The handle a branch receives: the handle of its screen reached the way the
engine hands one out for a screen that was not walked to — the same type a
screen's own guard narrows the front screen to (XxxScreen.is(screen)), so
the branch's data, its actions and its checkpoint() are the screen's own,
and back is optional (a challenge screen has none).
The handle a branch receives: the handle of its screen reached the way the engine hands one out for a screen that was not walked to — the same type a screen's own guard narrows the front screen to (
XxxScreen.is(screen)), so the branch'sdata, its actions and itscheckpoint()are the screen's own, andbackis optional (a challenge screen has none).