addLayoutOverflow method
Implementation
void addLayoutOverflow(Rect rect) {
assert(_layoutOverflowRect != null, 'add overflow rect failed, _layoutOverflowRect not init');
_layoutOverflowRect = Rect.fromLTRB(
min(_layoutOverflowRect!.left, rect.left),
min(_layoutOverflowRect!.top, rect.top),
max(_layoutOverflowRect!.right, rect.right),
max(_layoutOverflowRect!.bottom, rect.bottom));
}