[gimp/gimp-2-6] Bug 627328 - GIMP 2.6.10 segfaults when CTRL-left click on a layer mask

[Michael Natterer <mitch src gnome org>]

commit b23d1635cd435790bffcf50bbff5753d34c9ff97
Author: Christian Krippendorf <Kontakt-Programming CerebrosuS de>
Date:   Sun Oct 10 22:31:35 2010 +0200

    Bug 627328 - GIMP 2.6.10 segfaults when CTRL-left click on a layer mask
    
    Move the g_signal_emit() to the end, because the cell->renderer could
    be changed and cause a segfault. Also check cell->renderer before
    dereferencing it.
    (cherry picked from commit ff03681bdfa371891ec7cc754bfed811c5c434e6)

 app/widgets/gimpcellrendererviewable.c |   41 ++++++++++++++++++--------------
 1 files changed, 23 insertions(+), 18 deletions(-)
---
diff --git a/app/widgets/gimpcellrendererviewable.c b/app/widgets/gimpcellrendererviewable.c
index 3b99696..af3d59b 100644
--- a/app/widgets/gimpcellrendererviewable.c
+++ b/app/widgets/gimpcellrendererviewable.c
@@ -317,31 +317,36 @@ gimp_cell_renderer_viewable_clicked (GimpCellRendererViewable *cell,
                                      const gchar              *path,
                                      GdkModifierType           state)
 {
-  GdkEvent *event;
 
   g_return_if_fail (GIMP_IS_CELL_RENDERER_VIEWABLE (cell));
   g_return_if_fail (path != NULL);
 
-  g_signal_emit (cell, viewable_cell_signals[CLICKED], 0, path, state);
-
-  event = gtk_get_current_event ();
-
-  if (event)
+  if (cell->renderer)
     {
-      GdkEventButton *bevent = (GdkEventButton *) event;
+      GdkEvent *event = gtk_get_current_event ();
 
-      if (bevent->type == GDK_BUTTON_PRESS &&
-          (bevent->button == 1 || bevent->button == 2))
+      if (event)
         {
-          gimp_view_popup_show (gtk_get_event_widget (event),
-                                bevent,
-                                cell->renderer->context,
-                                cell->renderer->viewable,
-                                cell->renderer->width,
-                                cell->renderer->height,
-                                cell->renderer->dot_for_dot);
+          GdkEventButton *bevent = (GdkEventButton *) event;
+
+          if (bevent->type == GDK_BUTTON_PRESS &&
+              (bevent->button == 1 || bevent->button == 2))
+            {
+              gimp_view_popup_show (gtk_get_event_widget (event),
+                                    bevent,
+                                    cell->renderer->context,
+                                    cell->renderer->viewable,
+                                    cell->renderer->width,
+                                    cell->renderer->height,
+                                    cell->renderer->dot_for_dot);
+            }
+
+          gdk_event_free (event);
         }
-
-      gdk_event_free (event);
     }
+
+  /*  emit the signal last so no callback effects can set
+   *  cell->renderer to NULL.
+   */
+  g_signal_emit (cell, viewable_cell_signals[CLICKED], 0, path, state);
 }