class Test : Gtk.Widget {
    static construct {
        ParamSpecInt _pspec = new ParamSpecInt (
                "dummy", "dummy", "dummy",
                0, 0, 0,   // min, max, def
                ParamFlags.READWRITE
            );
        install_style_property (_pspec);
    }

    construct {
        string css = """
        * {
            -Test-dummy: 10;
        }""";
        var cssprov = new Gtk.CssProvider ();
        cssprov.load_from_data (css);
        get_style_context ().add_provider (cssprov, Gtk.STYLE_PROVIDER_PRIORITY_APPLICATION);
    }
}

void main (string? argv[]) {
    Gtk.init (ref argv);
    var wid = new Test ();
    int dummy;
    wid.style_get ("dummy", out dummy);
    print (dummy.to_string () + "\n");
}