slideOut
Slides the overlay from where it was authored to to over duration, counted back from its last drawn frame.
The travel is linear. A drawn range with no end never reaches it, and a duration of zero or less skips it, so the overlay holds its authored position in both cases.
Return
An animation sliding the overlay out.
Parameters
to
Where the overlay ends, relative to where it was authored.
duration
How long the overlay takes to leave.