Mask mask

The calling display object is masked by the specified mask object.

By default, a Mask is applied relative to this display object. If Mask.relativeToParent is set to true, the Mask is applied relative to the parent display object.

Source 

@override
Mask get mask => _mask;
void mask=(Mask value)

Source 

set mask(Mask value) {
  _mask = value;
}