[gtk] widget: Always set out value

[Benjamin Otte <otte src gnome org>]

commit 514c3679dc7647db1e64734dab3afc9c9e761e72
Author: Benjamin Otte <otte redhat com>
Date:   Wed Feb 20 04:07:34 2019 +0100

    widget: Always set out value
    
    Don't leave memory in an unitinialized case when returning FALSE from
    gtk_widget_compute_transform().
    
    We both know that people are going to call that function without
    checking the return value.

 gtk/gtkwidget.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)
---
diff --git a/gtk/gtkwidget.c b/gtk/gtkwidget.c
index c3395494ad..21a1ff3333 100644
--- a/gtk/gtkwidget.c
+++ b/gtk/gtkwidget.c
@@ -11245,7 +11245,8 @@ gtk_widget_pick (GtkWidget *widget,
  *
  * Returns: %TRUE if the transform could be computed, %FALSE otherwise.
  *   The transform can not be computed in certain cases, for example when
- *   @widget and @target do not share a common ancestor.
+ *   @widget and @target do not share a common ancestor. In that
+ *   case @out_transform gets set to the identity matrix.
  */
 gboolean
 gtk_widget_compute_transform (GtkWidget         *widget,
@@ -11268,7 +11269,10 @@ gtk_widget_compute_transform (GtkWidget         *widget,
 
   ancestor = gtk_widget_common_ancestor (widget, target);
   if (ancestor == NULL)
-    return FALSE;
+    {
+      graphene_matrix_init_identity (out_transform);
+      return FALSE;
+    }
 
   graphene_matrix_init_identity (&transform);
   for (iter = widget; iter != ancestor; iter = iter->priv->parent)
@@ -11293,7 +11297,10 @@ gtk_widget_compute_transform (GtkWidget         *widget,
       graphene_matrix_multiply (&inverse, &priv->transform, &inverse);
     }
   if (!graphene_matrix_inverse (&inverse, &inverse))
-    return FALSE;
+    {
+      graphene_matrix_init_identity (out_transform);
+      return FALSE;
+    }
 
   graphene_matrix_multiply (&transform, &inverse, out_transform);