paint method Null safety
- Canvas canvas,
- Rect rect,
- {TextDirection? textDirection,
- BoxShape shape = BoxShape.rectangle,
- BorderRadius? borderRadius}
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.');
assert(_strokeAlignIsUniform && top.strokeAlign == StrokeAlign.inside, 'A Border can only draw strokeAlign different than StrokeAlign.inside on uniform borders.');
final 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);
}