Bug#935896: xfce4 fails to resize with SPICE viewer

[Martin <bugs.m1@kkk-web.de>]

Subject: xfce4 fails to resize with SPICE viewer
Package: xfce4
Version 4.12.5
Severity: important

Dear Maintainer,

I upgraded from "jessie" to "stretch" and further on to "buster".
The system is running as a VM on a Linux KVM host (CentOS 7 with [1]) and uses XFCE4 as window manager.
SPICE [2] is installed on the VM.
Connection to the VM via SPICE with remote-viewer.exe [3] from a windows machine.

Screen resolution did change automatically in XFCE on "jessie" when resizing the viewer window.
Now this is broken in "buster" due to a change in spice-vdagent as stated here: [4] Spice-vdagent now just informs the window manager that a resolution change has taken place. XFCE4 ignores this notification and does _not_ resize.

Expectation: XFCE needs to be fixed. Otherwise XFCE4 can not be properly used with SPICE as it does not resize.



[1]
spice-glib-0.35-2.el7.x86_64
spice-gtk3-0.35-2.el7.x86_64
spice-server-0.14.0-6.el7_6.1.x86_64

[2]
ii  libspice-client-gtk-3.0-4    0.25-1+deb8u1
ii  spice-vdagent                0.18.0-1

[3]
https://virt-manager.org/download/
https://virt-manager.org/download/sources/virt-viewer/virt-viewer-x64-8.0.msi

[4]
https://bugzilla.redhat.com/show_bug.cgi?id=1290586#c7
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=858549#15


-- System Information:
Debian Release: 10.0
  APT prefers stable
  APT policy: (500, 'stable')
Architecture: amd64 (x86_64)

Kernel: Linux 4.19.0-5-amd64 (SMP w/1 CPU core)
Locale: Lang=de_DE.UTF-8, LC_CTYPE=de_DE.UTF-8 (charmap=UTF-8) (ignored: LC_ALL set to de_DE.UTF-8), LANGUAGE=de_DE.UTF-8 (charmap=UTF-8) (ignored: LC_ALL set to de_DE.UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)
LSM: AppArmor: enabled

Versions of packages xfce4 depends on:
ii  gtk2-engines-xfce        3.2.0-4
ii  libxfce4ui-utils        4.12.1-3
ii  thunar                    1.8.4-1
ii  xfce4-appfinder            4.12.0-2
ii  xfce4-panel                4.12.2-1
ii  xfce4-pulseaudio-plugin    0.4.1-1
ii  xfce4-session            4.12.1-6
ii  xfce4-settings            4.12.4-1
ii  xfconf                    4.12.1-1
ii  xfdesktop4                4.12.4-2
ii  xfwm4                    4.12.5-1