bug#43128: Acknowledgement (27.1; DPI change not detected after switching to Emacs 27.1)

[Eli Zaretskii <eliz@gnu.org>]

> Date: Wed, 02 Sep 2020 17:18:40 +0300
> From: Eli Zaretskii <eliz@gnu.org>
> Cc: 43128@debbugs.gnu.org, bernat@luffy.cx
> 
> > Date: Wed, 02 Sep 2020 16:58:59 +0900
> > From: YAMAMOTO Mitsuharu <mituharu@math.s.chiba-u.ac.jp>
> > Cc: 43128@debbugs.gnu.org
> > 
> > > After investigating a bit, I see that `read_settings()' is correctly
> > > called and the DPI retrieved is correct. However, `apply_xft_settings()'
> > > seems to be a noop for me.
> > 
> > The function apply_xft_settings wasn't a no-op when I originally
> > removed the dependency on Xft if USE_CAIRO.  But it was changed to a
> > no-op as a workaround for Bug#36284.
> 
> Bug#36284 seems to be about an issue unrelated to DPI scaling.  is
> there perhaps a way to keep parts of it that will allow to adapt to
> the DPI change?
> 
> > As I mentioned in https://debbugs.gnu.org/cgi/bugreport.cgi?bug=36284#8,
> > a proper fix would be to implement replacements for
> > XftDefaultSubstitute and XftDefaultSet.
> 
> How complicate will such a change be?  Will it be simple and safe
> enough to allow installing such a change on the emacs-27 branch?

Ping!  Could we please try solving this for Emacs 27.2?  Mitsuharu,
could you please show the fix you had in mind back then?

Thanks.