[Request] Changes in one column should not affect adjacent column

[rajdhakate]

Hi, thanks for the library, works great.
I've a request, I've two column setup like below. On changing height of an item, only that column height should get updated without affecting the adjacent column. How can we do that?

Thanks again

    private func setupCollectionView() {
        let configuration = WaterfallTrueCompositionalLayout.Configuration(
            columnCount: 2,
            interItemSpacing: 0,
            contentInsetsReference: .automatic,
            itemCountProvider: { [unowned self] in
                return self.items
            },
            itemHeightProvider: { [unowned self] row, _ in
                if let currentValue = expandedIndexes[row], currentValue {
                    return self.cardHeight*2
                }
                return self.cardHeight
            }
        )

        let layout = UICollectionViewCompositionalLayout { sectionIndex, environment in
            let section = WaterfallTrueCompositionalLayout.makeLayoutSection(
                config: configuration,
                environment: environment,
                sectionIndex: sectionIndex
            )
            return section
        }
        collectionView.setCollectionViewLayout(layout, animated: true)

        collectionView.delegate = self
        collectionView.dataSource = self
    }

[eeshishko]

Hey @rajdhakate,
Thanks for the appreciation.
Regarding your needs, do I understand you right - you want to make sure items are stay in the same columns even if one of the items changed height, right? It's a very good suggestion. I've noted your request but I'm not sure when I'll have time to contribute it so I'd be very happy if you make a contribution by yourself. Here's below a basic idea how you can archive it

Current logic is simple - item is placed in the column with the lowest height:

private func columnIndex() -> Int {
        columnHeights
            .enumerated()
            .min(by: { $0.element < $1.element })?
            .offset ?? 0
    }

However, you can easily extend the API of the library by defining column behavior parameter:

public enum ColumnBehavior {
case lowestHeight
case consequently // your items will be placed like this -> [0,0], [0,1], [0,2], [1,1], [1,2], ... -> no matter what is the lowest height
case custom((index: Int) -> Int) // here you can specify closure where you will return in which column each item should go
}