[pyclutter] examples: Show how to use the ClutterX11 API

[Emmanuele Bassi <ebassi src gnome org>]

commit 6a5e78e5325aebaff046af5748623005cd370ecd
Author: Emmanuele Bassi <ebassi gnome org>
Date:   Thu Apr 30 13:17:20 2015 +0100

    examples: Show how to use the ClutterX11 API
    
    The rounded rectangle example tries to use a transparent stage.
    
    The default backend on Linux is the GDK one, if enabled, and that
    automatically uses an ARGB visual when a compositor is running; the
    X11 backend, on the other hand, needs an explicit call to enable it.

 examples/rounded-rectangle.py |    9 +++++++++
 1 files changed, 9 insertions(+), 0 deletions(-)
---
diff --git a/examples/rounded-rectangle.py b/examples/rounded-rectangle.py
index 480ccb8..eb1c062 100644
--- a/examples/rounded-rectangle.py
+++ b/examples/rounded-rectangle.py
@@ -3,6 +3,15 @@ import cairo
 from gi.repository import GObject
 from gi.repository import Clutter
 
+# Use an ARGB visual on X11; we need to do this before initializing
+# Clutter, but only if the X11 API is available
+try:
+    from gi.repository import ClutterX11
+    ClutterX11.set_use_argb_visual(True)
+except ImportError:
+    # No ClutterX11 available
+    pass
+
 # The code for the rounded rectangle drawing is taken from the
 # Cairo documentation
 def draw_content(canvas, cr, surface_width, surface_height):