Is there any way to unmap Ctrl+Space from whatever it does by default? It doesn't seem to be listed System Settings->Shortcuts and Gestures.

What Ctrl+Space is supposed to do isn't at all obvious to me, but it's definitely interfering with my use of emacs set-mark-command.

Fedora 16
KDE 4.7.4

Thanks

I don't think that it is mapped to anything by default. That is, it shouldn't be on vanilla kde.

You can try a bit dirty trick - go to global shortcuts and try to set the C-Space shortcut for anything. If it is already registered by a kde application, you'll get the message saying what it currently does.

If you tell it to reassign, press apply, and then clear the shortcut you've just created, it should clear C-Space shortcut.

Some input methods, like iBus and Scim, register Control+Space by default.

Some editors/word-processors use Ctl-Space to insert a non-breaking space. This is such a long-standing convention, I suspect most people would not want to overwrite it with an alternative function.

In Kubuntu 14.04 appeared "IBus -- an intelligent input bus for Linux/Unix" which displays as an applet in the system tray. The default shortcut for "Next input method" is CTRL+SPACE. Unfortunately setting the shortcut is not integrated into KDE shortcuts.