[gtk/wip/synthetic-motion2: 1/4] main: Avoid a crash with crossing event handling

[Matthias Clasen <matthiasc src gnome org>]

commit 864f74ff847370f23b59d8ff17ca9a5522481f87
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.

 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);
 }