Guix Emacs: use XRandr rather than Gdk?

[Benjamin Slade <beoram@gmail.com>]

In both flown-blown GuixSD as well as Guix on a foreign distro, Guix's
Emacs seems to use "Gdk" rather than "XRandr" to get screen/monitor
information. Every other packaged version of Emacs I've tried uses
"XRandr" to get screen/monitor information. This is an issue because
"Gdk" apparently doesn't know about individual screens/monitors, but
only about the aggregate area, whereas "XRandr" returns individual
screen names (e.g. "DVI-1") and their respective areas. This means that,
on multi-monitor, where Emacs packages use the `frame.el` library, there
is no way of distinguishing screens/monitors (problematically for
packages which try to make reference to different screens,
e.g. https://gitlab.com/emacsomancer/equake ). I thought I'd start here,
since I've only found this behaviour on Guix, and `frame.el` doesn't
seem to be very forthcoming about how it decides whether to use 'Gdk' or 'XRandr'.

 -Ben

-- 
Benjamin Slade - https://babbagefiles.xyz - https://slade.jnanam.net
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