Make double clicking to toggle fullscreen work under Wayland

The 'fullscreen' property is not available when using opengl-cb.
Temporarily work around this by hard coding the binding and use GAction
to toggle fullscreen. A more permanent solution would be to allow
GActions to be activated from an input command.

src/def.h

@@ -54,7 +54,6 @@
 					"UP no-osd seek 60",\
 					"DOWN no-osd seek -60",\
 					"Q quit_watch_later",\
-					"MOUSE_BTN0_DBL cycle fullscreen",\
 					"MOUSE_BTN2 cycle pause",\
 					NULL }
 

src/main.c

@@ -337,6 +337,15 @@ static gboolean mouse_press_handler(	GtkWidget *widget,
 	{
 		mpv_command_string(ctx->mpv_ctx, command);
 	}
+	else if(btn_event->button == 1 && btn_event->type == GDK_2BUTTON_PRESS)
+	{
+		GAction *action;
+
+		action = g_action_map_lookup_action
+				(G_ACTION_MAP(ctx->app), "fullscreen");
+
+		g_action_activate(action, NULL);
+	}
 
 	return TRUE;
 }