Jarring snap at end of interactive transition.
dillan opened this issue · comments
Yeah, I've seen that too. Wondering if its due to something changing in iOS9. I'll take a look when I get some time. Please let me know if you see this issue outside of the sample app.
I've seen it in an app I'm working on that uses TLLayoutTransitioning. I see similar behavior between iOS 8 and iOS 9. I'm doing a little experimentation to see if I can zero in on the source of the issue. If you have any suggestions for things to check I'd be happy to take a look and contribute any changes.
I took an initial look at this and found that the problem is due to a misunderstanding of how the collection view finishes a transition. TLLayoutTransitioning was built under the assumption that progress values are always within [0, 1]. However, after taking a close look, it is clear that
[self.collectionView finishInteractiveTransition]
can temporarily overshoot 1, apparently taking velocity into account. The problem arises because TLLayoutTransitioning's truncates progress values to [0, 1], resulting in various discontinuities.
I've started the work to remove the truncation, but there are some subtle details in TLTransitionLayout's
interpolation logic that need to be reworked.