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The key binding for isearch-forward-regexp is C-M-s, however I cannot invoke that bindings somehow using Ctrl+Alt+s. I can do Esc then C-s to invoke it though.

Other commands with the C-M prefix works fine using Ctrl+Alt though, like C-M-w (append-next-kill), C-M-f (forward-sexp) etc

Can anybody an idea on what the problem on my system is? I am using GNU Emacs 23.3.1 on Ubuntu 11.10.

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What does Emacs tell you is bound to when you type: C-h k C-M-s? – Trey Jackson Dec 5 '11 at 20:54
It doesn't respond, I still have the "Describe key:" prompt in the minibuffer after pressing Ctrl+Alt+s. I can see what Ctrl+Alt+w is bound to though. – loudandclear Dec 6 '11 at 6:40
That leads me to believe that the window system is not passing that event to Emacs. I'd ask the same question on – Trey Jackson Dec 6 '11 at 16:23
Did you ever figure this out? I'm having the same problem, and google is failing me... – krupan Apr 6 '12 at 23:10
As Trey Jackson indicated, C-M-s was a keyboard shortcut for my operating system and everything worked well after disabling it. – loudandclear Apr 8 '12 at 18:27
up vote 3 down vote accepted

On Ubuntu 11.10, and on Ubuntu 12.04, the "toggle shaded state" keyboard shortcut is assigned to Ctrl+Alt+S by default. Changing it to something else enables the usage of that keybinding inside Emacs.

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Where can I change the binding? – User Jan 29 '13 at 22:55
nvm in 12.10 found it under Settings->Keyboard->Shortcuts – User Jan 29 '13 at 22:56

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