2002-06-26  Mark McLoughlin  <mark@skynet.ie>

        Fixes not being able to tab out of a
        workspace which contains no windows.

        * src/core.c: (meta_core_begin_grab_op): upd
        for meta_display_begin_grab_op change.
        (meta_core_get_grab_frame): allow for
        grab_window == NULL.

        * src/display.[ch]:
        (meta_display_screen_for_xwindow): implement.
        (meta_display_begin_grab_op): grab on the root window
        if window == NULL.
        (meta_display_end_grab_op): use grab_screen instead of
        grab_window.

        * src/keybindings.c:
        (grab_all_keys_and_keyboard): split out from
        meta_window_grab_all_keys.
        (ungrab_all_keys_and_keyboard): split out from
        meta_window_ungrab_all_keys.
        (meta_screen_grab_all_keys), (meta_screen_ungrab_all_keys):
        implement grabbing and ungrabbing on the root window.
        (meta_display_process_key_event): if window == NULL,
        check the event is from the same screen and process. Only
        happens with workspace switching.
        (process_workspace_switch_grab): kill window param and
        don't use grab_window.
        (handle_tab_forward), (handle_begin_move): upd for
        meta_display_begin_grab_op change.
        (handle_workspace_switch): remove brokeness. Always do
        the grab op on the root window.

        * src/keybindings.h: add meta_screen_{un}grab_all_keys.

        * src/window.c: (meta_window_client_message), (menu_callback):
        update for meta_display_begin_grab_op change.