Live previews for hidden windows.

ClutterActors for hidden windows (such windows on different than active
workspaces and windows that are minimized) are available, and reflect the
actual state of the window. This is intended for use in task-switchers etc.

This feature is disabled by default (due to increased demand on resources),
and can be enabled through the metacity/general/live_hidden_windows gconf key.

A trivial sample window switcher is included in the scratch plugin (activated
by clicking on the slide out panel).

src/include/prefs.h

@@ -62,8 +62,9 @@ typedef enum
   META_PREF_COMPOSITING_MANAGER,
 #ifdef WITH_CLUTTER
   META_PREF_CLUTTER_DISABLED,
-  META_PREF_CLUTTER_PLUGINS
+  META_PREF_CLUTTER_PLUGINS,
 #endif
+  META_PREF_LIVE_HIDDEN_WINDOWS,
 } MetaPreference;
 
 typedef void (* MetaPrefsChangedFunc) (MetaPreference pref,
@@ -139,6 +140,10 @@ GSList * meta_prefs_get_clutter_plugins (void);
 void meta_prefs_set_clutter_plugins (GSList *list);
 #endif
 
+gboolean meta_prefs_get_live_hidden_windows (void);
+void     meta_prefs_set_live_hidden_windows (gboolean whether);
+
+
 /* XXX FIXME This should be x-macroed, but isn't yet because it would be
  * difficult (or perhaps impossible) to add the suffixes using the current
  * system.  It needs some more thought, perhaps after the current system