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) {
  final leftPadding = 50.0;
  final rightPadding = 20.0;
  final topPadding = 20.0;
  final bottomPadding = 40.0;
  final chartSize = Size(
    size.width - leftPadding - rightPadding,
    size.height - topPadding - bottomPadding,
  );
  final chartOffset = Offset(leftPadding, topPadding);

  if (bubbleDataSets.isEmpty) return;

  // Calculate bounds
  double minX = double.infinity;
  double maxX = double.negativeInfinity;
  double minY = double.infinity;
  double maxY = double.negativeInfinity;
  double minSize = double.infinity;
  double maxSize = double.negativeInfinity;

  for (final dataSet in bubbleDataSets) {
    for (final point in dataSet.dataPoints) {
      if (point.x < minX) minX = point.x;
      if (point.x > maxX) maxX = point.x;
      if (point.y < minY) minY = point.y;
      if (point.y > maxY) maxY = point.y;
      if (point.size < minSize) minSize = point.size;
      if (point.size > maxSize) maxSize = point.size;
    }
  }

  // Add padding to bounds
  final xRange = maxX - minX;
  final yRange = maxY - minY;
  minX -= xRange * 0.1;
  maxX += xRange * 0.1;
  minY -= yRange * 0.1;
  maxY += yRange * 0.1;

  // Calculate size range
  final sizeRange = maxSize - minSize;
  final sizeScale =
      sizeRange > 0 ? (maxBubbleSize - minBubbleSize) / sizeRange : 1.0;

  // Save canvas state
  canvas.save();
  canvas.translate(chartOffset.dx, chartOffset.dy);

  // Draw grid
  drawGrid(canvas, chartSize, minX, maxX, minY, maxY);

  // Draw axes
  drawAxes(canvas, chartSize, minX, maxX, minY, maxY);

  // Draw axis labels
  drawAxisLabels(canvas, chartSize, minX, maxX, minY, maxY);

  // Draw bubbles
  for (int datasetIndex = 0;
      datasetIndex < bubbleDataSets.length;
      datasetIndex++) {
    final dataSet = bubbleDataSets[datasetIndex];
    final color = dataSet.color;

    for (int pointIndex = 0;
        pointIndex < dataSet.dataPoints.length;
        pointIndex++) {
      final point = dataSet.dataPoints[pointIndex];

      // Validate point data to prevent NaN
      if (!point.x.isFinite || !point.y.isFinite || !point.size.isFinite) {
        continue;
      }

      final canvasPoint = pointToCanvas(
        ChartDataPoint(x: point.x, y: point.y),
        chartSize,
        minX,
        maxX,
        minY,
        maxY,
      );

      // Validate canvas point
      if (!canvasPoint.dx.isFinite || !canvasPoint.dy.isFinite) {
        continue;
      }

      // Check if this bubble is selected or hovered
      final isSelected = selectedBubble?.datasetIndex == datasetIndex &&
          selectedBubble?.elementIndex == pointIndex;
      final isHovered = hoveredBubble?.datasetIndex == datasetIndex &&
          hoveredBubble?.elementIndex == pointIndex;

      // Calculate bubble size
      final normalizedSize = sizeRange > 0
          ? minBubbleSize + (point.size - minSize) * sizeScale
          : (minBubbleSize + maxBubbleSize) / 2;
      final currentSize =
          (isSelected || isHovered ? normalizedSize * 1.2 : normalizedSize) *
              animationProgress;

      // Validate size before drawing
      if (!currentSize.isFinite || currentSize <= 0) {
        continue;
      }

      final currentColor = isSelected || isHovered
          ? color.withValues(alpha: 0.9)
          : color.withValues(alpha: 0.7);

      // Draw bubble with gradient
      if (currentSize > 0) {
        // Outer glow for selected/hovered
        if (isSelected || isHovered) {
          final glowPaint = Paint()
            ..color = currentColor.withValues(alpha: 0.2)
            ..style = PaintingStyle.fill;
          canvas.drawCircle(canvasPoint, currentSize * 1.5, glowPaint);
        }

        // Main bubble with gradient
        final gradient = RadialGradient(
          colors: [
            currentColor,
            currentColor.withValues(alpha: 0.5),
          ],
        );
        final bubblePaint = Paint()
          ..shader = gradient.createShader(
            Rect.fromCircle(
              center: canvasPoint,
              radius: currentSize,
            ),
          )
          ..style = PaintingStyle.fill;

        canvas.drawCircle(canvasPoint, currentSize, bubblePaint);

        // Border (white if selected)
        final borderPaint = Paint()
          ..color = isSelected ? Colors.white : theme.backgroundColor
          ..style = PaintingStyle.stroke
          ..strokeWidth = isSelected ? 3.0 : 2.0;
        canvas.drawCircle(canvasPoint, currentSize, borderPaint);
      }
    }
  }

  canvas.restore();
}