moveTo(x, y) {
		const _x = this.pos.x;
		const _y = this.pos.y;

		this.pos.x = clamp(x, this.bounds.left, this.bounds.width);
		this.pos.y = clamp(y, this.bounds.top, this.bounds.height);

		//publish the VIEWPORT_ONCHANGE event if necessary
		if (_x !== this.pos.x || _y !== this.pos.y) {
			this.isDirty = true;
		}
	}
move the camera upper-left position to the specified coordinates
@see {@link focusOn}
@param {number} x
@param {number} y