bug#44204: Emacs --with-xwidgets complains under Ubuntu 20.04

[Paul Eggert <eggert@cs.ucla.edu>]

On 12/8/21 16:32, Po Lu wrote:

> It works here (on both X11 and Xwayland), but I'm using Fedora
> 35.

That's odd, as I observe some of the problem on Fedora 35 x86-64, using 
the default GNOME login. I built current Emacs master (commit 
63f07ea22f3954c2154d831017caf494911cb515) with './configure 
--with-xwidgets --enable-gcc-warnings', then run 'src/emacs -Q', then in 
the *scratch* buffer type:

(make-xwidget 'webkit "title" 500 500 '())

followed by C-j. On stderr I see this string:

Overriding existing handler for signal 10. Set JSC_SIGNAL_FOR_GC if you 
want WebKit to use a different signal

and in the *Messages* buffer I see:

<xwidget-event> is undefined [4 times]

On this platform, the shell command "env | grep '^XDG' | sort" outputs:

XDG_CURRENT_DESKTOP=GNOME
XDG_DATA_DIRS=/home/eggert/.local/share/flatpak/exports/share:/var/lib/flatpak/exports/share:/usr/local/share/:/usr/share/
XDG_MENU_PREFIX=gnome-
XDG_RUNTIME_DIR=/run/user/1000
XDG_SESSION_CLASS=user
XDG_SESSION_DESKTOP=gnome
XDG_SESSION_TYPE=wayland


> Paul, could you tell me what version of WebKitGTK you are using?

On Fedora 35, 'dnf info' reports:

Name         : webkit2gtk3
Version      : 2.34.1
Release      : 2.fc35


On my Ubuntu 20.04.3 LTS x86-64 platform, where I observe both the above 
issues and the Gdk-WARNINGs I mentioned previously, 'dpkg -s 
libwebkit2gtk-4.0-37' reports:

Version: 2.34.1-0ubuntu0.20.04.1

and "env | grep '^XDG' | sort" outputs:

XDG_CONFIG_DIRS=/etc/xdg/xdg-ubuntu:/etc/xdg
XDG_CURRENT_DESKTOP=ubuntu:GNOME
XDG_DATA_DIRS=/usr/share/ubuntu:/usr/local/share/:/usr/share/:/var/lib/snapd/desktop
XDG_MENU_PREFIX=gnome-
XDG_RUNTIME_DIR=/run/user/1000
XDG_SESSION_CLASS=user
XDG_SESSION_DESKTOP=ubuntu
XDG_SESSION_TYPE=x11