MetaScreen: Add tracking of whether there are fullscreen windows

Trying to track the fullscreen status outside of Mutter, as GNOME Shell
was doing previously, was very prone to errors, because Mutter has a
very tricky definition of when a window is set to be fullscreen and
*actually* acting like a fullscreen window.

 * Add meta_screen_get_monitor_in_fullscreen() and an
   ::in-fullscreen-changed signal. This allows an application to
   track when there are fullscreen windows on a monitor.

 * Do the computation of fullscreen status in a "later" function that
   runs after showing, so we properly take focus into account.

 * To get ordering of different phases right, add more values
   to MetaLaterType.

 * Add auto-minimization, similar to what was added to GNOME Shell
   earlier in this cycle - if a window is set to be fullscreen, but
   not actually fullscreen, minimize.

https://bugzilla.gnome.org/show_bug.cgi?id=649748

src/meta/screen.h

@@ -82,6 +82,9 @@ void meta_screen_get_monitor_geometry (MetaScreen    *screen,
                                        int            monitor,
                                        MetaRectangle *geometry);
 
+gboolean meta_screen_get_monitor_in_fullscreen (MetaScreen  *screen,
+                                                int          monitor);
+
 int meta_screen_get_monitor_index_for_rect (MetaScreen    *screen,
                                             MetaRectangle *rect);
 

src/meta/util.h

@@ -167,12 +167,18 @@ GPid meta_show_dialog (const char *type,
  * MetaLaterType:
  * @META_LATER_RESIZE: call in a resize processing phase that is done
  *   before GTK+ repainting (including window borders) is done.
+ * @META_LATER_CALC_SHOWING: used by Mutter to compute which windows should be mapped
+ * @META_LATER_CHECK_FULLSCREEN: used by Mutter to see if there's a fullscreen window
+ * @META_LATER_SYNC_STACK: used by Mutter to send it's idea of the stacking order to the server
  * @META_LATER_BEFORE_REDRAW: call before the stage is redrawn
  * @META_LATER_IDLE: call at a very low priority (can be blocked
  *    by running animations or redrawing applications)
  **/
 typedef enum {
   META_LATER_RESIZE,
+  META_LATER_CALC_SHOWING,
+  META_LATER_CHECK_FULLSCREEN,
+  META_LATER_SYNC_STACK,
   META_LATER_BEFORE_REDRAW,
   META_LATER_IDLE
 } MetaLaterType;