[gtk/matthiasc/for-master: 2/2] main: Avoid a crash with crossing event handling

[Matthias Clasen <matthiasc src gnome org>]

commit b6eb85ee72c228fd5f9657dce7ac7d352be57ad3
Author: Matthias Clasen <mclasen redhat com>
Date:   Wed Aug 26 07:26:01 2020 -0400

    main: Avoid a crash with crossing event handling
    
    We are reusing the GtkCrossingData struct for multiple
    calls here, so we need to make sure that the targets
    stay alive from beginning to end.
    
    Fixes: #3090

 gtk/gtkmain.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)
---
diff --git a/gtk/gtkmain.c b/gtk/gtkmain.c
index a517a0e6e7..23c61cd270 100644
--- a/gtk/gtkmain.c
+++ b/gtk/gtkmain.c
@@ -1335,9 +1335,9 @@ gtk_synthesize_crossing_events (GtkRoot         *toplevel,
 
   crossing.type = crossing_type;
   crossing.mode = mode;
-  crossing.old_target = old_target;
+  crossing.old_target = old_target ? g_object_ref (old_target) : NULL;
   crossing.old_descendent = NULL;
-  crossing.new_target = new_target;
+  crossing.new_target = new_target ? g_object_ref (new_target) : NULL;
   crossing.new_descendent = NULL;
   crossing.drop = drop;
 
@@ -1417,6 +1417,9 @@ gtk_synthesize_crossing_events (GtkRoot         *toplevel,
         gtk_widget_set_state_flags (widget, GTK_STATE_FLAG_PRELIGHT, FALSE);
     }
 
+  g_clear_object (&crossing.old_target);
+  g_clear_object (&crossing.new_target);
+
   gtk_widget_stack_clear (&target_array);
 }