Added helper method to support reconfigureItems.

Author: ekazaev

ChatLayout.podspec

@@ -1,6 +1,6 @@
 Pod::Spec.new do |s|
   s.name             = 'ChatLayout'
-  s.version          = '1.3.3'
+  s.version          = '1.3.4'
   s.summary          = 'Chat UI Library. It uses custom UICollectionViewLayout to provide you full control over the presentation.'
   s.swift_version    = '5.8'
 

ChatLayout/Classes/Core/CollectionViewChatLayout.swift

@@ -205,6 +205,8 @@ public final class CollectionViewChatLayout: UICollectionViewLayout {
 
     private let _flipsHorizontallyInOppositeLayoutDirection: Bool
 
+    private var reconfigureItemsIndexPaths: [IndexPath] = []
+
     // MARK: IOS 15.1 fix flags
 
     private var needsIOS15_1IssueFix: Bool {
@@ -529,7 +531,7 @@ public final class CollectionViewChatLayout: UICollectionViewLayout {
         let newItemSize = itemSize(with: preferredMessageAttributes)
         let newInterItemSpacing = interItemSpacing(for: preferredMessageAttributes.kind, at: preferredMessageAttributes.indexPath)
         let newItemAlignment: ChatItemAlignment
-        if controller.reloadedIndexes.contains(preferredMessageAttributes.indexPath) {
+        if controller.reloadedIndexes.contains(preferredMessageAttributes.indexPath) || reconfigureItemsIndexPaths.contains(preferredMessageAttributes.indexPath) {
             newItemAlignment = alignment(for: preferredMessageAttributes.kind, at: preferredMessageAttributes.indexPath)
         } else {
             newItemAlignment = preferredMessageAttributes.alignment
@@ -604,6 +606,12 @@ public final class CollectionViewChatLayout: UICollectionViewLayout {
         return invalidationContext
     }
 
+    /// If you want to use new `UICollectionView.reconfigureItems(..)` api and expect the reconfiguration to happen animated as well
+    // - you must call this method next to the `UICollectionView` one. `UIKit` in its classic way uses private API to process it.
+    public func reconfigureItems(at indexPaths: [IndexPath]) {
+        reconfigureItemsIndexPaths = indexPaths
+    }
+
     /// Invalidates the current layout using the information in the provided context object.
     public override func invalidateLayout(with context: UICollectionViewLayoutInvalidationContext) {
         guard let collectionView else {
@@ -690,6 +698,22 @@ public final class CollectionViewChatLayout: UICollectionViewLayout {
         controller.process(changeItems: changeItems)
         state = .afterUpdate
         dontReturnAttributes = false
+
+        if let collectionView,
+           !reconfigureItemsIndexPaths.isEmpty {
+            reconfigureItemsIndexPaths.filter { collectionView.indexPathsForVisibleItems.contains($0) }.forEach { indexPath in
+
+                let cell = collectionView.cellForItem(at: indexPath)
+
+                if let originalAttributes = controller.itemAttributes(for: indexPath.itemPath, kind: .cell, at: .beforeUpdate),
+                   let preferredAttributes = cell?.preferredLayoutAttributesFitting(originalAttributes),
+                   shouldInvalidateLayout(forPreferredLayoutAttributes: preferredAttributes, withOriginalAttributes: originalAttributes) {
+                    _ = invalidationContext(forPreferredLayoutAttributes: preferredAttributes, withOriginalAttributes: originalAttributes)
+                }
+            }
+            reconfigureItemsIndexPaths = []
+        }
+
         super.prepare(forCollectionViewUpdates: updateItems)
     }