FlDotLineSegmentPainter

fl_dot_line_segment_painter.dart

/// This class is an implementation of a [FlDotPainter] that draws
/// a line segment with a value label above it.
class FlDotLineSegmentPainter extends FlDotPainter {
  /// Constructs a [FlDotLineSegmentPainter].
  FlDotLineSegmentPainter({
    required this.width,
    required this.height,
    required this.value,
    required this.textColor,
    this.color = Colors.blue,
    this.showText = true,
  });

  /// The color of the line segment.
  final Color color;

  /// The width of the line segment.
  final double width;

  /// The height of the line segment.
  final double height;

  /// The numerical value to display above the line segment.
  final double value;

  /// The color of the text displaying the value.
  final Color textColor;

  /// Whether to show the text label.
  final bool showText;

  /// Draws the line segment and the value label on the canvas.
  @override
  void draw(Canvas canvas, FlSpot spot, Offset offsetInCanvas) {
    // Draw the line segment
    final paint = Paint()
      ..color = color
      ..style = PaintingStyle.stroke
      ..strokeWidth = width;
    canvas.drawLine(
      Offset(offsetInCanvas.dx, offsetInCanvas.dy - height / 2),
      Offset(offsetInCanvas.dx, offsetInCanvas.dy + height / 2),
      paint,
    );

    // Draw the value label
    if (showText) {
      final textSpan = TextSpan(
            text: value.toStringAsFixed(1),
            style: TextStyle(color: textColor),
          );
      final textPainter = TextPainter(
        text: textSpan,
        textDirection: TextDirection.ltr,
      )..layout();
      textPainter.paint(
        canvas,
        Offset(
          offsetInCanvas.dx - textPainter.width / 2,
          offsetInCanvas.dy - height / 2 - textPainter.height - 5,
        ),
      );
    }
  }

  /// Returns the size of the painter area.
  @override
  Size getSize(FlSpot spot) {
    return Size(width, height);
  }

  /// Properties used for the equality check.
  @override
  List<Object?> get props => [color, width, height, value, textColor];

  /// Interpolates between two [FlDotLineSegmentPainter]s.
  @override
  FlDotPainter lerp(FlDotPainter a, FlDotPainter b, double t) {
    if (a is FlDotLineSegmentPainter && b is FlDotLineSegmentPainter) {
      return FlDotLineSegmentPainter(
        width: lerpDouble(a.width, b.width, t)!,
        height: lerpDouble(a.height, b.height, t)!,
        color: Color.lerp(a.color, b.color, t)!,
        value: lerpDouble(a.value, b.value, t)!,
        textColor: Color.lerp(a.textColor, b.textColor, t)!,
      );
    } else {
      throw Exception(
          'Cannot interpolate between different types of FlDotPainters',);
    }
  }

  /// The main color of the dot painter.
  @override
  Color get mainColor => color;
}