shouldRepaint method
- @override
Called whenever a new instance of the custom painter delegate class is
provided to the RenderCustomPaint object, or any time that a new
CustomPaint object is created with a new instance of the custom painter
delegate class (which amounts to the same thing, because the latter is
implemented in terms of the former).
If the new instance represents different information than the old instance, then the method should return true, otherwise it should return false.
If the method returns false, then the paint call might be optimized away.
It's possible that the paint method will get called even if shouldRepaint returns false (e.g. if an ancestor or descendant needed to be repainted). It's also possible that the paint method will get called without shouldRepaint being called at all (e.g. if the box changes size).
If a custom delegate has a particularly expensive paint function such that
repaints should be avoided as much as possible, a RepaintBoundary or
RenderRepaintBoundary (or other render object with
RenderObject.isRepaintBoundary set to true) might be helpful.
The oldDelegate argument will never be null.
Implementation
@override
bool shouldRepaint(CustomPainter oldDelegate) {
return true;
}