protected override void OnStyleSet(Style previous_style)
{
base.OnStyleSet(previous_style);
CheckButton check = new CheckButton();
check.EnsureStyle();
interior_focus = GtkUtilities.StyleGetProperty <bool> (check, "interior-focus", false);
focus_width = GtkUtilities.StyleGetProperty <int> (check, "focus-line-width", -1);
focus_padding = GtkUtilities.StyleGetProperty <int> (check, "focus-padding", -1);
padding = interior_focus ? focus_width + focus_padding : 0;
}