getLineLayout method

@override ({int width, int xOffset})? getLineLayout(double lineY, double lineHeight)

Gets the layout parameters (width and x-offset) for a line at a specific Y position. Returns null if the line is outside the displayable area.

Implementation

@override
({int width, int xOffset})? getLineLayout(double lineY, double lineHeight) {
  // Calculate the vertical distance from the center of the circle to the middle of the line.
  final double distFromCenter = (lineY + lineHeight / 2) - centerY;

  if (distFromCenter.abs() > radius) {
    return null; // Line is completely outside the circle.
  }

  // Use the Pythagorean theorem to calculate the half-width of the chord at this y-position.
  final double halfWidth = math.sqrt(radius * radius - distFromCenter * distFromCenter);
  final int lineWidth = (halfWidth * 2).floor();
  final int xOffset = (centerX - halfWidth).floor();

  // Avoid rendering text on very narrow lines near the top/bottom of the circle.
  if (lineWidth < fontSize) return null;

  return (width: lineWidth, xOffset: xOffset);
}