Add a test for deriving accessible implementations

This is a trivial example. Just check that we can derive
from GtkButtonAccessible, and have a GtkButton subclass
use the derived accessible implementation.

tests/a11y/Makefile.am

@@ -29,6 +29,8 @@ TEST_PROGS += text
 
 TEST_PROGS += children
 
+TEST_PROGS += derive
+
 # the focus test has no chance of working until
 # all the idle handlers in gail are gone
 #

tests/a11y/derive.c

@@ -0,0 +1,73 @@
+/*
+ * Copyright (C) 2012 Red Hat Inc.
+ *
+ * Author:
+ *      Matthias Clasen <mclasen@redhat.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Library General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Library General Public License for more details.
+ *
+ * You should have received a copy of the GNU Library General Public
+ * License along with this library. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <gtk/gtk.h>
+#include <gtk/gtk-a11y.h>
+
+/* Implement a (trivial) GtkButton subclass, derive GtkButtonAccessible
+ * and use the derived accessible for our new button.
+ */
+
+typedef GtkButtonAccessible MyButtonAccessible;
+typedef GtkButtonAccessibleClass MyButtonAccessibleClass;
+
+G_DEFINE_TYPE (MyButtonAccessible, my_button_accessible, GTK_TYPE_BUTTON_ACCESSIBLE)
+
+static void
+my_button_accessible_init (MyButtonAccessible *a)
+{
+}
+
+static void
+my_button_accessible_class_init (MyButtonAccessibleClass *class)
+{
+}
+
+typedef GtkButton MyButton;
+typedef GtkButtonClass MyButtonClass;
+
+G_DEFINE_TYPE (MyButton, my_button, GTK_TYPE_BUTTON)
+
+static void
+my_button_init (MyButton *b)
+{
+}
+
+static void
+my_button_class_init (MyButtonClass *class)
+{
+  gtk_widget_class_set_accessible_type (GTK_WIDGET_CLASS (class),
+                                        my_button_accessible_get_type ());
+}
+
+int main (int argc, char *argv[])
+{
+  GtkWidget *widget;
+  GtkAccessible *accessible;
+
+  gtk_init (NULL, NULL);
+
+  widget = GTK_WIDGET (g_object_new (my_button_get_type (), NULL));
+  accessible = GTK_ACCESSIBLE (gtk_widget_get_accessible (widget));
+
+  g_assert (G_TYPE_CHECK_INSTANCE_TYPE (accessible, my_button_accessible_get_type ()));
+
+  return 0;
+}