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) {
  // Use shape's visual properties if available, otherwise use passed values
  final effectiveFillColor = shape.fillColor ?? backgroundColor;
  final effectiveStrokeColor = shape.strokeColor ?? borderColor;
  final effectiveStrokeWidth = shape.strokeWidth ?? borderWidth;

  // Calculate the inset size
  final insetSize = Size(
    size.width - inset.left - inset.right,
    size.height - inset.top - inset.bottom,
  );

  // Build the fill path at the full inset size
  final fillPath = shape.buildPath(insetSize);
  final translatedFillPath = fillPath.shift(Offset(inset.left, inset.top));

  // Draw shadows if provided
  if (shadows != null && shadows!.isNotEmpty) {
    for (final shadow in shadows!) {
      final shadowPath = translatedFillPath.shift(shadow.offset);
      final shadowPaint = Paint()
        ..color = shadow.color
        ..maskFilter = MaskFilter.blur(BlurStyle.normal, shadow.blurRadius);
      canvas.drawPath(shadowPath, shadowPaint);
    }
  }

  // Draw the filled background
  final fillPaint = Paint()
    ..color = effectiveFillColor
    ..style = PaintingStyle.fill;
  canvas.drawPath(translatedFillPath, fillPaint);

  // Draw the border - inset by the full border width on all sides
  // The stroke extends half-width on each side, so the outer edge
  // reaches the fill edge while the entire stroke stays inside
  if (effectiveStrokeWidth > 0) {
    final halfBorder = effectiveStrokeWidth / 2;

    // Border path is smaller by full border width
    final borderSize = Size(
      insetSize.width - effectiveStrokeWidth,
      insetSize.height - effectiveStrokeWidth,
    );
    final borderPath = shape.buildPath(borderSize);

    // Position inward by half border width
    final translatedBorderPath = borderPath.shift(
      Offset(inset.left + halfBorder, inset.top + halfBorder),
    );

    final borderPaint = Paint()
      ..color = effectiveStrokeColor
      ..style = PaintingStyle.stroke
      ..strokeWidth = effectiveStrokeWidth
      ..strokeCap = StrokeCap.round
      ..strokeJoin = StrokeJoin.round;
    canvas.drawPath(translatedBorderPath, borderPaint);
  }
}