From time to time, RubyMine suddenly did not accept any keyboard input and felt crashed, while mouse interaction was still possible. This apparently happens to all IntelliJ IDEs, especially on Ubuntu 14.04.
I've managed to fix it by having a shell script that exports
XMODIFIERS="" when launching RubyMine, like this:
#!/bin/sh XMODIFIERS= /home/arne/rubymine/bin/rubymine.sh
It has been working reliably for me ever since, at least until RubyMine 8.
An alternate solution suggested on the Jetbrains issue tracker is setting
#!/bin/sh IBUS_ENABLE_SYNC_MODE=1 /home/arne/rubymine/bin/rubymine.sh
This seems fix issues on RubyMine 8.
The benefit of an extra launcher file is that you can upgrade RubyMine and don't have to touch your launcher.
As the solutions above seem to handle a problem with IBus, you can try to disable IBus completely. IBus can be used to switch between keyboard input languages, but Mate still allows to switch languages/layouts in the Keyboard > Layouts settings.
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