mate-indicator-applet keyboard menu blank & hangs system

[Matt Mayfield]

This bug is similar, but not identical, to https://bugs.launchpad.net/ubuntu-mate/+bug/1734271

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Here is a 60-second demonstration: https://youtu.be/U71GITpMp08
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Steps to reproduce:
1) Boot latest Ubuntu 18.04 ISO
2) Choose Cupertino layout
3) Open a Terminal
--> Observe that whenever an editable text field has focus, an extra "US" keyboard layout indicator appears
4) Open the Keyboard section of the indicator applet

Expected behavior:
Keyboard menu is shown and system proceeds as normal.

Actual behavior:
Blank white square is shown instead of menu, and entire system becomes unresponsive to keypresses and mouse clicks.

Additional information:
Switch to another terminal with Ctrl-Shift-F1, log in, `killall mate-panel`, switch back to X with Ctrl-Shift-F7. Note that the system is responsive again, minus the mate-panel.

[Matt Mayfield (mdmayfield)]

Some more info:

1) ~/.cache/indicator-applet-complete.log at the time of the system going unresponsive prints many repeated lines of this error message:

_gtk_widget_captured_event: assertion 'WIDGET_REALIZED_FOR_EVENT (widget, event)' failed

This is quite similar to a bug reported in gnome-terminal - https://bugzilla.redhat.com/show_bug.cgi?id=1435911 - with a similar symptom (half-drawn right-click UI element and system unresponsive until the process is killed in a virtual terminal).

2) The crash only happens when the keyboard icon is present. Earlier in the indicator-applet-complete.log, this appears:

Looking at Module: libapplication.so
Connected to Application Indicator Service.
Signal: Entry Added
Request current apps
Building new application entry: org.kde.StatusNotifierItem-3850-1 with icon: input-keyboard at position 0
gtk_distribute_natural_allocation: assertion 'extra_space >= 0' failed

3) ps -ef | grep 3850 (based on the message about org.kde.StatusNotifierItem-3850-1) shows this:

ubuntu-+ 3850 1 0 14:14 ? 00:00:00 /usr/bin/fcitx

4) man fcitx reveals that fcitx is "Free Chinese Input Toy of X - a Chinese IME for XIM"

This may explain why the bug is easiest to reproduce when booting the live image - after installation with only the US English language, I'm not seeing that keyboard icon show up in indicator-appmenu.

[Matt Mayfield (mdmayfield)]

Killing the fcitx process removes the keyboard icon from indicator-appmenu-complete, thus preventing the situation that leads to the system going unresponsive.

That may be a reasonable workaround for those who don't need to use Chinese input or change keyboard layouts, but it doesn't appear to be a full resolution of the issue.

[Martin Wimpress  (flexiondotorg)]

I believe this issue was caused by mate-hud and is now resolved. Can you confirm?

[Matt Mayfield (mdmayfield)]

Thanks for the followup.

In the Beta 1 live ISO, I'm no longer seeing a different, though seemingly related, issue where the Alt key by itself freezes the session.

However I do still see a lockup when opening the Keyboard section of the indicator applet, while booted into the Live CD. Switching to another terminal and `killall fcitx` restores functionality.

In fact, it's not even necessary to change layouts - the bug can be triggered with

1) Boot LiveCD
2) Open Terminal
3) Click the Keyboard icon in the top right

I haven't had this happen after installation; perhaps that's because I don't install any other language support besides English, so fcitx is removed during installation.

[Bojan Markovic (bmarkovic)]

Killing fcitx from a terminal window (Ctrl + Alt + F2) "unfreezes" the session but the desktop is still frozen (no right click), and it stops one from being able to add keyboard layouts etc.

Bottom line, in 18.04 fcitx is still buggy and this bug is still a showstopper.

[Christos (christosmichaelas)]

Using Ubuntu Mate 18.04.1 ISO I’m experiencing the above bug as well. Removing the input applet from the panel let me continue using the live ISO, but isn’t a fix.

[Martin Wimpress  (flexiondotorg)]

This was fixed in ubuntu-mate-meta (1.233) eoan;