window: Handle being headless better

This avoids updating state (such as position, size etc) when going
headless. Eventually, when non-headless, things will be updated again,
and not until then will we be able to update to a valid state.

https://bugzilla.gnome.org/show_bug.cgi?id=730551

src/core/window.c

@@ -3584,6 +3584,8 @@ meta_window_update_for_monitors_changed (MetaWindow *window)
   if (!new)
     new = meta_monitor_manager_get_primary_logical_monitor (monitor_manager);
 
+  if (new && old)
+    {
       if (window->tile_mode != META_TILE_NONE)
         window->tile_monitor_number = new->number;
 
@@ -3597,6 +3599,11 @@ meta_window_update_for_monitors_changed (MetaWindow *window)
       meta_window_move_between_rects (window,
                                       &old->rect,
                                       &new->rect);
+    }
+  else
+    {
+      meta_window_update_monitor (window, FALSE);
+    }
 }
 
 void
@@ -3659,7 +3666,6 @@ meta_window_move_resize_internal (MetaWindow          *window,
    */
 
   gboolean did_placement;
-  guint old_output_winsys_id;
   MetaRectangle unconstrained_rect;
   MetaRectangle constrained_rect;
   MetaMoveResizeResultFlags result = 0;
@@ -3713,7 +3719,8 @@ meta_window_move_resize_internal (MetaWindow          *window,
     g_assert_not_reached ();
 
   constrained_rect = unconstrained_rect;
-  if (flags & (META_MOVE_RESIZE_MOVE_ACTION | META_MOVE_RESIZE_RESIZE_ACTION))
+  if (flags & (META_MOVE_RESIZE_MOVE_ACTION | META_MOVE_RESIZE_RESIZE_ACTION) &&
+      window->monitor)
     {
       MetaRectangle old_rect;
       meta_window_get_frame_rect (window, &old_rect);
@@ -3763,6 +3770,10 @@ meta_window_move_resize_internal (MetaWindow          *window,
                                             did_placement);
     }
 
+  if (window->monitor)
+    {
+      guint old_output_winsys_id;
+
       old_output_winsys_id = window->monitor->winsys_id;
 
       meta_window_update_monitor (window, flags & META_MOVE_RESIZE_USER_ACTION);
@@ -3770,6 +3781,11 @@ meta_window_move_resize_internal (MetaWindow          *window,
       if (old_output_winsys_id != window->monitor->winsys_id &&
           flags & META_MOVE_RESIZE_MOVE_ACTION && flags & META_MOVE_RESIZE_USER_ACTION)
         window->preferred_output_winsys_id = window->monitor->winsys_id;
+    }
+  else
+    {
+      meta_window_update_monitor (window, flags & META_MOVE_RESIZE_USER_ACTION);
+    }
 
   if ((result & META_MOVE_RESIZE_RESULT_FRAME_SHAPE_CHANGED) && window->frame_bounds)
     {
@@ -5352,7 +5368,7 @@ meta_window_recalc_features (MetaWindow *window)
       window->has_maximize_func = FALSE;
     }
 
-  if (window->has_maximize_func)
+  if (window->has_maximize_func && window->monitor)
     {
       MetaRectangle work_area, client_rect;
 

src/wayland/meta-window-wayland.c

@@ -386,12 +386,16 @@ meta_window_wayland_update_main_monitor (MetaWindow *window,
   if (from == to)
     return;
 
+  if (from == NULL || to == NULL)
+    {
+      window->monitor = to;
+      return;
+    }
+
   from_scale = meta_logical_monitor_get_scale (from);
   to_scale = meta_logical_monitor_get_scale (to);
 
-  /* If we are setting the first output, unsetting the output, or the new has
+  if (from_scale == to_scale)
-   * the same scale as the old no need to do any further checking. */
-  if (from == NULL || to == NULL || from_scale == to_scale)
     {
       window->monitor = to;
       return;