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In Emacs run in terminal, ctrl+space is a standard shortcut key to select region. But under Ubuntu 12.04, it will invoke some input method for non-English language. I was wondering if I can reserve it for Emacs only?

Under System Settings -> Keyboard -> Shortcuts, I couldn't find to what ctrl+space has been bound. Strange.

Other programs, especially auto-complete in Eclipse, also seem to have a problem handling ctrl+space.

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5 Answers 5

It sounds like you have Ibus running, which uses Ctrl + Space by default to enable/disable the input editor.

You can change the shortcut key assigned to it in Ibus Preferences.

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If Ibus is running in the menubar, you can right-click to choose Preference from the menu. If Ibus is not running in the menubar, you can start the Preferences dialog from the Dash by running Keyboard Input Methods or from the terminal with ibus-setup.

Update for 14.04

ibus-setup is no longer available for 14.04. Functions from the former ibus-setup are instead integrated into System Settings >> Text Entry.

Input switching is now set by default to Super + Space, but Ibus may still steal focus from the Control + Space keybinding and cause other system problems, most notably the auto-complete in Eclipse.

Integration of Ibus input switching into the new Text Entry settings is still a work in progress, and this is causing the problem since the older setting still exists behind the scenes.

If you have upgraded from 12.04, ibus-settings should still be available.

In 14.04, you can edit the settings directly is dconf-editor.

If it is not installed:

sudo apt install dconf-editor

Then browse to Desktop >> ibus >> hotkey. The trigger and triggers setting will still show 'control+space'. Edit these settings out, being careful to leave empty brackets [] in triggers.

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This also fixed autocomplete not working in Eclipse after I upgraded to xubuntu 14.04 –  Brian Laframboise May 6 '14 at 13:50
My ibus-setup on 14.04 is slightly different and does not have that option. –  BoppreH May 6 '14 at 17:50
@BoppreH 14.04 has changed ibus setup a little. I'll look into it. Thanks. –  chaskes May 6 '14 at 17:51
dconf-editor fixed my problem, thank you very much @chaskes . –  BoppreH May 6 '14 at 19:03
@BoppreH Glad it worked out. Please upvote (if you haven't done so). ;) –  chaskes May 6 '14 at 19:04

After upgrade to ubuntu 14.04, I had the same problem. What I did.
In Ibus preferences: System > Preferences > Keyboard Input Methods.
There is an option: Next input method it was set to ctrl+space, I removed that and then all started to work back again.

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Disable the IBUS trigger using the commandline:

gsettings set org.freedesktop.ibus.general.hotkey triggers @as []
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I have Ubuntu 14.04 GNOME with LXDE. Apparently this desktop has ibus-setup. So, for me, changing the ibus setting was the right fix. Perhaps it was only Unity that did away with the ibus-setup app.

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Yes, it's a Unity thing. –  Gunnar Hjalmarsson Dec 28 '14 at 5:02

ibus causes me nothing but headaches. Everytime that I try to change the settings, when I reboot, the Ctrl+Space comes back. Here's my solution:

sudo apt-get purge ibus
sudo killall ibus

Now everything works until Ubuntu decides their next stupid thing. Maybe the letter 'o' will map to turning off the computer?

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