Improvement in cell reconfiguration

Author: ekazaev

ChatLayout.podspec

@@ -1,6 +1,6 @@
 Pod::Spec.new do |s|
   s.name             = 'ChatLayout'
-  s.version          = '2.0.7'
+  s.version          = '2.0.8'
   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

@@ -615,6 +615,7 @@ open class CollectionViewChatLayout: UICollectionViewLayout {
         let shouldInvalidateLayout = cachedCollectionViewSize != .some(newBounds.size) ||
             cachedCollectionViewInset != .some(adjustedContentInset) ||
             invalidationActions.contains(.shouldInvalidateOnBoundsChange)
+            || (isUserInitiatedScrolling && state == .beforeUpdate)
 
         invalidationActions.remove(.shouldInvalidateOnBoundsChange)
         return shouldInvalidateLayout
@@ -723,8 +724,13 @@ open class CollectionViewChatLayout: UICollectionViewLayout {
                     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) {
+                       let preferredAttributes = cell?.preferredLayoutAttributesFitting(originalAttributes.typedCopy()) as? ChatLayoutAttributes,
+                       let itemIdentifierBeforeUpdate = controller.itemIdentifier(for: indexPath.itemPath, kind: .cell, at: .beforeUpdate),
+                       let indexPathAfterUpdate = controller.itemPath(by: itemIdentifierBeforeUpdate, kind: .cell, at: .afterUpdate)?.indexPath,
+                       let itemAfterUpdate = controller.item(for: indexPathAfterUpdate.itemPath, kind: .cell, at: .afterUpdate),
+                       (itemAfterUpdate.size.height - preferredAttributes.size.height).rounded() != 0 {
+                        originalAttributes.indexPath = indexPathAfterUpdate
+                        preferredAttributes.indexPath = indexPathAfterUpdate
                         _ = invalidationContext(forPreferredLayoutAttributes: preferredAttributes, withOriginalAttributes: originalAttributes)
                     }
                 }

ChatLayout/Classes/Core/Model/LayoutModel.swift

@@ -110,7 +110,6 @@ final class LayoutModel<Layout: ChatLayoutRepresentation> {
 
     func itemPath(by itemId: UUID, kind: ItemKind) -> ItemPath? {
         guard let itemPathByIdentifierCache else {
-            assertionFailure("Internal inconsistency. Cache is not prepared.")
             for (sectionIndex, section) in sections.enumerated() {
                 switch kind {
                 case .header:

ChatLayout/Classes/Core/Model/StateController.swift

@@ -546,6 +546,7 @@ final class StateController<Layout: ChatLayoutRepresentation> {
         var insertedSectionsIndexesArray = [(Int, SectionModel<Layout>?)]()
 
         var reloadedItemsIndexesArray = [IndexPath]()
+        var reconfiguredItemsIndexesArray = [IndexPath]()
         var deletedItemsIndexesArray = [IndexPath]()
         var insertedItemsIndexesArray = [(IndexPath, ItemModel?)]()
 
@@ -562,9 +563,7 @@ final class StateController<Layout: ChatLayoutRepresentation> {
 
                 reloadedItemsIndexesArray.append(indexPath)
             case let .itemReconfigure(itemIndexPath: indexPath):
-                reconfiguredIndexes.insert(indexPath)
-
-                reloadedItemsIndexesArray.append(indexPath)
+                reconfiguredItemsIndexesArray.append(indexPath)
             case let .sectionDelete(sectionIndex):
                 deletedSectionsIndexes.insert(sectionIndex)
 
@@ -796,6 +795,21 @@ final class StateController<Layout: ChatLayoutRepresentation> {
             }
         }
 
+        for indexPath in reconfiguredItemsIndexesArray {
+            guard var item = item(for: indexPath.itemPath, kind: .cell, at: .beforeUpdate),
+                  let indexPathAfterUpdate = afterUpdateModel.itemPath(by: item.id, kind: .cell)?.indexPath else {
+                assertionFailure("Item at index path (\(indexPath.section) - \(indexPath.item)) does not exist.")
+                continue
+            }
+            reconfiguredIndexes.insert(indexPathAfterUpdate)
+
+            let oldHeight = item.frame.height
+            let configuration = layoutRepresentation.configuration(for: .cell, at: indexPathAfterUpdate)
+            applyConfiguration(configuration, to: &item)
+            afterUpdateModel.replaceItem(item, at: indexPathAfterUpdate)
+            visibleBoundsBeforeUpdate.offsettingBy(dx: 0, dy: item.frame.height - oldHeight)
+        }
+
         var afterUpdateModelSections = afterUpdateModel.sections
         afterUpdateModelSections.withUnsafeMutableBufferPointer { directlyMutableSections in
             for index in 0..<directlyMutableSections.count {