[cally] Fix a crash on some a11y examples if there isn't accessibility support

Most of the accessibility tests can be executed without the
accessibility support, although it is clear that they will
not work properly (ie using accerciser).

But in some specific cases (right now just the atk event test),
the test will crash if no accessibility support is enabled

Fixes http://bugzilla.clutter-project.org/show_bug.cgi?id=2447

tests/accessibility/cally-atkevents-example.c

@@ -144,7 +144,12 @@ main (int argc, char *argv[])
   if (clutter_init (&argc, &argv) != CLUTTER_INIT_SUCCESS)
     return 1;
 
-  cally_util_a11y_init (&argc, &argv);
+  if (cally_util_a11y_init (&argc, &argv) == FALSE)
+    {
+      g_error ("This example requires the accessibility support, "
+               "especifically AtkUtil implementation loaded, "
+               "as it tries to register and remove event listeners");
+    }
 
   data1.value = 10;
   data2.value = 20;

tests/accessibility/cally-examples-util.c

@@ -115,18 +115,20 @@ _a11y_invoke_module (const gchar  *module_path,
  *
  * Basically it will load the cally module using gmodule functions.
  *
+ * Returns if it was able to init the a11y support or not.
  */
-void
+gboolean
 cally_util_a11y_init (int *argc, char ***argv)
 {
   gchar *bridge_dir = NULL;
   gchar *bridge_path = NULL;
+  gboolean result = FALSE;
 
   if (clutter_get_accessibility_enabled () == FALSE)
     {
       g_warning ("Accessibility: clutter has no accessibility enabled"
                  " skipping the atk-bridge load");
-      return;
+      return FALSE;
     }
 
   bridge_dir = _a11y_check_custom_bridge (argc, argv);
@@ -135,8 +137,10 @@ cally_util_a11y_init (int *argc, char ***argv)
 
   bridge_path = g_module_build_path (bridge_dir, "libatk-bridge");
 
-  _a11y_invoke_module (bridge_path, TRUE);
+  result = _a11y_invoke_module (bridge_path, TRUE);
 
   g_free (bridge_dir);
   g_free (bridge_path);
+
+  return result;
 }

tests/accessibility/cally-examples-util.h

@@ -20,5 +20,5 @@
  * Boston, MA 02111-1307, USA.
  */
 
-void
+gboolean
 cally_util_a11y_init (int *argc, char ***argv);