_approximation);
			points_for_approximation[approximation_i] = xy;
		}
		draw_canvas("approximation_canvas");
		canvas.releasePointerCapture(e.pointerId);
	}, false);

	canvas.addEventListener('pointermove', function(e){
		if(e.buttons == 1){
			canvas_rect = canvas.getBoundingClientRect();
			points_for_approximation[approximation_i] = [e.clientX - canvas_rect.left, e.clientY - canvas_rect.top];
			draw_canvas("approximation_canvas");
		}
	}, false);

	canvas.addEventListener('pointerup', function(e){
		c