ftcrhb) font driver, and open it again, if that makes any
sense.

> AFAIU, this uses gsettings to determine some Emacs font-related
> functionality.  One aspect that bothers me is whether users will have
> the means to tell Emacs to ignore those gsettings and use the usual
> Emacs defaults instead?  I don't think it's a good idea to apply those
> gsettings unconditionally without letting users override that.

I think all the gsettings-related behavior is controlled by
`font-use-system-font', but if it's not, we could always make it work
that way, or add a new variable.

Thanks.