Your window manager gets the any key events before applications do, so if it wants to consume those events, it does so and your applications will never receive them. If the window manager does not want to react to the key events itself, it passes them along to the application.

You can verify this by yourself in the following way:

1. Start a terminal.


2. Start xev | grep KeyPress, the X event viewer.


3. Press Alt, note that xev shows that it got the key event in its terminal window.


4. Press Ctrl, again note that xev got the event. Take note of what the terminal window looks like right now.


5. Press Left arrow to go to another workspace. (I'm assuming you have that as a window manager shortcut key.)


6. Press Right arrow to go back to where you are running xev. Note that it never received any key events for you switching workspaces via left and right arrow keys -- the output is the same as it was in Step 4.

So you see that the window manager in practice gets all key events and if it does not want to capture them, it passes them along to the application. The application then gets to do the same for its own widgets (like how you can press Enter all day long in your web browser but it won't do anything until you put the cursor in the address bar or some field where you can enter text).

It is up to the application to set its own shortcuts, and applications are configured independently of each other.

In KDE 3.x, if I recall correctly, you could set the default shortcuts (e.g. Ctrl-s for save) in the KDE Control Center and it would apply to all applications written with the Qt toolkit, but I don't know if that's still possible since their switch to KDE 4.