Add customizable accessoryView besides messageContainer

Sources/Controllers/MessagesViewController.swift

@@ -180,14 +180,17 @@ UICollectionViewDelegateFlowLayout, UICollectionViewDataSource {
         case .text, .attributedText, .emoji:
             let cell = messagesCollectionView.dequeueReusableCell(TextMessageCell.self, for: indexPath)
             cell.configure(with: message, at: indexPath, and: messagesCollectionView)
+            messagesDataSource.configCell(cell, for: message, at: indexPath)
             return cell
         case .photo, .video:
             let cell = messagesCollectionView.dequeueReusableCell(MediaMessageCell.self, for: indexPath)
             cell.configure(with: message, at: indexPath, and: messagesCollectionView)
+            messagesDataSource.configCell(cell, for: message, at: indexPath)
             return cell
         case .location:
             let cell = messagesCollectionView.dequeueReusableCell(LocationMessageCell.self, for: indexPath)
             cell.configure(with: message, at: indexPath, and: messagesCollectionView)
+            messagesDataSource.configCell(cell, for: message, at: indexPath)
             return cell
         case .custom:
             fatalError(MessageKitError.customDataUnresolvedCell)

Sources/Layout/MessageSizeCalculator.swift

@@ -68,6 +68,9 @@ open class MessageSizeCalculator: CellSizeCalculator {
 
         attributes.messageBottomLabelAlignment = messageBottomLabelAlignment(for: message)
         attributes.messageBottomLabelSize = messageBottomLabelSize(for: message, at: indexPath)
+
+        attributes.accessoryViewSize = accessoryViewSize(for: message)
+        attributes.accessoryViewPadding = accessoryViewPadding(for: message)
     }
 
     open override func sizeForItem(at indexPath: IndexPath) -> CGSize {
@@ -185,6 +188,20 @@ open class MessageSizeCalculator: CellSizeCalculator {
         return isFromCurrentSender ? outgoingMessageBottomLabelAlignment : incomingMessageBottomLabelAlignment
     }
 
+    // MARK: - Accessory View
+
+    public func accessoryViewSize(for message: MessageType) -> CGSize {
+        let layoutDelegate = messagesLayout.messagesLayoutDelegate
+        let collectionView = messagesLayout.messagesCollectionView
+        return layoutDelegate.accessoryViewSize(for: message, in: collectionView)
+    }
+
+    public func accessoryViewPadding(for message: MessageType) -> UIEdgeInsets {
+        let layoutDelegate = messagesLayout.messagesLayoutDelegate
+        let collectionView = messagesLayout.messagesCollectionView
+        return layoutDelegate.accessoryViewPadding(for: message, in: collectionView)
+    }
+
     // MARK: - MessageContainer
 
     public func messageContainerPadding(for message: MessageType) -> UIEdgeInsets {
@@ -201,7 +218,9 @@ open class MessageSizeCalculator: CellSizeCalculator {
     open func messageContainerMaxWidth(for message: MessageType) -> CGFloat {
         let avatarWidth = avatarSize(for: message).width
         let messagePadding = messageContainerPadding(for: message)
-        return messagesLayout.itemWidth - avatarWidth - messagePadding.horizontal
+        let accessoryWidth = accessoryViewSize(for: message).width
+        let accessoryPadding = accessoryViewPadding(for: message)
+        return messagesLayout.itemWidth - avatarWidth - messagePadding.horizontal - accessoryWidth - accessoryPadding.horizontal
     }
 
     // MARK: - Helpers

Sources/Layout/MessagesCollectionViewLayoutAttributes.swift

@@ -46,6 +46,9 @@ open class MessagesCollectionViewLayoutAttributes: UICollectionViewLayoutAttribu
     public var messageBottomLabelAlignment = LabelAlignment(textAlignment: .center, textInsets: .zero)
     public var messageBottomLabelSize: CGSize = .zero
 
+    public var accessoryViewSize: CGSize = .zero
+    public var accessoryViewPadding: UIEdgeInsets = .zero
+
     // MARK: - Methods
 
     open override func copy(with zone: NSZone? = nil) -> Any {
@@ -63,6 +66,8 @@ open class MessagesCollectionViewLayoutAttributes: UICollectionViewLayoutAttribu
         copy.messageTopLabelSize = messageTopLabelSize
         copy.messageBottomLabelAlignment = messageBottomLabelAlignment
         copy.messageBottomLabelSize = messageBottomLabelSize
+        copy.accessoryViewSize = accessoryViewSize
+        copy.accessoryViewPadding = accessoryViewPadding
         return copy
         // swiftlint:enable force_cast
     }
@@ -82,6 +87,8 @@ open class MessagesCollectionViewLayoutAttributes: UICollectionViewLayoutAttribu
                 && attributes.messageTopLabelSize == messageTopLabelSize
                 && attributes.messageBottomLabelAlignment == messageBottomLabelAlignment
                 && attributes.messageBottomLabelSize == messageBottomLabelSize
+                && attributes.accessoryViewSize == accessoryViewSize
+                && attributes.accessoryViewPadding == accessoryViewPadding
         } else {
             return false
         }

Sources/Protocols/MessagesDataSource.swift

@@ -93,6 +93,14 @@ public protocol MessagesDataSource: AnyObject {
     /// The default value returned by this method is `nil`.
     func messageBottomLabelAttributedText(for message: MessageType, at indexPath: IndexPath) -> NSAttributedString?
 
+    /// Provide a chance to config a cell before it's presented. e.g. to customize the accessoryView.
+    ///
+    /// - Parameters:
+    ///   - cell: The `MessageContentCell` that can be configured.
+    ///   - message: The `MessageType` that will be displayed by this cell.
+    ///   - indexPath: The `IndexPath` of the cell.
+    ///
+    func configCell(_ cell: MessageContentCell, for message: MessageType, at indexPath: IndexPath)
 }
 
 public extension MessagesDataSource {
@@ -117,4 +125,5 @@ public extension MessagesDataSource {
         return nil
     }
 
+    func configCell(_ cell: MessageCollectionViewCell, for message: MessageType, at indexPath: IndexPath) {}
 }

Sources/Protocols/MessagesLayoutDelegate.swift

@@ -81,6 +81,25 @@ public protocol MessagesLayoutDelegate: AnyObject {
     ///   The default value returned by this method is zero.
     func messageBottomLabelHeight(for message: MessageType, at indexPath: IndexPath, in messagesCollectionView: MessagesCollectionView) -> CGFloat
 
+    /// Specifies the size for the `MessageContentCell`'s accessory view.
+    ///
+    /// - Parameters:
+    ///   - message: The `MessageType` that will be displayed for this cell.
+    ///   - messagesCollectionView: The `MessagesCollectionView` in which this cell will be displayed.
+    ///
+    /// - Note:
+    ///   The default value returned by this method is zero.
+    func accessoryViewSize(for message: MessageType, in messagesCollectionView: MessagesCollectionView) -> CGSize
+
+    /// Specifies the padding for the `MessageContentCell`'s accessory view.
+    ///
+    /// - Parameters:
+    ///   - message: The `MessageType` that will be displayed for this cell.
+    ///   - messagesCollectionView: The `MessagesCollectionView` in which this cell will be displayed.
+    ///
+    /// - Note:
+    ///   The default value returned by this method is zero.
+    func accessoryViewPadding(for message: MessageType, in messagesCollectionView: MessagesCollectionView) -> UIEdgeInsets
 }
 
 public extension MessagesLayoutDelegate {
@@ -104,4 +123,12 @@ public extension MessagesLayoutDelegate {
     func messageBottomLabelHeight(for message: MessageType, at indexPath: IndexPath, in messagesCollectionView: MessagesCollectionView) -> CGFloat {
         return 0
     }
+
+    func accessoryViewSize(for message: MessageType, in messagesCollectionView: MessagesCollectionView) -> CGSize {
+        return .zero
+    }
+
+    func accessoryViewPadding(for message: MessageType, in messagesCollectionView: MessagesCollectionView) -> UIEdgeInsets {
+        return .zero
+    }
 }

Sources/Views/Cells/MessageContentCell.swift

@@ -60,6 +60,9 @@ open class MessageContentCell: MessageCollectionViewCell {
         return label
     }()
 
+    // Should only add customized subviews - don't change accessoryView itself.
+    open var accessoryView: UIView = .init()
+
     /// The `MessageCellDelegate` for the cell.
     open weak var delegate: MessageCellDelegate?
 
@@ -74,6 +77,7 @@ open class MessageContentCell: MessageCollectionViewCell {
     }
 
     open func setupSubviews() {
+        contentView.addSubview(accessoryView)
         contentView.addSubview(cellTopLabel)
         contentView.addSubview(messageTopLabel)
         contentView.addSubview(messageBottomLabel)
@@ -86,6 +90,9 @@ open class MessageContentCell: MessageCollectionViewCell {
         cellTopLabel.text = nil
         messageTopLabel.text = nil
         messageBottomLabel.text = nil
+        for view in accessoryView.subviews {
+            view.removeFromSuperview()
+        }
     }
 
     // MARK: - Configuration
@@ -99,6 +106,7 @@ open class MessageContentCell: MessageCollectionViewCell {
         layoutCellTopLabel(with: attributes)
         layoutMessageTopLabel(with: attributes)
         layoutAvatarView(with: attributes)
+        layoutAccessoryView(with: attributes)
     }
 
     /// Used to configure the cell.
@@ -270,5 +278,25 @@ open class MessageContentCell: MessageCollectionViewCell {
 
         messageBottomLabel.frame = CGRect(origin: origin, size: attributes.messageBottomLabelSize)
     }
-    
+
+    /// Positions the cell's accessory view.
+    /// - attributes: The `MessagesCollectionViewLayoutAttributes` for the cell.
+    open func layoutAccessoryView(with attributes: MessagesCollectionViewLayoutAttributes) {
+        guard attributes.accessoryViewSize != .zero else { return }
+
+        let y = (bounds.height - attributes.accessoryViewSize.height) / 2
+        var origin = CGPoint(x: 0, y: y)
+
+        // Accessory view is always on the opposite side of avatar
+        switch attributes.avatarPosition.horizontal {
+        case .cellLeading:
+            origin.x = messageContainerView.frame.maxX + attributes.accessoryViewPadding.left
+        case .cellTrailing:
+            origin.x = messageContainerView.frame.minX - attributes.accessoryViewPadding.right - attributes.accessoryViewSize.width
+        case .natural:
+            fatalError(MessageKitError.avatarPositionUnresolved)
+        }
+
+        accessoryView.frame = CGRect(origin: origin, size: attributes.accessoryViewSize)
+    }
 }