p) {
			context.moveTo(j, i)
		} else {
			context.lineTo(j, i);
		}
		old_i = i;
		the_gap = false;
	}
	context.stroke();
	context.closePath();

	context.lineWidth = 1;
	context.strokeStyle = "#444444";
	context.setLineDash([4, 4]);
	context.beginPath();

	context.moveTo(x_to_client(-4.5), y_to_client(PI/2));
	context.lineTo(x_to_client(4.5), y_to_client(PI/2));
	context.moveTo(x_to_client(-4.5), y_to_client(-PI/2));
	context.lineTo(x_to_client(4.5), y_to_client(-PI/2));
	context.moveTo(x_to_client(3), y_t