gateDrawRect(groupIndex, gateIndex) {
        let dx = gateIndex % 2;
        let dy = Math.floor(gateIndex / 2);

        let x = Config.TOOLBOX_MARGIN_X +
            dx * Config.TOOLBOX_GATE_SPAN +
            groupIndex * Config.TOOLBOX_GROUP_SPAN;
        let y = this.top +
            (this.labelsOnTop ? Config.TOOLBOX_MARGIN_Y : 3) +
            dy * Config.TOOLBOX_GATE_SPAN;

        return new Rect(
            Math.round(x - 0.5) + 0.5,
            Math.round(y - 0.5) + 0.5,
            Config.GATE_RADIUS * 2,
            Config.GATE_RADIUS * 2);
    }
@param {!int} groupIndex
@param {!int} gateIndex
@returns {!Rect}
@private