What retrace resolves to for a trail of type T: the handle of the screen this process wrote it on top (ScreenTrail<Top>), else — a trail read back from JSON — the union of the set's screens' handles.
retrace
T
ScreenTrail<Top>
What
retraceresolves to for a trail of typeT: the handle of the screen this process wrote it on top (ScreenTrail<Top>), else — a trail read back from JSON — the union of the set's screens' handles.