Не работает приближение камеры на тач

function init_cb(canvas_elem, success) {

		if (!success) {
			console.log("b4w init failure");
			return;
		}
	...............................

		m_app.enable_controls(canvas_elem);

		canvas_elem.addEventListener("mousedown", main_canvas_down);
		canvas_elem.addEventListener("touchstart", main_canvas_down);

		canvas_elem.addEventListener("mouseup", main_canvas_up);
		canvas_elem.addEventListener("touchend", main_canvas_up);

		canvas_elem.addEventListener("mousemove", main_canvas_move);
		canvas_elem.addEventListener("touchmove", main_canvas_move);

	......
		load();
	}