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) {
  // Set up the paint object for the tooltip background
  final Paint paint = Paint()
    ..color = backgroundColor // Set the background color
    ..style = PaintingStyle.fill; // Make the background filled

  final Path path = Path();

  // Tooltip shape drawing logic based on the position
  switch (position) {
    case TooltipPosition.top:
      // Draw the rounded rectangle and arrow pointing downwards
      path.addRRect(RRect.fromRectAndRadius(
          Rect.fromLTRB(0, 0, width, height), const Radius.circular(5)));
      path.moveTo(width / 2 - 10, height); // Arrow left side
      path.lineTo(width / 2, height + 10); // Arrow tip
      path.lineTo(width / 2 + 10, height); // Arrow right side
      break;
    case TooltipPosition.bottom:
      // Draw the rounded rectangle and arrow pointing upwards
      path.addRRect(RRect.fromRectAndRadius(
          Rect.fromLTRB(0, 0, width, height), const Radius.circular(5)));
      path.moveTo(width / 2 - 10, 0); // Arrow left side
      path.lineTo(width / 2, -10); // Arrow tip
      path.lineTo(width / 2 + 10, 0); // Arrow right side
      break;
    case TooltipPosition.left:
      // Draw the rounded rectangle and arrow pointing right
      path.addRRect(RRect.fromRectAndRadius(
          Rect.fromLTRB(0, 0, width, height), const Radius.circular(5)));
      path.moveTo(width, height / 2 - 10); // Arrow top side
      path.lineTo(width + 10, height / 2); // Arrow tip
      path.lineTo(width, height / 2 + 10); // Arrow bottom side
      break;
    case TooltipPosition.right:
      // Draw the rounded rectangle and arrow pointing left
      path.addRRect(RRect.fromRectAndRadius(
          Rect.fromLTRB(0, 0, width, height), const Radius.circular(5)));
      path.moveTo(0, height / 2 - 10); // Arrow top side
      path.lineTo(-10, height / 2); // Arrow tip
      path.lineTo(0, height / 2 + 10); // Arrow bottom side
      break;
  }

  // Draw the tooltip shape on the canvas
  canvas.drawPath(path, paint);

  // Draw the tooltip text
  final TextSpan span = TextSpan(
    text: message,
    style: textStyle,
  );

  final TextPainter textPainter = TextPainter(
    text: span,
    textDirection: TextDirection.ltr, // Set the text direction
    maxLines: 2, // Limit to two lines if the text is too long
  );
  textPainter.layout(maxWidth: width - 10); // Add padding to the text

  // Paint the text on the canvas at the appropriate position
  textPainter.paint(canvas, Offset(10, (height - textPainter.height) / 2));
}