Cascade newly created windows in window manager

    }

    /** Add and display a new window based on options. */

    add(options) {

        const url = withPrefix(options.url);

    add(options, layout = 10, margin = 20, index = 850) {

        const url = this._build_url(withPrefix(options.url), { hide_panels: true, hide_masthead: true });

        const x = this.counter * margin;

        const y = (this.counter % layout) * margin;

        this.counter++;

        const boxUrl = this._build_url(url, { hide_panels: true, hide_masthead: true });

        WinBox.new({

            index: index,

            title: options.title || "Window",

            url: boxUrl,

            index: 850,

            url: url,

            x: x,

            y: y,

            onclose: () => {

                this.counter--;

            },