Comment 4 for bug 736404

I thought about this a little bit.

It happens with Full screen mode, and it also happens with "Grab Input" Option in windowed mode (not mentioned yet).
F key in game or editor toggles full screen and also enables it.
Alt-Tab is completely caught inside the game and not handed outside to the WM.

So I propose the following:

Catch Alt-Tab inside the game, check if we are fullscreen or have grab mode.
If fullscreen - toggle to windowed (just like F key). Then hand out the Alt-Tab event to the WM.
If Windowed and grab mode - disable grabbing, then hand out the Alt-Tab event to the WM.

After regaining Focus, re-enable fullscreen or grab mode.

Of course, this behavior should be only present on Linux (what about Mac?) but surely not on Windows.
I could also imagine an option in the menu.