When launched via xdg-open emacsclient triggers warning about running pgtk emacs under X

[alexmurray]

Reproduce under wayland desktop on Ubuntu 24.10 using emacs-30 from current beta (30.0.93, rev 2628)

$ emacs -q -e server-start

Then in another terminal

$ XDG_UTILS_DEBUG_LEVEL=10 xdg-open foo.el
 Selected DE gnome3

Spawns a new emacs frame along with the warning dialog saying:

You are trying to run Emacs configured with the "pure-GTK" interface under the X Window System...

And then eventually the original emacs instance will crash.

Can also reproduce by just opening file from Nautilus.

[alexmurray]

We can debug this by invoking the xdg-open shell script with bash -x and we see that it is actually gio open foo.el that gets invoked:

XDG_UTILS_DEBUG_LEVEL=1 bash -x $(which xdg-open) foo.el
+ check_common_commands foo.el
+ '[' 1 -gt 0 ']'
+ parm=foo.el
+ shift
+ case "$parm" in
+ '[' 0 -gt 0 ']'
+ '[' -z 1 ']'
+ '[' 1 -lt 1 ']'
+ xdg_redirect_output=' >&2'
+ '[' xfoo.el '!=' x ']'
+ url=
+ '[' 1 -gt 0 ']'
+ parm=foo.el
+ shift
+ case "$parm" in
+ '[' -n '' ']'
+ url=foo.el
+ '[' 0 -gt 0 ']'
+ '[' -z foo.el ']'
+ detectDE
+ unset GREP_OPTIONS
+ '[' -n ubuntu:GNOME ']'
+ case "${XDG_CURRENT_DESKTOP}" in
+ '[' -z '' ']'
+ '[' -n '' ']'
+ '[' -n this-is-deprecated ']'
+ DE=gnome
+ '[' -z gnome ']'
+ '[' -z gnome ']'
+ '[' xgnome = xgnome ']'
+ command -v gnome-default-applications-properties
+ DE=gnome3
+ '[' -f /run/user/1000/flatpak-info ']'
+ '[' xgnome3 = x ']'
+ DEBUG 2 'Selected DE gnome3'
+ '[' -z 1 ']'
+ '[' 1 -lt 2 ']'
+ return 0
+ case "${BROWSER}" in
+ case "$DE" in
+ open_gnome3 foo.el
+ gio help open
+ gio open foo.el
+ '[' 0 -eq 0 ']'
+ exit_success
+ '[' 0 -gt 0 ']'
+ exit 0

[alexmurray]

$ gio mime $(xdg-mime query filetype foo.el)
Default application for “text/x-emacs-lisp”: emacs_emacsclient.desktop
Registered applications:
	emacs_emacsclient.desktop
	org.gnome.TextEditor.desktop
	vim.desktop
	emacs_emacs.desktop
	libreoffice_writer.desktop
No recommended applications

[alexmurray]

Looking at the man page for gio open it says that it does not set any environment variables when running the application - so it would seem that XDG_SESSION_TYPE which we use in the emacs and emacsclient scripts in the snap will not be set and hence we will default to the X11 based emacs. Instead perhaps we should fallback to the presence of $XDG_RUNTIME_DIR/wayland-0

[alexmurray]

On further investigation, if we make our emacsclient script have set -x at the top we can see the following output when it gets run via xdg-open foo.el:

+ '[' -n wayland ']'
+ '[' wayland = wayland ']'
+ : wayland
+ case "${EMACS_TOOLKIT}" in
+ EMACSCLIENT=emacsclient-wayland
+ '[' -n /var/lib/snapd/desktop/applications/emacs_emacsclient.desktop ']'
+ '[' 121877 -eq 121877 ']'
+ '[' -n /home/amurray/foo.el ']'
+ exec /snap/emacs/x1/usr/bin/emacsclient-wayland --alternate-editor= --display=:0 /home/amurray/foo.el

which indicates we are running the right binary but it is invoked with --display=:0 which is odd - seems xdg-open is passing that along for some reason

[alexmurray]

No... we are setting this ourselves

emacs-snap/emacsclient

Line 41 in 74174fe

exec "$SNAP/usr/bin/$EMACSCLIENT" --alternate-editor= --display="$DISPLAY" "$@"

[alexmurray]

Can confirm this is now fixed in revision 2635 which is built with the associated fix commit above.