[gtk] widget: Queue an allocate on native widgets when changing opacity

[Timm Bäder <baedert src gnome org>]

commit 1339c425a8c9bbb33db45dac7c2d5c95c9f9c867
Author: Timm Bäder <mail baedert org>
Date:   Wed Aug 28 14:24:50 2019 +0200

    widget: Queue an allocate on native widgets when changing opacity
    
    This way the opacity change works on toplevel windows on wayland.

 gtk/gtkwidget.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)
---
diff --git a/gtk/gtkwidget.c b/gtk/gtkwidget.c
index 9dcfd581d5..9d33ffdb66 100644
--- a/gtk/gtkwidget.c
+++ b/gtk/gtkwidget.c
@@ -11287,9 +11287,14 @@ gtk_widget_update_alpha (GtkWidget *widget)
   if (_gtk_widget_get_realized (widget))
     {
       if (GTK_IS_NATIVE (widget))
-       gdk_surface_set_opacity (priv->surface, priv->alpha / 255.0);
-
-      gtk_widget_queue_draw (widget);
+        {
+          gdk_surface_set_opacity (priv->surface, priv->alpha / 255.0);
+          gtk_widget_queue_allocate (widget);
+        }
+      else
+        {
+          gtk_widget_queue_draw (widget);
+        }
     }
 }