Bug#864344: mate-screensaver: mate screen lock retains alternate ibus input method (cannot login!)

[clayton]

Package: mate-screensaver
Version: 1.16.1-1
Severity: important

I was using ibus to type some Chinese, and stepping away for a few minutes,
locked my screen with alt-ctl-l

When I came back and tried to enter my password to unlock the screen, I
was still typing Chinese via ibus in the password field! And the screen locker ignored the 
keyboard shortcut (typically meta-space, but configurable) to switch back to normal english
keyboard output.

I was finally able to unlock the screen without resorting to pulling the plug,
by selecting "login as a different user", getting the desktop login screen back,
and logging in there as the same user for which the screen was locked.

-- System Information:
Debian Release: 9.0
  APT prefers testing
  APT policy: (990, 'testing'), (700, 'unstable'), (1, 'experimental')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 4.9.0-3-amd64 (SMP w/4 CPU cores)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8), LANGUAGE=en_HK:en (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)

Versions of packages mate-screensaver depends on:
ii  dbus-x11                  1.10.18-1
ii  libatk1.0-0               2.22.0-1
ii  libc6                     2.24-11
ii  libcairo-gobject2         1.14.8-1
ii  libcairo2                 1.14.8-1
ii  libdbus-1-3               1.10.18-1
ii  libdbus-glib-1-2          0.108-2
ii  libgdk-pixbuf2.0-0        2.36.5-2
ii  libgl1-mesa-glx [libgl1]  13.0.6-1+b2
ii  libglib2.0-0              2.50.3-2
ii  libgtk-3-0                3.22.11-1
ii  libice6                   2:1.0.9-2
ii  libmate-desktop-2-17      1.16.2-2
ii  libmate-menu2             1.16.0-2
ii  libmatekbd4               1.16.0-2
ii  libnotify4                0.7.7-2
ii  libpam0g                  1.1.8-3.6
ii  libpango-1.0-0            1.40.5-1
ii  libpangocairo-1.0-0       1.40.5-1
ii  libsm6                    2:1.2.2-1+b3
ii  libstartup-notification0  0.12-4+b2
ii  libsystemd0               232-24
ii  libx11-6                  2:1.6.4-3
ii  libxext6                  2:1.3.3-1+b2
ii  libxklavier16             5.4-2
ii  libxss1                   1:1.2.2-1
ii  libxxf86vm1               1:1.1.4-1+b2
ii  mate-desktop-common       1.16.2-2
ii  mate-screensaver-common   1.16.1-1
ii  mate-session-manager      1.16.1-1

Versions of packages mate-screensaver recommends:
ii  mate-power-manager  1.16.2-1

Versions of packages mate-screensaver suggests:
pn  rss-glx            <none>
ii  xscreensaver-data  5.36-1

-- no debconf information