At the moment, when you press alt-Tab, you cycle through a list of windows on the current workspace. People use workspaces in many ways, though; some people keep only one application maximised on each workspace. Very many people have asked for the ability to alt-Tab between windows on all workspaces, not just the current one.
There have been many bugs raised about this matter. One approach, taken in GNOME bug 577699 by Alexander Larsson, is to add a new keybinding called switch_windows_all, which can then be re-bound to alt-Tab. This is certainly a possibility, but adds a new keybinding and a new GConf setting. It is apparently how Compiz solves the problem.
A different approach was suggested six years ago by Havoc in GNOME bug 143511. The window list in the panel has the option of toggling between a list of all windows and only the windows on the current workspace. It is contrary to the principle of least astonishment if the windows listed in the alt-Tab display are not the same as those listed in the panel.
Therefore, the window manager should detect this setting in the window panel list and behave accordingly. This could be done simply by reading the setting out of GConf. A more portable way would be to have a new EWMH hint on the root window; however, this was raised on the wm-spec-list in 2007 and was not well received. Generalising GNOME’s panel to all environments may be tricky.
Again, anyone wishing to work on this will have abundant help available; otherwise we will get to it when the bug queue is reduced a little. GNOME bug 143511 is the one to follow.
Photo © Scott Ableman, cc-by-nd.