bool off

The availability and visibility of the display object.

Turning off a display object is similar to setting the visible property. The off property is used by third party runtimes like StageXL_GAF and StageXL_Toolkit to disable a DisplayObject without changing the visible state or removing it from the container. It's recommended that users do not use off but visible instead.

Source 

bool get off => _off;
void off=(bool value)

Source 

set off(bool value) {
  if (value is bool) _off = value;
}