Crash on QEMU guest with virtio VGA if window is resized

[Leonardo Müller]

When using Xubuntu on QEMU with virtio VGA xfce4-display-settings crash if the QEMU window was resized. If using xrandr to adjust the resolution then xfce4-display-settings starts to work again.

This is the backtrace:

(gdb) bt
#0 convert_xfce_output_info (output_id=<optimized out>) at main.c:1668
#1 0x000055555555c4a3 in get_output_for_window (window=<optimized out>) at main.c:2754
#2 select_current_output_from_dialog_position (app=0x555555b6ba00) at main.c:2791
#3 dialog_map_event_cb (widget=<optimized out>, event=<optimized out>, data=0x555555b6ba00) at main.c:2805
#4 0x00007ffff749d38b in ?? () from /usr/lib/x86_64-linux-gnu/libgtk-x11-2.0.so.0
#5 0x00007ffff66fb10d in g_closure_invoke () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#6 0x00007ffff670dbf1 in ?? () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#7 0x00007ffff67160af in g_signal_emit_valist () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#8 0x00007ffff671712f in g_signal_emit () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#9 0x00007ffff75b32bc in ?? () from /usr/lib/x86_64-linux-gnu/libgtk-x11-2.0.so.0
#10 0x00007ffff749bb03 in gtk_main_do_event () from /usr/lib/x86_64-linux-gnu/libgtk-x11-2.0.so.0
#11 0x00007ffff711102c in ?? () from /usr/lib/x86_64-linux-gnu/libgdk-x11-2.0.so.0
#12 0x00007ffff5931387 in g_main_context_dispatch () from /usr/lib/x86_64-linux-gnu/libglib-2.0.so.0
#13 0x00007ffff59315c0 in ?? () from /usr/lib/x86_64-linux-gnu/libglib-2.0.so.0
#14 0x00007ffff59318d2 in g_main_loop_run () from /usr/lib/x86_64-linux-gnu/libglib-2.0.so.0
#15 0x00007ffff749aa37 in gtk_main () from /usr/lib/x86_64-linux-gnu/libgtk-x11-2.0.so.0
#16 0x00005555555617e1 in display_settings_show_main_dialog (display=<optimized out>) at main.c:2899
#17 0x000055555555b465 in main (argc=<optimized out>, argv=<optimized out>) at main.c:3201

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: xfce4-settings 4.12.4-0ubuntu0.18.04.1
ProcVersionSignature: Ubuntu 4.15.0-43.46-generic 4.15.18
Uname: Linux 4.15.0-43-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.5
Architecture: amd64
CurrentDesktop: XFCE
Date: Sun Dec 30 17:23:54 2018
InstallationDate: Installed on 2018-12-30 (0 days ago)
InstallationMedia: Xubuntu 18.04.2 LTS "Bionic Beaver" - Beta amd64 (20181230)
SourcePackage: xfce4-settings
UpgradeStatus: No upgrade log present (probably fresh install)