r.bottom = r.top + y_sep * num_hori_lines;

		OverflowSafeInt64 interval_size = interval.highest + abs(interval.lowest);

		/* Where to draw the X axis. Use floating point to avoid overflowing and results of zero. */

		x_axis_offset = (int)((r.bottom - r.top) * (double)interval.highest / (double)interval_size);

		/* Draw the vertical grid lines. */

		/* Don't draw the first line, as that's where the axis will be. */

		x = r.left + x_sep;

		for (int i = 0; i < this->num_vert_lines; i++) {