Add a test for the system rgba visual

The main point of this test is to ensure that the pixel_details
getters work as expected.

testsuite/gdk/Makefile.am

@@ -23,6 +23,7 @@ TEST_PROGS += 				\
 	encoding			\
 	keysyms				\
 	rgba				\
+	visual				\
 	$(NULL)
 
 CLEANFILES = 			\

testsuite/gdk/visual.c

@@ -0,0 +1,65 @@
+#include <gdk/gdk.h>
+
+/* We don't technically guarantee that the visual returned by
+ * gdk_screen_get_rgba_visual is ARGB8888. But if it isn't, lots
+ * of code will break, so test this here anyway.
+ * The main point of this test is to ensure that the pixel_details
+ * functions return meaningful values for TrueColor visuals.
+ */
+static void
+test_rgba_visual (void)
+{
+  GdkScreen *screen;
+  GdkVisual *visual;
+  guint32 r_mask, g_mask, b_mask;
+  gint r_shift, g_shift, b_shift;
+  gint r_precision, g_precision, b_precision;
+  gint depth;
+  GdkVisualType type;
+
+  g_test_bug ("764210");
+
+  screen = gdk_screen_get_default ();
+  visual = gdk_screen_get_rgba_visual (screen);
+
+  if (visual == NULL)
+    {
+      g_test_skip ("no rgba visual");
+      return;
+    }
+
+  depth = gdk_visual_get_depth (visual);
+  type = gdk_visual_get_visual_type (visual);
+  gdk_visual_get_red_pixel_details (visual, &r_mask, &r_shift, &r_precision);
+  gdk_visual_get_green_pixel_details (visual, &g_mask, &g_shift, &g_precision);
+  gdk_visual_get_blue_pixel_details (visual, &b_mask, &b_shift, &b_precision);
+
+  g_assert_cmpint (depth, ==, 32);
+  g_assert_cmpint (type, ==, GDK_VISUAL_TRUE_COLOR);
+
+  g_assert_cmphex (r_mask, ==, 0x00ff0000);
+  g_assert_cmphex (g_mask, ==, 0x0000ff00);
+  g_assert_cmphex (b_mask, ==, 0x000000ff);
+
+  g_assert_cmpint (r_shift, ==, 16);
+  g_assert_cmpint (g_shift, ==,  8);
+  g_assert_cmpint (b_shift, ==,  0);
+
+  g_assert_cmpint (r_precision, ==, 8);
+  g_assert_cmpint (g_precision, ==, 8);
+  g_assert_cmpint (b_precision, ==, 8);
+}
+
+int
+main (int argc, char *argv[])
+{
+        g_test_init (&argc, &argv, NULL);
+
+        gdk_init (NULL, NULL);
+
+        g_test_bug_base ("http://bugzilla.gnome.org/");
+
+        g_test_add_func ("/visual/rgba", test_rgba_visual);
+
+        return g_test_run ();
+}