Stacked on #32379
Track the range offsets along the timeline where previous/current/next
is. This can also be specified as an option. This lets you model more
than three states along a timeline by clamping them and then updating
the "current" as you go.
It also allows specifying the "current" offset as something different
than what it was when the gesture started such as if it has to start
after scroll has already happened (such as what happens if you listen to
the "scroll" event).
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