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

[Eli Zaretskii]

> 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?

Thanks.