Pitiphong Phongpattranont

You can add a new delegate method asking for the size of the header similar to the UITableViewDelegate and add the logic in the calculateLayout method

I see that there are some unrelated code in this PR (especially the CocoaPods). Could you remove them?

Yes, you can. By having a custom subclass for the Header view for each section

What are those square? Are they a UICollectionViewCell?

I think in this case, you can have a disclosure indicator a UICollectionViewCell with another cell type with its own cell identifier and return it from the cellForItem method.

I see. I'm afraid that this library doesn't support this scenario out of the box but you can fork this project and make a change to make it support your...

You can add a new kind of supplementary view for the detail disclosure (and may also with a custom Layout Attribute) and layout it in prepareLayout method similar to https://github.com/pitiphong-p/CollectionViewShelfLayout/blob/master/CollectionViewShelfLayout/CollectionViewShelfLayout.swift#L178-L186...

Or if you set the deployment target at iOS 13 then you may try the new https://developer.apple.com/documentation/uikit/uicollectionviewcompositionallayout as presented in https://developer.apple.com/videos/play/wwdc2019/215/

The question is "How and where will we gonna do the snapping? At center or the edge? Or do we need an option for that?"

I agree with @kballard