A pointer that will trigger a tap with a secondary button has stopped contacting the screen at a particular location.
This triggers in the case of the tap gesture winning. If the tap gesture did not win, onSecondaryTapCancel is called instead.
- onSecondaryTap, a handler triggered right after this one that doesn't pass any details about the tap.
- kSecondaryButton, the button this callback responds to.
final GestureTapUpCallback? onSecondaryTapUp;