paint method Null safety

  1. @override
void paint(
  1. Canvas canvas,
  2. Rect rect,
  3. {TextDirection? textDirection,
  4. BoxShape shape = BoxShape.rectangle,
  5. BorderRadius? borderRadius}
)
override

Paints the border within the given Rect on the given Canvas.

Uniform borders are more efficient to paint than more complex borders.

You can provide a BoxShape to draw the border on. If the shape in BoxShape.circle, there is the requirement that the border isUniform.

If you specify a rectangular box shape (BoxShape.rectangle), then you may specify a BorderRadius. If a borderRadius is specified, there is the requirement that the border isUniform.

The getInnerPath and getOuterPath methods do not know about the shape and borderRadius arguments.

The textDirection argument is used to determine which of start and end map to the left and right. For TextDirection.ltr, the start is the left and the end is the right; for TextDirection.rtl, it is the reverse.

See also:

  • paintBorder, which is used if the border is not uniform.

Implementation

@override
void paint(
  Canvas canvas,
  Rect rect, {
  TextDirection? textDirection,
  BoxShape shape = BoxShape.rectangle,
  BorderRadius? borderRadius,
}) {
  if (isUniform) {
    switch (top.style) {
      case BorderStyle.none:
        return;
      case BorderStyle.solid:
        switch (shape) {
          case BoxShape.circle:
            assert(borderRadius == null, 'A borderRadius can only be given for rectangular boxes.');
            BoxBorder._paintUniformBorderWithCircle(canvas, rect, top);
            break;
          case BoxShape.rectangle:
            if (borderRadius != null) {
              BoxBorder._paintUniformBorderWithRadius(canvas, rect, top, borderRadius);
              return;
            }
            BoxBorder._paintUniformBorderWithRectangle(canvas, rect, top);
            break;
        }
        return;
    }
  }

  assert(borderRadius == null, 'A borderRadius can only be given for uniform borders.');
  assert(shape == BoxShape.rectangle, 'A border can only be drawn as a circle if it is uniform.');

  BorderSide left, right;
  assert(textDirection != null, 'Non-uniform BorderDirectional objects require a TextDirection when painting.');
  switch (textDirection!) {
    case TextDirection.rtl:
      left = end;
      right = start;
      break;
    case TextDirection.ltr:
      left = start;
      right = end;
      break;
  }
  paintBorder(canvas, rect, top: top, left: left, bottom: bottom, right: right);
}