Added keepContentAtBottomOfVisibleArea flag

ChatLayout.podspec

@@ -1,6 +1,6 @@
 Pod::Spec.new do |s|
   s.name             = 'ChatLayout'
-  s.version          = '2.0.4'
+  s.version          = '2.0.5'
   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

@@ -52,7 +52,7 @@ open class CollectionViewChatLayout: UICollectionViewLayout {
         }
     }
 
-    /// Default `UIScrollView` behaviour is to keep content offset constant from the top edge. If this flag is set to `true`
+    /// The default `UIScrollView` behaviour is to keep content offset constant from the top edge. If this flag is set to `true`
     /// `CollectionViewChatLayout` should try to compensate batch update changes to keep the current content at the bottom of the visible
     /// part of `UICollectionView`.
     ///
@@ -61,6 +61,11 @@ open class CollectionViewChatLayout: UICollectionViewLayout {
     /// the animation starts and wont be able to compensate that change too. It should be done manually.
     public var keepContentOffsetAtBottomOnBatchUpdates: Bool = false
 
+    /// The default behavior of UICollectionView is to maintain UICollectionViewCells at the top of the visible rectangle
+    /// when the content size is smaller than the visible area. By setting the respective flag to true, this behavior can be
+    /// reversed to achieve the result like in Telegram..
+    public var keepContentAtBottomOfVisibleArea: Bool = false
+
     /// Sometimes `UIScrollView` can behave weirdly if there are too many corrections in it's `contentOffset` during the animation. Especially when content size of the `UIScrollView`
     // is getting smaller first and then expands again as the newly appearing cells sizes are being calculated. That is why `CollectionViewChatLayout`
     /// tries to process only the elements that are currently visible on the screen. But often it is not needed. This flag allows you to have fine control over this behaviour.

ChatLayout/Classes/Core/Model/StateController.swift

@@ -27,6 +27,8 @@ protocol ChatLayoutRepresentation: AnyObject {
 
     var keepContentOffsetAtBottomOnBatchUpdates: Bool { get }
 
+    var keepContentAtBottomOfVisibleArea: Bool { get }
+
     var processOnlyVisibleItemsOnAnimatedBatchUpdates: Bool { get }
 
     func numberOfItems(in section: Int) -> Int
@@ -359,6 +361,11 @@ final class StateController<Layout: ChatLayoutRepresentation> {
         if isFinal {
             offsetByCompensation(frame: &itemFrame, at: itemPath, for: state, backward: true)
         }
+        if layoutRepresentation.keepContentAtBottomOfVisibleArea == true,
+           !(kind == .header && itemPath.section == 0),
+           !isLayoutBiggerThanVisibleBounds(at: state, withFullCompensation: false, visibleBounds: visibleBounds) {
+            itemFrame.offsettingBy(dx: 0, dy: visibleBounds.height.rounded() - contentSize(for: state).height.rounded())
+        }
         return itemFrame
     }
 

Example/ChatLayout/Chat/View/ChatViewController.swift

@@ -133,6 +133,7 @@ final class ChatViewController: UIViewController {
         chatLayout.settings.additionalInsets = UIEdgeInsets(top: 8, left: 5, bottom: 8, right: 5)
         chatLayout.keepContentOffsetAtBottomOnBatchUpdates = true
         chatLayout.processOnlyVisibleItemsOnAnimatedBatchUpdates = false
+        chatLayout.keepContentAtBottomOfVisibleArea = true
 
         collectionView = UICollectionView(frame: view.frame, collectionViewLayout: chatLayout)
         view.addSubview(collectionView)
@@ -453,6 +454,10 @@ extension ChatViewController: UICollectionViewDelegate {
 
 extension ChatViewController: ChatControllerDelegate {
     func update(with sections: [Section], requiresIsolatedProcess: Bool) {
+        // if `chatLayout.keepContentAtBottomOfVisibleArea` is enabled and content size is actually smaller than the visible size - it is better to process each batch update
+        // in isolation. Example: If you insert a cell animatingly and then reload some cell - the reload animation will appear on top of the insertion animation.
+        // Basically everytime you see any animation glitches - process batch updates in isolation.
+        let requiresIsolatedProcess = chatLayout.keepContentAtBottomOfVisibleArea == true && chatLayout.collectionViewContentSize.height < chatLayout.visibleBounds.height ? true : requiresIsolatedProcess
         processUpdates(with: sections, animated: true, requiresIsolatedProcess: requiresIsolatedProcess)
     }
 

Example/Podfile.lock

@@ -1,10 +1,10 @@
 PODS:
-  - ChatLayout (2.0.3):
-    - ChatLayout/Ultimate (= 2.0.3)
-  - ChatLayout/Core (2.0.3)
-  - ChatLayout/Extras (2.0.3):
+  - ChatLayout (2.0.5):
+    - ChatLayout/Ultimate (= 2.0.5)
+  - ChatLayout/Core (2.0.5)
+  - ChatLayout/Extras (2.0.5):
     - ChatLayout/Core
-  - ChatLayout/Ultimate (2.0.3):
+  - ChatLayout/Ultimate (2.0.5):
     - ChatLayout/Core
     - ChatLayout/Extras
   - DifferenceKit (1.3.0):
@@ -35,7 +35,7 @@ EXTERNAL SOURCES:
     :path: "../"
 
 SPEC CHECKSUMS:
-  ChatLayout: 0e958d11b184b64116eb8b37009e4f1aa5b9385f
+  ChatLayout: 73e77fd1d5f3ea46dfee7045804d00116395bf04
   DifferenceKit: ab185c4d7f9cef8af3fcf593e5b387fb81e999ca
   FPSCounter: 884afec377de66637808c4f52ecc3b85a404732b
   InputBarAccessoryView: 1d7b0a672b36e370f01f264b3907ef39d03328e3

Example/Tests/MockCollectionLayout.swift

@@ -44,6 +44,8 @@ class MockCollectionLayout: ChatLayoutRepresentation, ChatLayoutDelegate {
 
     let keepContentOffsetAtBottomOnBatchUpdates: Bool = true
 
+    let keepContentAtBottomOfVisibleArea: Bool = false
+
     let processOnlyVisibleItemsOnAnimatedBatchUpdates: Bool = true
 
     func numberOfItems(in section: Int) -> Int {

docs/Classes/CellLayoutContainerView.html

@@ -21,7 +21,7 @@
     <header class="header">
       <p class="header-col header-col--primary">
         <a class="header-link" href="../index.html">
-          ChatLayout 2.0.4 Docs
+          ChatLayout 2.0.5 Docs
         </a>
          (100% documented)
       </p>
@@ -464,7 +464,7 @@ <h4>Parameters</h4>
       </article>
     </div>
     <section class="footer">
-      <p>&copy; 2024 <a class="link" href="https://github.com/ekazaev" target="_blank" rel="external noopener">Evgeny Kazaev</a>. All rights reserved. (Last updated: 2024-03-11)</p>
+      <p>&copy; 2024 <a class="link" href="https://github.com/ekazaev" target="_blank" rel="external noopener">Evgeny Kazaev</a>. All rights reserved. (Last updated: 2024-04-30)</p>
       <p>Generated by <a class="link" href="https://github.com/realm/jazzy" target="_blank" rel="external noopener">jazzy ♪♫ v0.14.4</a>, a <a class="link" href="https://realm.io" target="_blank" rel="external noopener">Realm</a> project.</p>
     </section>
   </body>

docs/Classes/ChatLayoutAttributes.html

@@ -21,7 +21,7 @@
     <header class="header">
       <p class="header-col header-col--primary">
         <a class="header-link" href="../index.html">
-          ChatLayout 2.0.4 Docs
+          ChatLayout 2.0.5 Docs
         </a>
          (100% documented)
       </p>
@@ -450,7 +450,7 @@ <h4>Declaration</h4>
       </article>
     </div>
     <section class="footer">
-      <p>&copy; 2024 <a class="link" href="https://github.com/ekazaev" target="_blank" rel="external noopener">Evgeny Kazaev</a>. All rights reserved. (Last updated: 2024-03-11)</p>
+      <p>&copy; 2024 <a class="link" href="https://github.com/ekazaev" target="_blank" rel="external noopener">Evgeny Kazaev</a>. All rights reserved. (Last updated: 2024-04-30)</p>
       <p>Generated by <a class="link" href="https://github.com/realm/jazzy" target="_blank" rel="external noopener">jazzy ♪♫ v0.14.4</a>, a <a class="link" href="https://realm.io" target="_blank" rel="external noopener">Realm</a> project.</p>
     </section>
   </body>

docs/Classes/ChatLayoutInvalidationContext.html

@@ -21,7 +21,7 @@
     <header class="header">
       <p class="header-col header-col--primary">
         <a class="header-link" href="../index.html">
-          ChatLayout 2.0.4 Docs
+          ChatLayout 2.0.5 Docs
         </a>
          (100% documented)
       </p>
@@ -208,7 +208,7 @@ <h4>Declaration</h4>
       </article>
     </div>
     <section class="footer">
-      <p>&copy; 2024 <a class="link" href="https://github.com/ekazaev" target="_blank" rel="external noopener">Evgeny Kazaev</a>. All rights reserved. (Last updated: 2024-03-11)</p>
+      <p>&copy; 2024 <a class="link" href="https://github.com/ekazaev" target="_blank" rel="external noopener">Evgeny Kazaev</a>. All rights reserved. (Last updated: 2024-04-30)</p>
       <p>Generated by <a class="link" href="https://github.com/realm/jazzy" target="_blank" rel="external noopener">jazzy ♪♫ v0.14.4</a>, a <a class="link" href="https://realm.io" target="_blank" rel="external noopener">Realm</a> project.</p>
     </section>
   </body>

docs/Classes/CollectionViewChatLayout.html

@@ -21,7 +21,7 @@
     <header class="header">
       <p class="header-col header-col--primary">
         <a class="header-link" href="../index.html">
-          ChatLayout 2.0.4 Docs
+          ChatLayout 2.0.5 Docs
         </a>
          (100% documented)
       </p>
@@ -269,7 +269,7 @@ <h4>Declaration</h4>
                     <section class="section">
                       <div class="pointer"></div>
                       <div class="abstract">
-                        <p>Default <code>UIScrollView</code> behaviour is to keep content offset constant from the top edge. If this flag is set to <code>true</code>
+                        <p>The default <code>UIScrollView</code> behaviour is to keep content offset constant from the top edge. If this flag is set to <code>true</code>
 <code>CollectionViewChatLayout</code> should try to compensate batch update changes to keep the current content at the bottom of the visible
 part of <code>UICollectionView</code>.</p>
 
@@ -289,6 +289,35 @@ <h4>Declaration</h4>
                     </section>
                   </div>
                 </li>
+                <li class="item">
+                  <div>
+                    <code>
+                    <a name="/s:10ChatLayout014CollectionViewaB0C32keepContentAtBottomOfVisibleAreaSbvp"></a>
+                    <a name="//apple_ref/swift/Property/keepContentAtBottomOfVisibleArea" class="dashAnchor"></a>
+                    <a class="token" href="#/s:10ChatLayout014CollectionViewaB0C32keepContentAtBottomOfVisibleAreaSbvp">keepContentAtBottomOfVisibleArea</a>
+                    </code>
+                  </div>
+                  <div class="height-container">
+                    <div class="pointer-container"></div>
+                    <section class="section">
+                      <div class="pointer"></div>
+                      <div class="abstract">
+                        <p>The default behavior of UICollectionView is to maintain UICollectionViewCells at the top of the visible rectangle
+when the content size is smaller than the visible area. By setting the respective flag to true, this behavior can be
+reversed to achieve the result like in Telegram..</p>
+
+                      </div>
+                      <div class="declaration">
+                        <h4>Declaration</h4>
+                        <div class="language">
+                          <p class="aside-title">Swift</p>
+                          <pre class="highlight swift"><code><span class="kd">public</span> <span class="k">var</span> <span class="nv">keepContentAtBottomOfVisibleArea</span><span class="p">:</span> <span class="kt">Bool</span></code></pre>
+
+                        </div>
+                      </div>
+                    </section>
+                  </div>
+                </li>
                 <li class="item">
                   <div>
                     <code>
@@ -1421,7 +1450,7 @@ <h4>Declaration</h4>
       </article>
     </div>
     <section class="footer">
-      <p>&copy; 2024 <a class="link" href="https://github.com/ekazaev" target="_blank" rel="external noopener">Evgeny Kazaev</a>. All rights reserved. (Last updated: 2024-03-11)</p>
+      <p>&copy; 2024 <a class="link" href="https://github.com/ekazaev" target="_blank" rel="external noopener">Evgeny Kazaev</a>. All rights reserved. (Last updated: 2024-04-30)</p>
       <p>Generated by <a class="link" href="https://github.com/realm/jazzy" target="_blank" rel="external noopener">jazzy ♪♫ v0.14.4</a>, a <a class="link" href="https://realm.io" target="_blank" rel="external noopener">Realm</a> project.</p>
     </section>
   </body>

docs/Classes/ContainerCollectionReusableView.html

@@ -21,7 +21,7 @@
     <header class="header">
       <p class="header-col header-col--primary">
         <a class="header-link" href="../index.html">
-          ChatLayout 2.0.4 Docs
+          ChatLayout 2.0.5 Docs
         </a>
          (100% documented)
       </p>
@@ -384,7 +384,7 @@ <h4>Parameters</h4>
       </article>
     </div>
     <section class="footer">
-      <p>&copy; 2024 <a class="link" href="https://github.com/ekazaev" target="_blank" rel="external noopener">Evgeny Kazaev</a>. All rights reserved. (Last updated: 2024-03-11)</p>
+      <p>&copy; 2024 <a class="link" href="https://github.com/ekazaev" target="_blank" rel="external noopener">Evgeny Kazaev</a>. All rights reserved. (Last updated: 2024-04-30)</p>
       <p>Generated by <a class="link" href="https://github.com/realm/jazzy" target="_blank" rel="external noopener">jazzy ♪♫ v0.14.4</a>, a <a class="link" href="https://realm.io" target="_blank" rel="external noopener">Realm</a> project.</p>
     </section>
   </body>

docs/Classes/ContainerCollectionViewCell.html

@@ -21,7 +21,7 @@
     <header class="header">
       <p class="header-col header-col--primary">
         <a class="header-link" href="../index.html">
-          ChatLayout 2.0.4 Docs
+          ChatLayout 2.0.5 Docs
         </a>
          (100% documented)
       </p>
@@ -384,7 +384,7 @@ <h4>Parameters</h4>
       </article>
     </div>
     <section class="footer">
-      <p>&copy; 2024 <a class="link" href="https://github.com/ekazaev" target="_blank" rel="external noopener">Evgeny Kazaev</a>. All rights reserved. (Last updated: 2024-03-11)</p>
+      <p>&copy; 2024 <a class="link" href="https://github.com/ekazaev" target="_blank" rel="external noopener">Evgeny Kazaev</a>. All rights reserved. (Last updated: 2024-04-30)</p>
       <p>Generated by <a class="link" href="https://github.com/realm/jazzy" target="_blank" rel="external noopener">jazzy ♪♫ v0.14.4</a>, a <a class="link" href="https://realm.io" target="_blank" rel="external noopener">Realm</a> project.</p>
     </section>
   </body>

docs/Classes/EdgeAligningView.html

@@ -21,7 +21,7 @@
     <header class="header">
       <p class="header-col header-col--primary">
         <a class="header-link" href="../index.html">
-          ChatLayout 2.0.4 Docs
+          ChatLayout 2.0.5 Docs
         </a>
          (100% documented)
       </p>
@@ -536,7 +536,7 @@ <h4>Declaration</h4>
       </article>
     </div>
     <section class="footer">
-      <p>&copy; 2024 <a class="link" href="https://github.com/ekazaev" target="_blank" rel="external noopener">Evgeny Kazaev</a>. All rights reserved. (Last updated: 2024-03-11)</p>
+      <p>&copy; 2024 <a class="link" href="https://github.com/ekazaev" target="_blank" rel="external noopener">Evgeny Kazaev</a>. All rights reserved. (Last updated: 2024-04-30)</p>
       <p>Generated by <a class="link" href="https://github.com/realm/jazzy" target="_blank" rel="external noopener">jazzy ♪♫ v0.14.4</a>, a <a class="link" href="https://realm.io" target="_blank" rel="external noopener">Realm</a> project.</p>
     </section>
   </body>

docs/Classes/EdgeAligningView/Edge.html

@@ -21,7 +21,7 @@
     <header class="header">
       <p class="header-col header-col--primary">
         <a class="header-link" href="../../index.html">
-          ChatLayout 2.0.4 Docs
+          ChatLayout 2.0.5 Docs
         </a>
          (100% documented)
       </p>
@@ -288,7 +288,7 @@ <h4>Declaration</h4>
       </article>
     </div>
     <section class="footer">
-      <p>&copy; 2024 <a class="link" href="https://github.com/ekazaev" target="_blank" rel="external noopener">Evgeny Kazaev</a>. All rights reserved. (Last updated: 2024-03-11)</p>
+      <p>&copy; 2024 <a class="link" href="https://github.com/ekazaev" target="_blank" rel="external noopener">Evgeny Kazaev</a>. All rights reserved. (Last updated: 2024-04-30)</p>
       <p>Generated by <a class="link" href="https://github.com/realm/jazzy" target="_blank" rel="external noopener">jazzy ♪♫ v0.14.4</a>, a <a class="link" href="https://realm.io" target="_blank" rel="external noopener">Realm</a> project.</p>
     </section>
   </body>

docs/Classes/ImageMaskedView.html

@@ -21,7 +21,7 @@
     <header class="header">
       <p class="header-col header-col--primary">
         <a class="header-link" href="../index.html">
-          ChatLayout 2.0.4 Docs
+          ChatLayout 2.0.5 Docs
         </a>
          (100% documented)
       </p>
@@ -408,7 +408,7 @@ <h4>Declaration</h4>
       </article>
     </div>
     <section class="footer">
-      <p>&copy; 2024 <a class="link" href="https://github.com/ekazaev" target="_blank" rel="external noopener">Evgeny Kazaev</a>. All rights reserved. (Last updated: 2024-03-11)</p>
+      <p>&copy; 2024 <a class="link" href="https://github.com/ekazaev" target="_blank" rel="external noopener">Evgeny Kazaev</a>. All rights reserved. (Last updated: 2024-04-30)</p>
       <p>Generated by <a class="link" href="https://github.com/realm/jazzy" target="_blank" rel="external noopener">jazzy ♪♫ v0.14.4</a>, a <a class="link" href="https://realm.io" target="_blank" rel="external noopener">Realm</a> project.</p>
     </section>
   </body>

docs/Classes/MessageContainerView.html

@@ -21,7 +21,7 @@
     <header class="header">
       <p class="header-col header-col--primary">
         <a class="header-link" href="../index.html">
-          ChatLayout 2.0.4 Docs
+          ChatLayout 2.0.5 Docs
         </a>
          (100% documented)
       </p>
@@ -354,7 +354,7 @@ <h4>Parameters</h4>
       </article>
     </div>
     <section class="footer">
-      <p>&copy; 2024 <a class="link" href="https://github.com/ekazaev" target="_blank" rel="external noopener">Evgeny Kazaev</a>. All rights reserved. (Last updated: 2024-03-11)</p>
+      <p>&copy; 2024 <a class="link" href="https://github.com/ekazaev" target="_blank" rel="external noopener">Evgeny Kazaev</a>. All rights reserved. (Last updated: 2024-04-30)</p>
       <p>Generated by <a class="link" href="https://github.com/realm/jazzy" target="_blank" rel="external noopener">jazzy ♪♫ v0.14.4</a>, a <a class="link" href="https://realm.io" target="_blank" rel="external noopener">Realm</a> project.</p>
     </section>
   </body>

docs/Classes/RoundedCornersContainerView.html

@@ -21,7 +21,7 @@
     <header class="header">
       <p class="header-col header-col--primary">
         <a class="header-link" href="../index.html">
-          ChatLayout 2.0.4 Docs
+          ChatLayout 2.0.5 Docs
         </a>
          (100% documented)
       </p>
@@ -354,7 +354,7 @@ <h4>Declaration</h4>
       </article>
     </div>
     <section class="footer">
-      <p>&copy; 2024 <a class="link" href="https://github.com/ekazaev" target="_blank" rel="external noopener">Evgeny Kazaev</a>. All rights reserved. (Last updated: 2024-03-11)</p>
+      <p>&copy; 2024 <a class="link" href="https://github.com/ekazaev" target="_blank" rel="external noopener">Evgeny Kazaev</a>. All rights reserved. (Last updated: 2024-04-30)</p>
       <p>Generated by <a class="link" href="https://github.com/realm/jazzy" target="_blank" rel="external noopener">jazzy ♪♫ v0.14.4</a>, a <a class="link" href="https://realm.io" target="_blank" rel="external noopener">Realm</a> project.</p>
     </section>
   </body>

docs/Classes/SwappingContainerView.html

@@ -21,7 +21,7 @@
     <header class="header">
       <p class="header-col header-col--primary">
         <a class="header-link" href="../index.html">
-          ChatLayout 2.0.4 Docs
+          ChatLayout 2.0.5 Docs
         </a>
          (100% documented)
       </p>
@@ -599,7 +599,7 @@ <h4>Declaration</h4>
       </article>
     </div>
     <section class="footer">
-      <p>&copy; 2024 <a class="link" href="https://github.com/ekazaev" target="_blank" rel="external noopener">Evgeny Kazaev</a>. All rights reserved. (Last updated: 2024-03-11)</p>
+      <p>&copy; 2024 <a class="link" href="https://github.com/ekazaev" target="_blank" rel="external noopener">Evgeny Kazaev</a>. All rights reserved. (Last updated: 2024-04-30)</p>
       <p>Generated by <a class="link" href="https://github.com/realm/jazzy" target="_blank" rel="external noopener">jazzy ♪♫ v0.14.4</a>, a <a class="link" href="https://realm.io" target="_blank" rel="external noopener">Realm</a> project.</p>
     </section>
   </body>