paint method

@override void paint(Canvas canvas, Size size)

Called whenever the object needs to paint. The given Canvas has its coordinate space configured such that the origin is at the top left of the box. The area of the box is the size of the size argument.

Paint operations should remain inside the given area. Graphical operations outside the bounds may be silently ignored, clipped, or not clipped. It may sometimes be difficult to guarantee that a certain operation is inside the bounds (e.g., drawing a rectangle whose size is determined by user inputs). In that case, consider calling Canvas.clipRect at the beginning of paint so everything that follows will be guaranteed to only draw within the clipped area.

Implementations should be wary of correctly pairing any calls to Canvas.save/Canvas.saveLayer and Canvas.restore, otherwise all subsequent painting on this canvas may be affected, with potentially hilarious but confusing results.

To paint text on a Canvas, use a TextPainter.

To paint an image on a Canvas:

1. Obtain an ImageStream, for example by calling ImageProvider.resolve on an AssetImage or NetworkImage object.

2. Whenever the ImageStream's underlying ImageInfo object changes (see ImageStream.addListener), create a new instance of your custom paint delegate, giving it the new ImageInfo object.

3. In your delegate's paint method, call the Canvas.drawImage, Canvas.drawImageRect, or Canvas.drawImageNine methods to paint the ImageInfo.image object, applying the ImageInfo.scale value to obtain the correct rendering size.

Implementation

@override
void paint(Canvas canvas, Size size) {
  if (data.isEmpty) return;

  // Calculate the maximum number of bars that can fit in the width
  final maxBars = (size.width / (gap + 1)).floor();
  final density = math.min(data.length, maxBars);

  // Calculate bar width ensuring we don't exceed the canvas width
  final barWidth = size.width / density;

  // Calculate sampling interval for data
  final samplingInterval = data.length / density;

  // Set wave paint stroke width
  wavePaint.strokeWidth = math.max(1, barWidth - gap);

  // Find maximum amplitude for scaling
  final maxAmplitude = data.reduce(math.max);

  // Calculate half height for center line
  final centerY = size.height / 2;

  // Calculate maximum possible amplitude in pixels (half of available height)
  final maxPixelAmplitude = centerY;

  for (int i = 0; i < density; i++) {
    // Calculate the data index, ensuring we don't exceed array bounds
    final dataIndex =
        (i * samplingInterval).floor().clamp(0, data.length - 1);

    // Scale the amplitude to [0-maxPixelAmplitude]
    final scaledAmplitude =
        (data[dataIndex] / maxAmplitude) * maxPixelAmplitude;

    // Calculate bar position
    final barX = (i * barWidth) + (barWidth / 2);

    // Calculate top and bottom points, ensuring they stay within bounds
    final top = (centerY - scaledAmplitude).clamp(0.0, size.height);
    final bottom = (centerY + scaledAmplitude).clamp(0.0, size.height);

    // Draw only if the bar would be visible
    if (barX >= 0 && barX <= size.width) {
      canvas.drawLine(Offset(barX, centerY), Offset(barX, top), wavePaint);
      canvas.drawLine(Offset(barX, centerY), Offset(barX, bottom), wavePaint);
    }
  }
}