[pyclutter] examples: Add a GtkClutterEmbed example

[Emmanuele Bassi <ebassi src gnome org>]

commit 6b778d8783591e11412e19e205eff18e0ab9b13c
Author: Emmanuele Bassi <ebassi gnome org>
Date:   Fri May 8 18:45:25 2015 +0100

    examples: Add a GtkClutterEmbed example
    
    Using the GTK+ style machinery.

 examples/Makefile.am          |    1 +
 examples/clutter-gtk-style.py |   79 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 80 insertions(+), 0 deletions(-)
---
diff --git a/examples/Makefile.am b/examples/Makefile.am
index 33c761f..86cd8ee 100644
--- a/examples/Makefile.am
+++ b/examples/Makefile.am
@@ -1,6 +1,7 @@
 EXTRA_DIST = \
        basic-actor.py \
        canvas.py \
+       clutter-gtk-style.py \
        constraints.py \
        image-content.py \
        layout-manager.py \
diff --git a/examples/clutter-gtk-style.py b/examples/clutter-gtk-style.py
new file mode 100644
index 0000000..bfb7548
--- /dev/null
+++ b/examples/clutter-gtk-style.py
@@ -0,0 +1,79 @@
+import sys
+
+try:
+    from gi.repository import GtkClutter
+except ImportError:
+    print('GtkClutter introspection data is not installed.')
+    sys.exit(1)
+
+from gi.repository import Clutter
+from gi.repository import GLib
+from gi.repository import Gtk
+
+class StyledEmbed(GtkClutter.Embed):
+    """
+    A GtkClutterEmbed class that uses the same style of the
+    top-level window to draw its background.
+    """
+    def __init__(self):
+        GtkClutter.Embed.__init__(self)
+
+        self.connect('realize', self.on_realize)
+        self.connect('size-allocate', self.on_size_allocate)
+        self.connect('style-updated', self.on_style_changed)
+
+        self._canvas = Clutter.Canvas(width=200, height=200)
+        self._canvas.connect('draw', self.on_canvas_draw)
+
+    def on_realize(self, widget):
+        """
+        Assign the Canvas content on realization.
+        """
+        stage = self.get_stage()
+        stage.props.content = self._canvas
+
+    def on_size_allocate(self, widget, alloc):
+        """
+        Resize the Canvas when the widget receives a new size.
+        """
+        self._canvas.set_size(alloc.width, alloc.height)
+
+    def on_style_changed(self, widget):
+        """
+        Invalidate the content of the Canvas when the style
+        changes.
+        """
+        self._canvas.invalidate()
+
+    def on_canvas_draw(self, canvas, cr, width, height):
+        # We proxy the style of the top-level; if we wanted to style the
+        # GtkClutterEmbed widget directly we'd need a custom CSS style
+        # provider and a style class
+        style = self.get_toplevel().get_style_context()
+        Gtk.render_background(style, cr, 0, 0, width, height)
+        return True
+
+if __name__ == '__main__':
+    GtkClutter.init(None)
+
+    # Our top-level window
+    window = Gtk.Window(title='Test')
+    window.connect('destroy', Gtk.main_quit)
+    window.show()
+
+    # The styled GtkClutterEmbed widget
+    embed = StyledEmbed()
+    # Keep the size of the stage tied to the size of the embedding widget
+    embed.props.use_layout_size = True
+    window.add(embed)
+    embed.show()
+
+    stage = embed.get_stage()
+
+    # A simple rectangle centered on the stage
+    rect = Clutter.Actor(background_color=Clutter.Color.get_static(Clutter.StaticColor.RED))
+    rect.set_size(100, 100)
+    rect.add_constraint(Clutter.AlignConstraint(source=stage, align_axis=Clutter.AlignAxis.BOTH, factor=0.5))
+    stage.add_child(rect)
+
+    Gtk.main()