st: Ensure to reset all widget theme nodes

Theme node invalidation stops at unmapped widgets, and widgets
that forget to chain up to the default ::style-changed implementation.
This may leave stale nodes that were invalidated on
StThemeContext::changed, but are still set on widgets, and maybe
used for CSS property lookups.

Make sure that theme node invalidation happens always by moving
propagation outside the vfunc, and ensure the theme nodes are reset
across the full actor tree. Emission of ::style-changed, and obtaining
a new theme node may be delayed till when the actor is mapped.

The theme node is also cleared after unparenting an actor to avoid
stale references.

This ensures that all widgets get their theme node cleared after
stylesheet changes, instead of maybe being left with a theme node
that's been cleared of all its properties.

Fixes: https://gitlab.gnome.org/GNOME/gnome-shell/-/issues/2541
https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1223

diff --git a/src/st/st-widget.c b/src/st/st-widget.c
index 7314a6ca5fc26715d47daf672566c7d270fd667d..e48f8264122441e66fc513cc0394121258ee6493 100644 (file)
--- a/src/st/st-widget.c
+++ b/src/st/st-widget.c
@@ -455,17 +455,12 @@ st_widget_parent_set (ClutterActor *widget,
 {
   StWidget *self = ST_WIDGET (widget);
   ClutterActorClass *parent_class;
-  ClutterActor *new_parent;
 
   parent_class = CLUTTER_ACTOR_CLASS (st_widget_parent_class);
   if (parent_class->parent_set)
     parent_class->parent_set (widget, old_parent);
 
-  new_parent = clutter_actor_get_parent (widget);
-
-  /* don't send the style changed signal if we no longer have a parent actor */
-  if (new_parent)
-    st_widget_style_changed (self);
+  st_widget_style_changed (self);
 }
 
 static void
@@ -510,7 +505,6 @@ static void
 st_widget_real_style_changed (StWidget *self)
 {
   clutter_actor_queue_redraw ((ClutterActor *) self);
-  notify_children_of_style_change ((ClutterActor *) self);
 }
 
 void
@@ -530,6 +524,11 @@ st_widget_style_changed (StWidget *widget)
   if (clutter_actor_is_mapped (CLUTTER_ACTOR (widget)))
     st_widget_recompute_style (widget, old_theme_node);
 
+  /* Descend through all children. If the actor is not mapped,
+   * children will clear their theme node without recomputing style.
+   */
+  notify_children_of_style_change (CLUTTER_ACTOR (widget));
+
   if (old_theme_node)
     g_object_unref (old_theme_node);
 }
@@ -1772,8 +1771,6 @@ st_widget_recompute_style (StWidget    *widget,
 
   if (!paint_equal || !geometry_equal)
     g_signal_emit (widget, signals[STYLE_CHANGED], 0);
-  else
-    notify_children_of_style_change ((ClutterActor *) widget);
 
   priv->is_style_dirty = FALSE;
 }
@@ -1795,7 +1792,10 @@ st_widget_ensure_style (StWidget *widget)
   priv = st_widget_get_instance_private (widget);
 
   if (priv->is_style_dirty)
-    st_widget_recompute_style (widget, NULL);
+    {
+      st_widget_recompute_style (widget, NULL);
+      notify_children_of_style_change (CLUTTER_ACTOR (widget));
+    }
 }
 
 /**