set canvas background color

gtk2_ardour/editor_canvas.cc

@@ -69,6 +69,8 @@ Editor::initialize_canvas ()
 	_track_canvas_viewport = new ArdourCanvas::GtkCanvasViewport (horizontal_adjustment, vertical_adjustment);
 	_track_canvas = _track_canvas_viewport->canvas ();
 
+        _track_canvas->set_background_color (ARDOUR_UI::config()->get_canvasvar_ArrangeBase());
+
 	/* scroll group for items that should not automatically scroll
 	 *  (e.g verbose cursor). It shares the canvas coordinate space.
 	*/