[Pkg-libvirt-maintainers] Bug#838929: virt-manager: Does not render remote display unless window is larger than needed

[Matthew Gabeler-Lee]

Package: virt-manager
Version: 1:1.4.0-3
Severity: normal

If the remote VM display window is exactly the size it needs to be, then the
remote display does not render for me.  If I resize the window to be just
one pixel bigger (in either or both dimensions), everything works fine.  Of
course, this totally breaks fullscreen mode if my screen and the remote
screen are the same resolution.

This is happening with both a Windows 10 guest, and a text-mode-only Linux
guest.  In both cases, remote qemu/kvm VMs.

The "doesn't render" extends to not even clearing the window background.  If
the viewer window was partly obscured by another window, and I switch focus
to the viewer and raise it, it leaves whatever pixels were on screen from
the occluding window still there until I resize the window.

Note: this also seems to affect virt-viewer 4.0, but details of that app's
behavior make it harder to see what's going on with this bug.

The requested run with --debug --no-fork doesn't produce any output when
resizing the windows either into or out of the problem state.  It prints
debug messages for connecting to the remote VM and connecting the spice
channels, but once connected, no output on any of the window resizes.

-- System Information:
Debian Release: stretch/sid
  APT prefers testing
  APT policy: (990, 'testing'), (500, 'unstable'), (1, 'experimental')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 4.6.0-1-amd64 (SMP w/8 CPU cores)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)

Versions of packages virt-manager depends on:
ii  dconf-gsettings-backend [gsettings-backend]  0.26.0-2
ii  gconf2                                       3.2.6-3
ii  gir1.2-gtk-3.0                               3.21.5-3
ii  gir1.2-gtk-vnc-2.0                           0.6.0-1
ii  gir1.2-libosinfo-1.0                         0.3.1-5
ii  gir1.2-libvirt-glib-1.0                      0.2.3-2
ii  gir1.2-vte-2.91                              0.45.90-2
ii  librsvg2-common                              2.40.16-1
ii  python-dbus                                  1.2.4-1
ii  python-gi                                    3.22.0-1
ii  python-gi-cairo                              3.22.0-1
ii  python-libvirt                               2.2.0-1
ii  python-requests                              2.11.1-1
pn  python2.7:any                                <none>
pn  python:any                                   <none>
ii  virtinst                                     1:1.4.0-3

Versions of packages virt-manager recommends:
ii  gir1.2-spice-client-gtk-3.0  0.32-1
ii  gnome-icon-theme             3.12.0-2
ii  libvirt-daemon-system        2.2.0-1

Versions of packages virt-manager suggests:
ii  gnome-keyring                         3.20.0-3
ii  python-gnomekeyring                   2.32.0+dfsg-3
pn  python-guestfs                        <none>
ii  ssh-askpass-fullscreen [ssh-askpass]  0.3-3.1
ii  virt-viewer                           4.0-1

-- no debconf information