RenderCustomPaint({CustomPainter painter, CustomPainter foregroundPainter, Size preferredSize: Size.zero, RenderBox child })

Creates a render object that delegates its painting.

Source 

RenderCustomPaint({
  CustomPainter painter,
  CustomPainter foregroundPainter,
  Size preferredSize: Size.zero,
  RenderBox child,
}) : _painter = painter,
     _foregroundPainter = foregroundPainter,
     _preferredSize = preferredSize,
     super(child) {
  assert(preferredSize != null);
}