Incorrect index given on carousel:didScrollFrom:To: delegate on loop mode

[firanto]

When I implement func carousel(_ carousel: CarouselView, didScrollFrom from: Int, to: Int) of CarouselViewDelegate, in loop mode, whenever we jump from the edge of our collections, it gives wrong index.

Example, if we have 3 items, the index should be 0, 1, and 2. When scrolling forward, didScrollFrom:To: should return from 0 to 1, from 1 to 2 (and reach the end of collection). When we move forward one more time, the expected result should be from 2 to 0. But this call was giving result as from 2 to 3. This also happen when moving backward on index 0. The expected result should be from 0 to 2. And again, the call was giving from 0 to -1.

I know this happen because of extra offset cell. Maybe before calling that method, we should reassign the to in this manner:

to = to >= 0 ? to % numberOfCells : numberOfCells - 1

My take is, users only know the number of items they own. They won't give a damn about offset cells. Logically, they only know indexes of their items and looping should give correct index which they know. Not some index outside their collection.

[zhangbozhb]

@kurotsukikaitou Thanks. As you point out, it gives wrong index. from/to was use to indicate scroll direction. Assume cell number is 3. As none loop type, the current display cell is 3, and you scroll. At this point 'carouselScroll(from:3, to: 4)' or 'carouselScroll(from:3, to: 0)'. Maybe the later is more reasonable。And this may be more confused，if cell count is 2 and in loop mode。
Your idea sounds more reasonable in normal usage. Thanks your advise. It adopt in version 1.4.
This lib solution is not that good now, and i have an rough idea to improve it。Thanks.

[firanto]

Yeah. I stumble on the offset index confusion when using 'to' index to set UIPageControl selected index. Which is why I have to add that index conversion before setting page control's selected index.