feat(ui): Add floating date divider builder. (#2422)

Co-authored-by: Sahil Kumar <[email protected]>

Author: AleksandrLarin-Ardas

packages/stream_chat_flutter/CHANGELOG.md

@@ -1,3 +1,10 @@
+## Upcoming
+
+✅ Added
+
+- Added `StreamMessageListView.floatingDateDividerBuilder` in order to specifically customize the
+  floating date divider.
+
 ## 9.18.0
 
 🐞 Fixed

packages/stream_chat_flutter/lib/src/message_list_view/message_list_view.dart

@@ -95,6 +95,7 @@ class StreamMessageListView extends StatefulWidget {
     this.threadBuilder,
     this.onThreadTap,
     this.dateDividerBuilder,
+    this.floatingDateDividerBuilder,
     // we need to use ClampingScrollPhysics to avoid the list view to bounce
     // when we are at the either end of the list view and try to use 'animateTo'
     // to animate in the same direction.
@@ -241,6 +242,12 @@ class StreamMessageListView extends StatefulWidget {
   /// Builder used to render date dividers
   final Widget Function(DateTime)? dateDividerBuilder;
 
+  /// Builder used to render floating date divider that stays on top while scrolling
+  /// the message list.
+  ///
+  /// If null, It will fall back to [dateDividerBuilder] if provided.
+  final Widget Function(DateTime)? floatingDateDividerBuilder;
+
   /// Index of an item to initially align within the viewport.
   final int? initialScrollIndex;
 
@@ -852,7 +859,10 @@ class _StreamMessageListViewState extends State<StreamMessageListView> {
               reverse: widget.reverse,
               itemPositionListener: _itemPositionListener.itemPositions,
               messages: messages,
-              dateDividerBuilder: widget.dateDividerBuilder,
+              dateDividerBuilder: switch (widget.floatingDateDividerBuilder) {
+                final builder? => builder,
+                _ => widget.dateDividerBuilder,
+              },
             ),
           ),
         if (widget.showScrollToBottom)