bug#64310: 29.0.92; pure-GTK warning under Wayland

[Po Lu]

Pankaj Jangid <pankaj@codeisgreat.org> writes:

> Sorry for reporting this so late. I am using pure-GTK build since about
> a year ago and this problem was first observed a few months ago, but I
> am reporting it now because it occurred on my system again today.
>
> I am on a Wayland system (Debian 12 Bookworm). My system is configured
> to use Gnus as default mailto sender. It opens the message window but
> also opens a warning that says, "You are trying to run Emacs configured
> with the "pure-GTK" interface under X Window System". This warning
> doesn't appear when I start Emacs normally. Only occurs when "mailto:";
> is triggered from other application like browser. I am 100% sure that I
> am using Wayland. Because the value of $XDG_SESSION_TYPE is
> "wayland". And "WaylandEnable=false" is commented in my system's
> "/etc/gdm3/daemon.conf".

This dialog cannot be displayed if Emacs is using the GDK Wayland
backend.  Perhaps the WAYLAND_DISPLAY environment variable was not set
when Emacs was started to handle the mailto URI.

How did you configure Emacs to handle such URIs?