protected override void OnStyleSet(Gtk.Style style)
{
base.OnStyleSet(style);
fill_color_a = DrawingUtilities.GdkColorToCairoColor(Style.Background(StateType.Normal));
var c = FileFind.Meshwork.GtkClient.GtkHelper.DarkenColor(Style.Background(StateType.Normal), 1);
fill_color_b = DrawingUtilities.GdkColorToCairoColor(c);
}