protected override void OnStyleSet (Style old_style)
{
base.OnStyleSet (old_style);
theme = Hyena.Gui.Theming.ThemeEngine.CreateTheme (this);
var light_text = Hyena.Gui.Theming.GtkTheme.GetCairoTextMidColor (this);
header_renderer.Foreground = CairoExtensions.ColorGetHex (light_text, false);
}