Fix occasional crashes in alt-tab-switch

src/Main.vala

@@ -27,6 +27,8 @@ namespace Gala
 		
 		Window? moving; //place for the window that is being moved over
 		
+		int modal_count; //count of modal modes overlaying each other
+		
 		Gee.HashSet<Meta.WindowActor> minimizing = new Gee.HashSet<Meta.WindowActor> ();
 		Gee.HashSet<Meta.WindowActor> maximizing = new Gee.HashSet<Meta.WindowActor> ();
 		Gee.HashSet<Meta.WindowActor> unmaximizing = new Gee.HashSet<Meta.WindowActor> ();
@@ -162,6 +164,11 @@ namespace Gala
 		
 		public new void begin_modal ()
 		{
+			if (modal_count != 0) {
+				return;
+			}
+			modal_count ++;
+			
 			var screen = get_screen ();
 			var display = screen.get_display ();
 			
@@ -170,6 +177,9 @@ namespace Gala
 		
 		public new void end_modal ()
 		{
+			if (modal_count > 0)
+				modal_count --;
+			if (modal_count == 0)
 				base.end_modal (get_screen ().get_display ().get_current_time ());
 		}
 		

src/Widgets/WindowSwitcher.vala

@@ -28,6 +28,8 @@ namespace Gala
 		
 		Meta.Window? current_window;
 		
+		bool active; //switcher is currently running
+		
 		public WindowSwitcher (Gala.Plugin _plugin)
 		{
 			plugin = _plugin;
@@ -37,7 +39,14 @@ namespace Gala
 		{
 			if (((event.modifier_state & ModifierType.MOD1_MASK) == 0) || 
 					event.keyval == Key.Alt_L) {
+				close (event.time);
+			}
 			
+			return true;
+		}
+		
+		void close (uint time)
+		{
 			foreach (var clone in window_clones) {
 				remove_child (clone);
 				clone.destroy ();
@@ -54,11 +63,12 @@ namespace Gala
 			window_clones.clear ();
 			
 			plugin.end_modal ();
-				current_window.activate (event.time);
+			if (current_window != null) {
+				current_window.activate (time);
 				current_window = null;
 			}
 			
-			return true;
+			active = false;
 		}
 		
 		public override bool captured_event (Clutter.Event event)
@@ -113,6 +123,14 @@ namespace Gala
 		public void handle_switch_windows (Meta.Display display, Meta.Screen screen, Meta.Window? window,
 			X.Event event, Meta.KeyBinding binding)
 		{
+			if (active) {
+				if (window_clones.size != 0)
+					close (screen.get_display ().get_current_time ());
+				return;
+			}
+			
+			active = true;
+			
 			var metawindows = display.get_tab_list (Meta.TabList.NORMAL, screen, screen.get_active_workspace ());
 			if (metawindows.length () <= 1)
 				return;

src/Widgets/WorkspaceView.vala

@@ -100,6 +100,8 @@ namespace Gala
 					screen.remove_workspace (screen.get_workspaces ().nth_data (i), screen.get_display ().get_current_time ());
 				}
 			}
+			
+			add_workspace ();
 		}
 		
 		bool draw_background (Cairo.Context cr)