Merge pull request #1519 from GetStream/feat/update-spl

packages/stream_chat_flutter/CHANGELOG.md

@@ -52,6 +52,8 @@
   ),
   ```
 
+- Added `StreamMessageListView.shrinkWrap` to allow users to shrink wrap the message list view.
+
 🔄 Changed
 
 - Deprecated `MessageTheme.linkBackgroundColor` in favor of `MessageTheme.urlAttachmentBackgroundColor`.

packages/stream_chat_flutter/lib/scrollable_positioned_list/src/positioned_list.dart

@@ -11,6 +11,7 @@ import 'package:stream_chat_flutter/scrollable_positioned_list/src/indexed_key.d
 import 'package:stream_chat_flutter/scrollable_positioned_list/src/item_positions_listener.dart';
 import 'package:stream_chat_flutter/scrollable_positioned_list/src/item_positions_notifier.dart';
 import 'package:stream_chat_flutter/scrollable_positioned_list/src/scroll_view.dart';
+import 'package:stream_chat_flutter/scrollable_positioned_list/src/wrapping.dart';
 
 /// A list of widgets similar to [ListView], except scroll control
 /// and position reporting is based on index rather than pixel offset.
@@ -35,28 +36,20 @@ class PositionedList extends StatefulWidget {
     this.alignment = 0,
     this.scrollDirection = Axis.vertical,
     this.reverse = false,
+    this.shrinkWrap = false,
     this.physics,
     this.padding,
     this.cacheExtent,
     this.semanticChildCount,
-    this.findChildIndexCallback,
     this.addSemanticIndexes = true,
     this.addRepaintBoundaries = true,
     this.addAutomaticKeepAlives = true,
-    this.keyboardDismissBehavior,
+    this.findChildIndexCallback,
-  }) : assert((positionedIndex == 0) || (positionedIndex < itemCount),
+    this.keyboardDismissBehavior = ScrollViewKeyboardDismissBehavior.manual,
-            'positionedIndex cannot be 0 and must be smaller than itemCount');
+  }) : assert(
-
+          (positionedIndex == 0) || (positionedIndex < itemCount),
-  /// Called to find the new index of a child based on its key in case of
+          'positionedIndex must be 0 or a value less than itemCount',
-  /// reordering.
+        );
-  ///
-  /// If not provided, a child widget may not map to its existing [RenderObject]
-  /// when the order in which children are returned from [builder] changes.
-  /// This may result in state-loss.
-  ///
-  /// This callback should take an input [Key], and it should return the
-  /// index of the child element with that associated key, or null if not found.
-  final ChildIndexGetter? findChildIndexCallback;
 
   /// Number of items the [itemBuilder] can produce.
   final int itemCount;
@@ -98,6 +91,15 @@ class PositionedList extends StatefulWidget {
   /// See [ScrollView.reverse].
   final bool reverse;
 
+  /// {@template flutter.widgets.scroll_view.shrinkWrap}
+  /// Whether the extent of the scroll view in the [scrollDirection] should be
+  /// determined by the contents being viewed.
+  ///
+  ///  Defaults to false.
+  ///
+  /// See [ScrollView.shrinkWrap].
+  final bool shrinkWrap;
+
   /// How the scroll view should respond to user input.
   ///
   /// For example, determines how the scroll view continues to animate after the
@@ -132,9 +134,22 @@ class PositionedList extends StatefulWidget {
   /// See [SliverChildBuilderDelegate.addAutomaticKeepAlives].
   final bool addAutomaticKeepAlives;
 
-  /// [ScrollViewKeyboardDismissBehavior] the defines how this [PositionedList] will
+  /// Called to find the new index of a child based on its key in case of reordering.
-  /// dismiss the keyboard automatically.
+  ///
-  final ScrollViewKeyboardDismissBehavior? keyboardDismissBehavior;
+  /// If not provided, a child widget may not map to its existing [RenderObject]
+  /// when the order of children returned from the children builder changes.
+  /// This may result in state-loss.
+  ///
+  /// This callback should take an input [Key], and it should return the
+  /// index of the child element with that associated key, or null if not found.
+  ///
+  /// See [SliverChildBuilderDelegate.findChildIndexCallback].
+  final ChildIndexGetter? findChildIndexCallback;
+
+  /// Defines how this [ScrollView] will dismiss the keyboard automatically.
+  ///
+  /// See [ScrollView.keyboardDismissBehavior].
+  final ScrollViewKeyboardDismissBehavior keyboardDismissBehavior;
 
   @override
   State<StatefulWidget> createState() => _PositionedListState();
@@ -175,12 +190,13 @@ class _PositionedListState extends State<PositionedList> {
           anchor: widget.alignment,
           center: _centerKey,
           controller: scrollController,
-          keyboardDismissBehavior: widget.keyboardDismissBehavior,
           scrollDirection: widget.scrollDirection,
           reverse: widget.reverse,
           cacheExtent: widget.cacheExtent,
           physics: widget.physics,
+          shrinkWrap: widget.shrinkWrap,
           semanticChildCount: widget.semanticChildCount ?? widget.itemCount,
+          keyboardDismissBehavior: widget.keyboardDismissBehavior,
           slivers: <Widget>[
             if (widget.positionedIndex > 0)
               SliverPadding(
@@ -196,9 +212,9 @@ class _PositionedListState extends State<PositionedList> {
                         ? widget.positionedIndex
                         : widget.positionedIndex * 2,
                     addSemanticIndexes: false,
-                    findChildIndexCallback: widget.findChildIndexCallback,
                     addRepaintBoundaries: widget.addRepaintBoundaries,
                     addAutomaticKeepAlives: widget.addAutomaticKeepAlives,
+                    findChildIndexCallback: widget.findChildIndexCallback,
                   ),
                 ),
               ),
@@ -213,10 +229,10 @@ class _PositionedListState extends State<PositionedList> {
                           index + widget.positionedIndex * 2,
                         ),
                   childCount: widget.itemCount != 0 ? 1 : 0,
-                  findChildIndexCallback: widget.findChildIndexCallback,
                   addSemanticIndexes: false,
                   addRepaintBoundaries: widget.addRepaintBoundaries,
                   addAutomaticKeepAlives: widget.addAutomaticKeepAlives,
+                  findChildIndexCallback: widget.findChildIndexCallback,
                 ),
               ),
             ),
@@ -234,10 +250,10 @@ class _PositionedListState extends State<PositionedList> {
                     childCount: widget.separatorBuilder == null
                         ? widget.itemCount - widget.positionedIndex - 1
                         : 2 * (widget.itemCount - widget.positionedIndex - 1),
-                    findChildIndexCallback: widget.findChildIndexCallback,
                     addSemanticIndexes: false,
                     addRepaintBoundaries: widget.addRepaintBoundaries,
                     addAutomaticKeepAlives: widget.addAutomaticKeepAlives,
+                    findChildIndexCallback: widget.findChildIndexCallback,
                   ),
                 ),
               ),
@@ -319,25 +335,33 @@ class _PositionedListState extends State<PositionedList> {
     if (!updateScheduled) {
       updateScheduled = true;
       SchedulerBinding.instance.addPostFrameCallback((_) {
-        if (registeredElements.value == null) {
+        final elements = registeredElements.value;
+        if (elements == null) {
           updateScheduled = false;
           return;
         }
         final positions = <ItemPosition>[];
-        RenderViewport? viewport;
+        RenderViewportBase? viewport;
-        for (final element in registeredElements.value!) {
+        for (final element in elements) {
-          final box = element.renderObject as RenderBox?;
+          final box = element.renderObject! as RenderBox;
-          viewport ??= RenderAbstractViewport.of(box) as RenderViewport?;
+          viewport ??= RenderAbstractViewport.of(box) as RenderViewportBase?;
-          if (viewport == null || box == null) {
+          var anchor = 0.0;
-            break;
+          if (viewport is RenderViewport) {
+            anchor = viewport.anchor;
           }
-          final key = element.widget.key as IndexedKey;
+
+          if (viewport is CustomRenderViewport) {
+            anchor = viewport.anchor;
+          }
+
+          final key = element.widget.key! as IndexedKey;
+          // Skip this element if `box` has never been laid out.
+          if (!box.hasSize) continue;
           if (widget.scrollDirection == Axis.vertical) {
-            final reveal = viewport.getOffsetToReveal(box, 0).offset;
+            final reveal = viewport!.getOffsetToReveal(box, 0).offset;
             if (!reveal.isFinite) continue;
-            final itemOffset = reveal -
+            final itemOffset =
-                viewport.offset.pixels +
+                reveal - viewport.offset.pixels + anchor * viewport.size.height;
-                viewport.anchor * viewport.size.height;
             positions.add(ItemPosition(
               index: key.index,
               itemLeadingEdge: itemOffset.round() /
@@ -348,6 +372,7 @@ class _PositionedListState extends State<PositionedList> {
           } else {
             final itemOffset =
                 box.localToGlobal(Offset.zero, ancestor: viewport).dx;
+            if (!itemOffset.isFinite) continue;
             positions.add(ItemPosition(
               index: key.index,
               itemLeadingEdge: (widget.reverse

packages/stream_chat_flutter/lib/scrollable_positioned_list/src/scroll_view.dart

@@ -5,13 +5,14 @@
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';
 import 'package:stream_chat_flutter/scrollable_positioned_list/src/viewport.dart';
+import 'package:stream_chat_flutter/scrollable_positioned_list/src/wrapping.dart';
 
-/// {@template custom_scroll_view}
+/// {@template unbounded_custom_scroll_view}
-/// A version of [CustomScrollView] that does not constrict the extents
+/// A version of [CustomScrollView] that allows does not constrict the extents
 /// to be within 0 and 1. See [CustomScrollView] for more information.
 /// {@endtemplate}
 class UnboundedCustomScrollView extends CustomScrollView {
-  /// {@macro custom_scroll_view}
+  /// {@macro unbounded_custom_scroll_view}
   const UnboundedCustomScrollView({
     super.key,
     super.scrollDirection,
@@ -19,19 +20,19 @@ class UnboundedCustomScrollView extends CustomScrollView {
     super.controller,
     super.primary,
     super.physics,
-    super.shrinkWrap,
+    bool shrinkWrap = false,
     super.center,
     double anchor = 0.0,
     super.cacheExtent,
     super.slivers,
     super.semanticChildCount,
     super.dragStartBehavior,
-    ScrollViewKeyboardDismissBehavior? keyboardDismissBehavior,
+    super.keyboardDismissBehavior,
-  })  : _anchor = anchor,
+  })  : _shrinkWrap = shrinkWrap,
-        super(
+        _anchor = anchor,
-          keyboardDismissBehavior: keyboardDismissBehavior ??
+        super(shrinkWrap: false);
-              ScrollViewKeyboardDismissBehavior.manual,
+
-        );
+  final bool _shrinkWrap;
 
   // [CustomScrollView] enforces constraints on [CustomScrollView.anchor], so
   // we need our own version.
@@ -49,11 +50,14 @@ class UnboundedCustomScrollView extends CustomScrollView {
     AxisDirection axisDirection,
     List<Widget> slivers,
   ) {
-    if (shrinkWrap) {
+    if (_shrinkWrap) {
-      return ShrinkWrappingViewport(
+      return CustomShrinkWrappingViewport(
         axisDirection: axisDirection,
         offset: offset,
         slivers: slivers,
+        cacheExtent: cacheExtent,
+        center: center,
+        anchor: anchor,
       );
     }
     return UnboundedViewport(

packages/stream_chat_flutter/lib/scrollable_positioned_list/src/scrollable_positioned_list.dart

@@ -37,6 +37,7 @@ class ScrollablePositionedList extends StatefulWidget {
     required this.itemBuilder,
     super.key,
     this.itemScrollController,
+    this.shrinkWrap = false,
     ItemPositionsListener? itemPositionsListener,
     this.initialScrollIndex = 0,
     this.initialAlignment = 0,
@@ -50,7 +51,7 @@ class ScrollablePositionedList extends StatefulWidget {
     this.addRepaintBoundaries = true,
     this.minCacheExtent,
     this.findChildIndexCallback,
-    this.keyboardDismissBehavior,
+    this.keyboardDismissBehavior = ScrollViewKeyboardDismissBehavior.manual,
   })  : itemPositionsNotifier = itemPositionsListener as ItemPositionsNotifier?,
         separatorBuilder = null;
 
@@ -61,6 +62,7 @@ class ScrollablePositionedList extends StatefulWidget {
     required this.itemBuilder,
     required IndexedWidgetBuilder this.separatorBuilder,
     super.key,
+    this.shrinkWrap = false,
     this.itemScrollController,
     ItemPositionsListener? itemPositionsListener,
     this.initialScrollIndex = 0,
@@ -75,24 +77,9 @@ class ScrollablePositionedList extends StatefulWidget {
     this.addRepaintBoundaries = true,
     this.minCacheExtent,
     this.findChildIndexCallback,
-    this.keyboardDismissBehavior,
+    this.keyboardDismissBehavior = ScrollViewKeyboardDismissBehavior.manual,
   }) : itemPositionsNotifier = itemPositionsListener as ItemPositionsNotifier?;
 
-  /// Called to find the new index of a child based on its key in case of
-  /// reordering.
-  ///
-  /// If not provided, a child widget may not map to its existing [RenderObject]
-  /// when the order in which children are returned from [builder] changes.
-  /// This may result in state-loss.
-  ///
-  /// This callback should take an input [Key], and it should return the
-  /// index of the child element with that associated key, or null if not found.
-  final ChildIndexGetter? findChildIndexCallback;
-
-  /// [ScrollViewKeyboardDismissBehavior] the defines how this [PositionedList] will
-  /// dismiss the keyboard automatically.
-  final ScrollViewKeyboardDismissBehavior? keyboardDismissBehavior;
-
   /// Number of items the [itemBuilder] can produce.
   final int itemCount;
 
@@ -131,6 +118,15 @@ class ScrollablePositionedList extends StatefulWidget {
   /// See [ScrollView.reverse].
   final bool reverse;
 
+  /// {@template flutter.widgets.scroll_view.shrinkWrap}
+  /// Whether the extent of the scroll view in the [scrollDirection] should be
+  /// determined by the contents being viewed.
+  ///
+  ///  Defaults to false.
+  ///
+  /// See [ScrollView.shrinkWrap].
+  final bool shrinkWrap;
+
   /// How the scroll view should respond to user input.
   ///
   /// For example, determines how the scroll view continues to animate after the
@@ -171,6 +167,23 @@ class ScrollablePositionedList extends StatefulWidget {
   /// cache extent.
   final double? minCacheExtent;
 
+  /// Called to find the new index of a child based on its key in case of reordering.
+  ///
+  /// If not provided, a child widget may not map to its existing [RenderObject]
+  /// when the order of children returned from the children builder changes.
+  /// This may result in state-loss.
+  ///
+  /// This callback should take an input [Key], and it should return the
+  /// index of the child element with that associated key, or null if not found.
+  ///
+  /// See [SliverChildBuilderDelegate.findChildIndexCallback].
+  final ChildIndexGetter? findChildIndexCallback;
+
+  /// Defines how this [ScrollView] will dismiss the keyboard automatically.
+  ///
+  /// See [ScrollView.keyboardDismissBehavior].
+  final ScrollViewKeyboardDismissBehavior keyboardDismissBehavior;
+
   @override
   State<StatefulWidget> createState() => _ScrollablePositionedListState();
 }
@@ -233,11 +246,15 @@ class ItemScrollController {
     Curve curve = Curves.linear,
     List<double> opacityAnimationWeights = const [40, 20, 40],
   }) {
-    assert(_scrollableListState != null, '_scrollableListState cannot be null');
+    assert(
-    assert(opacityAnimationWeights.length == 3,
+      _scrollableListState != null,
-        'opacityAnimationWeights.length is not equal to 3');
+      '''ScrollController must be attached to a ScrollablePositionedList to scroll.''',
-    assert(duration > Duration.zero,
+    );
-        'duration needs to be bigger than Duration.zero');
+    assert(
+      opacityAnimationWeights.length == 3,
+      'opacityAnimationWeights must have exactly three elements.',
+    );
+    assert(duration > Duration.zero, 'Duration must be greater than zero.');
     return _scrollableListState!._scrollTo(
       index: index,
       alignment: alignment,
@@ -249,7 +266,9 @@ class ItemScrollController {
 
   void _attach(_ScrollablePositionedListState scrollableListState) {
     assert(
-        _scrollableListState == null, '_scrollableListState needs to be null');
+      _scrollableListState == null,
+      '''ScrollController must not be attached to multiple ScrollablePositionedLists.''',
+    );
     _scrollableListState = scrollableListState;
   }
 
@@ -273,11 +292,12 @@ class _ScrollablePositionedListState extends State<ScrollablePositionedList>
 
   bool _isTransitioning = false;
 
+  AnimationController? _animationController;
+
   @override
   void initState() {
     super.initState();
-    final ItemPosition? initialPosition =
+    final initialPosition = PageStorage.of(context).readState(context);
-        PageStorage.of(context).readState(context);
     primary
       ..target = initialPosition?.index ?? widget.initialScrollIndex
       ..alignment = initialPosition?.itemLeadingEdge ?? widget.initialAlignment;
@@ -301,6 +321,7 @@ class _ScrollablePositionedListState extends State<ScrollablePositionedList>
         .removeListener(_updatePositions);
     secondary.itemPositionsNotifier.itemPositions
         .removeListener(_updatePositions);
+    _animationController?.dispose();
     super.dispose();
   }
 
@@ -329,84 +350,90 @@ class _ScrollablePositionedListState extends State<ScrollablePositionedList>
   }
 
   @override
-  Widget build(BuildContext context) => LayoutBuilder(
+  Widget build(BuildContext context) {
-        builder: (context, constraints) {
+    return LayoutBuilder(
-          final cacheExtent = _cacheExtent(constraints);
+      builder: (context, constraints) {
-          return GestureDetector(
+        final cacheExtent = _cacheExtent(constraints);
-            onPanDown: (_) => _stopScroll(canceled: true),
+        return GestureDetector(
-            excludeFromSemantics: true,
+          onPanDown: (_) => _stopScroll(canceled: true),
-            child: Stack(
+          excludeFromSemantics: true,
-              children: <Widget>[
+          child: Stack(
+            children: <Widget>[
+              PostMountCallback(
+                key: primary.key,
+                callback: startAnimationCallback,
+                child: FadeTransition(
+                  opacity: ReverseAnimation(opacity),
+                  child: NotificationListener<ScrollNotification>(
+                    onNotification: (_) => _isTransitioning,
+                    child: PositionedList(
+                      itemBuilder: widget.itemBuilder,
+                      separatorBuilder: widget.separatorBuilder,
+                      itemCount: widget.itemCount,
+                      positionedIndex: primary.target,
+                      controller: primary.scrollController,
+                      itemPositionsNotifier: primary.itemPositionsNotifier,
+                      scrollDirection: widget.scrollDirection,
+                      reverse: widget.reverse,
+                      cacheExtent: cacheExtent,
+                      alignment: primary.alignment,
+                      physics: widget.physics,
+                      shrinkWrap: widget.shrinkWrap,
+                      addSemanticIndexes: widget.addSemanticIndexes,
+                      semanticChildCount: widget.semanticChildCount,
+                      padding: widget.padding,
+                      addAutomaticKeepAlives: widget.addAutomaticKeepAlives,
+                      addRepaintBoundaries: widget.addRepaintBoundaries,
+                      findChildIndexCallback: widget.findChildIndexCallback,
+                      keyboardDismissBehavior: widget.keyboardDismissBehavior,
+                    ),
+                  ),
+                ),
+              ),
+              if (_isTransitioning)
                 PostMountCallback(
-                  key: primary.key,
+                  key: secondary.key,
                   callback: startAnimationCallback,
                   child: FadeTransition(
-                    opacity: ReverseAnimation(opacity),
+                    opacity: opacity,
                     child: NotificationListener<ScrollNotification>(
-                      onNotification: (_) => _isTransitioning,
+                      onNotification: (_) => false,
                       child: PositionedList(
-                        keyboardDismissBehavior: widget.keyboardDismissBehavior,
                         itemBuilder: widget.itemBuilder,
                         separatorBuilder: widget.separatorBuilder,
                         itemCount: widget.itemCount,
-                        positionedIndex: primary.target,
+                        itemPositionsNotifier: secondary.itemPositionsNotifier,
-                        controller: primary.scrollController,
+                        positionedIndex: secondary.target,
-                        itemPositionsNotifier: primary.itemPositionsNotifier,
+                        controller: secondary.scrollController,
                         scrollDirection: widget.scrollDirection,
                         reverse: widget.reverse,
                         cacheExtent: cacheExtent,
-                        alignment: primary.alignment,
+                        alignment: secondary.alignment,
                         physics: widget.physics,
+                        shrinkWrap: widget.shrinkWrap,
                         addSemanticIndexes: widget.addSemanticIndexes,
                         semanticChildCount: widget.semanticChildCount,
                         padding: widget.padding,
                         addAutomaticKeepAlives: widget.addAutomaticKeepAlives,
                         addRepaintBoundaries: widget.addRepaintBoundaries,
                         findChildIndexCallback: widget.findChildIndexCallback,
+                        keyboardDismissBehavior: widget.keyboardDismissBehavior,
                       ),
                     ),
                   ),
                 ),
-                if (_isTransitioning)
+            ],
-                  PostMountCallback(
+          ),
-                    key: secondary.key,
+        );
-                    callback: startAnimationCallback,
+      },
-                    child: FadeTransition(
+    );
-                      opacity: opacity,
+  }
-                      child: NotificationListener<ScrollNotification>(
-                        onNotification: (_) => false,
-                        child: PositionedList(
-                          keyboardDismissBehavior:
-                              widget.keyboardDismissBehavior,
-                          itemBuilder: widget.itemBuilder,
-                          separatorBuilder: widget.separatorBuilder,
-                          itemCount: widget.itemCount,
-                          itemPositionsNotifier:
-                              secondary.itemPositionsNotifier,
-                          positionedIndex: secondary.target,
-                          controller: secondary.scrollController,
-                          scrollDirection: widget.scrollDirection,
-                          reverse: widget.reverse,
-                          cacheExtent: cacheExtent,
-                          alignment: secondary.alignment,
-                          physics: widget.physics,
-                          addSemanticIndexes: widget.addSemanticIndexes,
-                          semanticChildCount: widget.semanticChildCount,
-                          padding: widget.padding,
-                          addAutomaticKeepAlives: widget.addAutomaticKeepAlives,
-                          addRepaintBoundaries: widget.addRepaintBoundaries,
-                        ),
-                      ),
-                    ),
-                  ),
-              ],
-            ),
-          );
-        },
-      );
 
   double _cacheExtent(BoxConstraints constraints) => max(
-        constraints.maxHeight * _screenScrollCount,
+        (widget.scrollDirection == Axis.vertical
+                ? constraints.maxHeight
+                : constraints.maxWidth) *
+            _screenScrollCount,
         widget.minCacheExtent ?? 0,
       );
 
@@ -434,16 +461,19 @@ class _ScrollablePositionedListState extends State<ScrollablePositionedList>
       index = widget.itemCount - 1;
     }
     if (_isTransitioning) {
+      final scrollCompleter = Completer<void>();
       _stopScroll(canceled: true);
-      SchedulerBinding.instance.addPostFrameCallback((_) {
+      SchedulerBinding.instance.addPostFrameCallback((_) async {
-        _startScroll(
+        await _startScroll(
           index: index,
           alignment: alignment,
           duration: duration,
           curve: curve,
           opacityAnimationWeights: opacityAnimationWeights,
         );
+        scrollCompleter.complete();
       });
+      await scrollCompleter.future;
     } else {
       await _startScroll(
         index: index,
@@ -486,10 +516,11 @@ class _ScrollablePositionedListState extends State<ScrollablePositionedList>
       startAnimationCallback = () {
         SchedulerBinding.instance.addPostFrameCallback((_) {
           startAnimationCallback = () {};
-
+          _animationController?.dispose();
-          opacity.parent = _opacityAnimation(opacityAnimationWeights).animate(
+          _animationController =
-            AnimationController(vsync: this, duration: duration)..forward(),
+              AnimationController(vsync: this, duration: duration)..forward();
-          );
+          opacity.parent = _opacityAnimation(opacityAnimationWeights)
+              .animate(_animationController!);
           secondary.scrollController.jumpTo(-direction *
               (_screenScrollCount *
                       primary.scrollController.position.viewportDimension -
@@ -532,17 +563,19 @@ class _ScrollablePositionedListState extends State<ScrollablePositionedList>
       }
     }
 
-    setState(() {
+    if (mounted) {
-      if (opacity.value >= 0.5) {
+      setState(() {
-        // Secondary [ListView] is more visible than the primary; make it the
+        if (opacity.value >= 0.5) {
-        // new primary.
+          // Secondary [ListView] is more visible than the primary; make it the
-        final temp = primary;
+          // new primary.
-        primary = secondary;
+          final temp = primary;
-        secondary = temp;
+          primary = secondary;
-      }
+          secondary = temp;
-      _isTransitioning = false;
+        }
-      opacity.parent = const AlwaysStoppedAnimation<double>(0);
+        _isTransitioning = false;
-    });
+        opacity.parent = const AlwaysStoppedAnimation<double>(0);
+      });
+    }
   }
 
   Animatable<double> _opacityAnimation(List<double> opacityAnimationWeights) {

packages/stream_chat_flutter/lib/scrollable_positioned_list/src/viewport.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// ignore_for_file: lines_longer_than_80_chars
-
 import 'dart:math' as math;
 
 import 'package:flutter/rendering.dart';
@@ -15,7 +13,7 @@ import 'package:flutter/widgets.dart';
 /// Version of [Viewport] with some modifications to how extents are
 /// computed to allow scroll extents outside 0 to 1.  See [Viewport]
 /// for more information.
-/// description
+/// {@endtemplate}
 class UnboundedViewport extends Viewport {
   /// {@macro unbounded_viewport}
   UnboundedViewport({
@@ -37,15 +35,16 @@ class UnboundedViewport extends Viewport {
   double get anchor => _anchor;
 
   @override
-  RenderViewport createRenderObject(BuildContext context) =>
+  RenderViewport createRenderObject(BuildContext context) {
-      UnboundedRenderViewport(
+    return UnboundedRenderViewport(
-        axisDirection: axisDirection,
+      axisDirection: axisDirection,
-        crossAxisDirection: crossAxisDirection ??
+      crossAxisDirection: crossAxisDirection ??
-            Viewport.getDefaultCrossAxisDirection(context, axisDirection),
+          Viewport.getDefaultCrossAxisDirection(context, axisDirection),
-        anchor: anchor,
+      anchor: anchor,
-        offset: offset,
+      offset: offset,
-        cacheExtent: cacheExtent,
+      cacheExtent: cacheExtent,
-      );
+    );
+  }
 }
 
 /// A render object that is bigger on the inside.
@@ -137,14 +136,20 @@ class UnboundedRenderViewport extends RenderViewport {
   @override
   void performLayout() {
     if (center == null) {
-      assert(firstChild == null, 'firstChild cannot be null');
+      assert(
+        firstChild == null,
+        'A RenderViewport with no center render object must have no children.',
+      );
       _minScrollExtent = 0.0;
       _maxScrollExtent = 0.0;
       _hasVisualOverflow = false;
       offset.applyContentDimensions(0, 0);
       return;
     }
-    assert(center!.parent == this, 'center.parent cannot be equal to this');
+    assert(
+      center!.parent == this,
+      '''The "center" property of a RenderViewport must be a child of the viewport.''',
+    );
 
     late double mainAxisExtent;
     late double crossAxisExtent;
@@ -186,7 +191,7 @@ class UnboundedRenderViewport extends RenderViewport {
     } while (count < _maxLayoutCycles);
     assert(() {
       if (count >= _maxLayoutCycles) {
-        assert(count != 1, 'count not equal to 1');
+        assert(count != 1);
         throw FlutterError(
           'A RenderViewport exceeded its maximum number of layout cycles.\n'
           'RenderViewport render objects, during layout, can retry if either their '
@@ -207,7 +212,7 @@ class UnboundedRenderViewport extends RenderViewport {
         );
       }
       return true;
-    }(), 'count needs to be bigger than _maxLayoutCycles');
+    }());
   }
 
   double _attemptLayout(
@@ -215,11 +220,11 @@ class UnboundedRenderViewport extends RenderViewport {
     double crossAxisExtent,
     double correctedOffset,
   ) {
-    assert(!mainAxisExtent.isNaN, 'assert mainAxisExtent.isNaN');
+    assert(!mainAxisExtent.isNaN, 'The main axis extent cannot be NaN.');
-    assert(mainAxisExtent >= 0.0, 'assert mainAxisExtent >= 0.0');
+    assert(mainAxisExtent >= 0.0, 'The main axis extent cannot be negative.');
-    assert(crossAxisExtent.isFinite, 'assert crossAxisExtent.isFinite');
+    assert(crossAxisExtent.isFinite, 'The cross axis extent must be finite.');
-    assert(crossAxisExtent >= 0.0, 'assert crossAxisExtent >= 0.0');
+    assert(crossAxisExtent >= 0.0, 'The cross axis extent cannot be negative.');
-    assert(correctedOffset.isFinite, 'assert correctedOffset.isFinite');
+    assert(correctedOffset.isFinite, 'The corrected offset must be finite.');
     _minScrollExtent = 0.0;
     _maxScrollExtent = 0.0;
     _hasVisualOverflow = false;

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

@@ -71,7 +71,7 @@ enum SpacingType {
 /// A [StreamChannel] ancestor widget is required in order to provide the
 /// information about the channels.
 ///
-/// Uses a [ListView.custom] to render the list of channels.
+/// Uses a [ScrollablePositionedList] to render the list of channels.
 ///
 /// The UI is rendered based on the first ancestor of type [StreamChatTheme].
 /// Modify it to change the widget's appearance.
@@ -88,8 +88,10 @@ class StreamMessageListView extends StatefulWidget {
     this.threadBuilder,
     this.onThreadTap,
     this.dateDividerBuilder,
-    this.scrollPhysics =
+    // we need to use ClampingScrollPhysics to avoid the list view to bounce
-        const ClampingScrollPhysics(), // we need to use ClampingScrollPhysics to avoid the list view to animate and break while loading
+    // when we are at the either end of the list view and try to use 'animateTo'
+    // to animate in the same direction.
+    this.scrollPhysics = const ClampingScrollPhysics(),
     this.initialScrollIndex,
     this.initialAlignment,
     this.scrollController,
@@ -113,6 +115,7 @@ class StreamMessageListView extends StatefulWidget {
     this.unreadMessagesSeparatorBuilder,
     this.messageListController,
     this.reverse = true,
+    this.shrinkWrap = false,
     this.paginationLimit = 20,
     this.paginationLoadingIndicatorBuilder,
     this.keyboardDismissBehavior = ScrollViewKeyboardDismissBehavior.onDrag,
@@ -133,6 +136,14 @@ class StreamMessageListView extends StatefulWidget {
   /// See [ScrollView.reverse].
   final bool reverse;
 
+  /// Whether the extent of the scroll view in the [scrollDirection] should be
+  /// determined by the contents being viewed.
+  ///
+  ///  Defaults to false.
+  ///
+  /// See [ScrollView.shrinkWrap].
+  final bool shrinkWrap;
+
   /// Limit used during pagination
   final int paginationLimit;
 
@@ -548,6 +559,7 @@ class _StreamMessageListViewState extends State<StreamMessageListView> {
                   physics: widget.scrollPhysics,
                   itemScrollController: _scrollController,
                   reverse: widget.reverse,
+                  shrinkWrap: widget.shrinkWrap,
                   itemCount: itemCount,
                   findChildIndexCallback: (Key key) {
                     final indexedKey = key as IndexedKey;
@@ -555,6 +567,10 @@ class _StreamMessageListViewState extends State<StreamMessageListView> {
                     if (valueKey != null) {
                       final index = messagesIndex[valueKey.value];
                       if (index != null) {
+                        // The calculation is as follows:
+                        // * Add 2 to the index retrieved to account for the footer and the bottom loader.
+                        // * Multiply the result by 2 to account for the separators between each pair of items.
+                        // * Subtract 1 to adjust for the 0-based indexing of the list view.
                         return ((index + 2) * 2) - 1;
                       }
                     }

packages/stream_chat_flutter/test/scrollable_positioned_list/horizontal_scrollable_positioned_list_test.dart

@@ -2,13 +2,12 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-import 'dart:async';
-
 import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';
+import 'package:pedantic/pedantic.dart';
 import 'package:stream_chat_flutter/scrollable_positioned_list/scrollable_positioned_list.dart';
 
-const screenHeight = 400.0;
+const screenHeight = 100.0;
 const screenWidth = 400.0;
 const itemWidth = screenWidth / 10.0;
 const itemCount = 500;
@@ -46,6 +45,11 @@ void main() {
     );
   }
 
+  final fadeTransitionFinder = find.descendant(
+    of: find.byType(ScrollablePositionedList),
+    matching: find.byType(FadeTransition),
+  );
+
   testWidgets('List positioned with 0 at left', (WidgetTester tester) async {
     final itemPositionsListener = ItemPositionsListener.create();
     await setUpWidgetTest(tester, itemPositionsListener: itemPositionsListener);
@@ -172,7 +176,7 @@ void main() {
     await tester.pumpAndSettle();
 
     expect(tester.getTopLeft(find.text('Item 100')).dx, 0);
-    expect(tester.getBottomRight(find.text('Item 109')).dy, screenWidth);
+    expect(tester.getBottomRight(find.text('Item 109')).dy, screenHeight);
 
     expect(
         itemPositionsListener.itemPositions.value
@@ -196,6 +200,31 @@ void main() {
         1);
   });
 
+  testWidgets('Scroll to 20 without fading', (WidgetTester tester) async {
+    final itemScrollController = ItemScrollController();
+    final itemPositionsListener = ItemPositionsListener.create();
+    await setUpWidgetTest(tester,
+        itemScrollController: itemScrollController,
+        itemPositionsListener: itemPositionsListener);
+
+    var fadeTransition = tester.widget<FadeTransition>(fadeTransitionFinder);
+    final initialOpacity = fadeTransition.opacity;
+
+    unawaited(
+        itemScrollController.scrollTo(index: 20, duration: scrollDuration));
+    await tester.pump();
+    await tester.pump();
+    await tester.pump(scrollDuration ~/ 2);
+
+    fadeTransition = tester.widget<FadeTransition>(fadeTransitionFinder);
+    expect(fadeTransition.opacity, initialOpacity);
+
+    await tester.pumpAndSettle();
+
+    expect(find.text('Item 14'), findsNothing);
+    expect(find.text('Item 20'), findsOneWidget);
+  });
+
   testWidgets('padding test - centered sliver at left',
       (WidgetTester tester) async {
     final itemScrollController = ItemScrollController();

packages/stream_chat_flutter/test/scrollable_positioned_list/positioned_list_test.dart

@@ -360,4 +360,57 @@ void main() {
             .itemTrailingEdge,
         1);
   });
+
+  testWidgets('Does not crash when updated offscreen',
+      (WidgetTester tester) async {
+    late StateSetter setState;
+    var updated = false;
+
+    // There's 0 relayout boundaries in this subtree.
+    final widget = StatefulBuilder(builder: (context, stateSetter) {
+      setState = stateSetter;
+      return Positioned(
+          left: 0,
+          right: 0,
+          child: PositionedList(
+            shrinkWrap: true,
+            itemCount: 1,
+            // When `updated` becomes true this line inserts a
+            // RenderIndexedSemantics to the render tree.
+            addSemanticIndexes: updated,
+            itemBuilder: (context, index) => const SizedBox(height: itemHeight),
+          ));
+    });
+
+    await tester.pumpWidget(Directionality(
+      textDirection: TextDirection.ltr,
+      child: Overlay(
+        initialEntries: [
+          OverlayEntry(builder: (context) => widget, maintainState: true),
+        ],
+      ),
+    ));
+
+    // Insert a new opaque OverlayEntry that would prevent the first
+    // OverlayEntry from doing re-layout. Since there's no relayout boundaries
+    // in the first OverlayEntry, no dirty RenderObjects in its render subtree
+    // can update layout.
+    final newOverlay = OverlayEntry(
+      builder: (context) => const SizedBox.expand(),
+      opaque: true,
+    );
+    tester.state<OverlayState>(find.byType(Overlay)).insert(newOverlay);
+    await tester.pump();
+
+    // Update the list item's render tree. A new RenderObjectElement is
+    // inflated, registeredElement.renderObject will point to this new
+    // RenderObjectElement's RenderObject (RenderIndexedSemantics), which has
+    // never been laid out.
+    setState(() {
+      updated = true;
+    });
+
+    await tester.pump();
+    expect(tester.takeException(), isNull);
+  });
 }

packages/stream_chat_flutter/test/scrollable_positioned_list/reversed_scrollable_positioned_list_test.dart

@@ -2,10 +2,9 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-import 'dart:async';
-
 import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';
+import 'package:pedantic/pedantic.dart';
 import 'package:stream_chat_flutter/scrollable_positioned_list/scrollable_positioned_list.dart';
 
 const screenHeight = 400.0;

packages/stream_chat_flutter/test/scrollable_positioned_list/scrollable_positioned_list_test.dart

@@ -2,12 +2,12 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-import 'dart:async';
 import 'dart:math';
 
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter_test/flutter_test.dart';
+import 'package:pedantic/pedantic.dart';
 import 'package:stream_chat_flutter/scrollable_positioned_list/scrollable_positioned_list.dart';
 import 'package:stream_chat_flutter/scrollable_positioned_list/src/scroll_view.dart';
 
@@ -48,8 +48,10 @@ void main() {
           itemCount: itemCount,
           itemScrollController: itemScrollController,
           itemBuilder: (context, index) {
-            assert(index >= 0 && index <= itemCount - 1,
+            assert(
-                '''index needs to be bigger or equal to 0 and smallert than itemCount -1''');
+              index >= 0 && index <= itemCount - 1,
+              'index must be in the range of 0 to itemCount - 1',
+            );
             return SizedBox(
               height:
                   variableHeight ? (itemHeight + (index % 13) * 5) : itemHeight,
@@ -71,6 +73,11 @@ void main() {
     );
   }
 
+  final fadeTransitionFinder = find.descendant(
+    of: find.byType(ScrollablePositionedList),
+    matching: find.byType(FadeTransition),
+  );
+
   testWidgets('List positioned with 0 at top', (WidgetTester tester) async {
     final itemPositionsListener = ItemPositionsListener.create();
     await setUpWidgetTest(tester, itemPositionsListener: itemPositionsListener);
@@ -394,11 +401,7 @@ void main() {
         itemScrollController: itemScrollController,
         itemPositionsListener: itemPositionsListener);
 
-    var fadeTransition = tester.widget<FadeTransition>(find
+    var fadeTransition = tester.widget<FadeTransition>(fadeTransitionFinder);
-        .descendant(
-            of: find.byType(ScrollablePositionedList),
-            matching: find.byType(FadeTransition))
-        .last);
     final initialOpacity = fadeTransition.opacity;
 
     unawaited(
@@ -407,11 +410,7 @@ void main() {
     await tester.pump();
     await tester.pump(scrollDuration ~/ 2);
 
-    fadeTransition = tester.widget<FadeTransition>(find
+    fadeTransition = tester.widget<FadeTransition>(fadeTransitionFinder);
-        .descendant(
-            of: find.byType(ScrollablePositionedList),
-            matching: find.byType(FadeTransition))
-        .last);
     expect(fadeTransition.opacity, initialOpacity);
 
     await tester.pumpAndSettle();
@@ -456,10 +455,6 @@ void main() {
     final itemScrollController = ItemScrollController();
     await setUpWidgetTest(tester, itemScrollController: itemScrollController);
 
-    final fadeTransitionFinder = find.descendant(
-        of: find.byType(ScrollablePositionedList),
-        matching: find.byType(FadeTransition));
-
     unawaited(
         itemScrollController.scrollTo(index: 100, duration: scrollDuration));
     await tester.pump();
@@ -533,26 +528,14 @@ void main() {
     await tester.pump();
     await tester.pump();
     expect(
-        tester
+      tester.widget<FadeTransition>(fadeTransitionFinder.last).opacity.value,
-            .widget<FadeTransition>(find
+      closeTo(0, 0.01),
-                .descendant(
+    );
-                    of: find.byType(ScrollablePositionedList),
-                    matching: find.byType(FadeTransition))
-                .last)
-            .opacity
-            .value,
-        closeTo(0, 0.01));
     await tester.pump(scrollDuration + scrollDurationTolerance);
     expect(
-        tester
+      tester.widget<FadeTransition>(fadeTransitionFinder.last).opacity.value,
-            .widget<FadeTransition>(find
+      closeTo(1, 0.01),
-                .descendant(
+    );
-                    of: find.byType(ScrollablePositionedList),
-                    matching: find.byType(FadeTransition))
-                .last)
-            .opacity
-            .value,
-        closeTo(1, 0.01));
 
     expect(find.text('Item 0'), findsOneWidget);
     expect(tester.getTopLeft(find.text('Item 0')).dy, 0);
@@ -610,15 +593,9 @@ void main() {
     expect(tester.getTopLeft(find.text('Item 10')).dy, 0);
     expect(tester.getBottomLeft(find.text('Item 19')).dy, screenHeight);
     expect(
-        tester
+      tester.widget<FadeTransition>(fadeTransitionFinder.last).opacity.value,
-            .widget<FadeTransition>(find
+      closeTo(0.5, 0.01),
-                .descendant(
+    );
-                    of: find.byType(ScrollablePositionedList),
-                    matching: find.byType(FadeTransition))
-                .last)
-            .opacity
-            .value,
-        closeTo(0.5, 0.01));
 
     await tester.pumpAndSettle();
   });
@@ -899,11 +876,7 @@ void main() {
     await tester.pump();
 
     expect(tester.getTopLeft(find.text('Item 9')).dy, 0);
-    final fadeTransition = tester.widget<FadeTransition>(find
+    final fadeTransition = tester.widget<FadeTransition>(fadeTransitionFinder);
-        .descendant(
-            of: find.byType(ScrollablePositionedList),
-            matching: find.byType(FadeTransition))
-        .last);
     expect(fadeTransition.opacity.value, 1.0);
 
     await tester.pumpAndSettle();
@@ -923,21 +896,12 @@ void main() {
     await tester.pump();
 
     expect(tester.getTopLeft(find.text('Item 10')).dy, 0);
-    final fadeTransition = tester.widget<FadeTransition>(find
+    final fadeTransition = tester.widget<FadeTransition>(fadeTransitionFinder);
-        .descendant(
-            of: find.byType(ScrollablePositionedList),
-            matching: find.byType(FadeTransition))
-        .last);
     expect(fadeTransition.opacity.value, 1.0);
 
     await tester.pumpAndSettle();
   });
 
-  final fadeTransitionFinder = find.descendant(
-    of: find.byType(ScrollablePositionedList),
-    matching: find.byType(FadeTransition),
-  );
-
   testWidgets('Scroll to 0 stop before half way', (WidgetTester tester) async {
     final itemScrollController = ItemScrollController();
     await setUpWidgetTest(tester, itemScrollController: itemScrollController);
@@ -1022,14 +986,13 @@ void main() {
         itemScrollController.scrollTo(index: 0, duration: scrollDuration));
     await tester.pump();
     await tester.pump();
-    await tester.pump(scrollDuration ~/ 2 + scrollDuration ~/ 20);
+    await tester.pump(scrollDuration ~/ 2);
 
     await tester.tap(find.byType(ScrollablePositionedList));
     await tester.pump();
 
-    expect(tester.getTopLeft(find.text('Item 9')).dy, closeTo(0, tolerance));
+    expect(tester.getTopLeft(find.text('Item 90')).dy, 0);
-    final fadeTransition = tester.widget<FadeTransition>(fadeTransitionFinder);
+    expect(fadeTransitionFinder, findsNWidgets(1));
-    expect(fadeTransition.opacity.value, 1.0);
 
     await tester.pumpAndSettle();
   });
@@ -1098,6 +1061,34 @@ void main() {
     expect(find.text('Item 100'), findsNothing);
   });
 
+  testWidgets("Second scroll future doesn't complete until scroll is done",
+      (WidgetTester tester) async {
+    final itemScrollController = ItemScrollController();
+    await setUpWidgetTest(tester, itemScrollController: itemScrollController);
+
+    unawaited(
+        itemScrollController.scrollTo(index: 100, duration: scrollDuration));
+    await tester.pump();
+    await tester.pump();
+    await tester.pump(scrollDuration ~/ 2);
+
+    final scrollFuture2 =
+        itemScrollController.scrollTo(index: 250, duration: scrollDuration);
+
+    var futureComplete = false;
+    unawaited(scrollFuture2.then((_) => futureComplete = true));
+
+    await tester.pump();
+    await tester.pump();
+    await tester.pump(scrollDuration ~/ 2);
+
+    expect(futureComplete, isFalse);
+
+    await tester.pumpAndSettle();
+
+    expect(futureComplete, isTrue);
+  });
+
   testWidgets('Scroll to 250, scroll to 100, scroll to 0 half way',
       (WidgetTester tester) async {
     final itemScrollController = ItemScrollController();
@@ -1145,34 +1136,35 @@ void main() {
   }, skip: true);
 
   testWidgets(
-      '''Jump to 400 at bottom, manually scroll, scroll to 100 at bottom and back''',
+    'Jump to 400 at bottom, manually scroll, scroll to 100 at bottom and back',
-      (WidgetTester tester) async {
+    (WidgetTester tester) async {
-    final itemScrollController = ItemScrollController();
+      final itemScrollController = ItemScrollController();
-    final itemPositionsListener = ItemPositionsListener.create();
+      final itemPositionsListener = ItemPositionsListener.create();
-    await setUpWidgetTest(tester,
+      await setUpWidgetTest(tester,
-        itemScrollController: itemScrollController,
+          itemScrollController: itemScrollController,
-        itemPositionsListener: itemPositionsListener);
+          itemPositionsListener: itemPositionsListener);
 
-    itemScrollController.jumpTo(index: 400, alignment: 1);
+      itemScrollController.jumpTo(index: 400, alignment: 1);
-    await tester.pumpAndSettle();
+      await tester.pumpAndSettle();
 
-    final listFinder = find.byType(ScrollablePositionedList);
+      final listFinder = find.byType(ScrollablePositionedList);
 
-    await tester.drag(listFinder, const Offset(0, -screenHeight));
+      await tester.drag(listFinder, const Offset(0, -screenHeight));
-    await tester.pumpAndSettle();
+      await tester.pumpAndSettle();
 
-    unawaited(itemScrollController.scrollTo(
+      unawaited(itemScrollController.scrollTo(
-        index: 100, alignment: 1, duration: scrollDuration));
+          index: 100, alignment: 1, duration: scrollDuration));
-    await tester.pumpAndSettle();
+      await tester.pumpAndSettle();
 
-    unawaited(itemScrollController.scrollTo(
+      unawaited(itemScrollController.scrollTo(
-        index: 400, alignment: 1, duration: scrollDuration));
+          index: 400, alignment: 1, duration: scrollDuration));
-    await tester.pumpAndSettle();
+      await tester.pumpAndSettle();
 
-    final itemFinder = find.text('Item 399');
+      final itemFinder = find.text('Item 399');
-    expect(itemFinder, findsOneWidget);
+      expect(itemFinder, findsOneWidget);
-    expect(tester.getBottomLeft(itemFinder).dy, screenHeight);
+      expect(tester.getBottomLeft(itemFinder).dy, screenHeight);
-  });
+    },
+  );
 
   testWidgets('physics', (WidgetTester tester) async {
     final itemScrollController = ItemScrollController();
@@ -1664,70 +1656,71 @@ void main() {
   });
 
   testWidgets(
-      '''Maintain programmatic and user position (9 half way off top) in page view''',
+    'Maintain programmatic and user position (9 half way off top) in page view',
-      (WidgetTester tester) async {
+    (WidgetTester tester) async {
-    final itemPositionsListener = ItemPositionsListener.create();
+      final itemPositionsListener = ItemPositionsListener.create();
-    final itemScrollController = ItemScrollController();
+      final itemScrollController = ItemScrollController();
 
-    tester.binding.window.devicePixelRatioTestValue = 1.0;
+      tester.binding.window.devicePixelRatioTestValue = 1.0;
-    tester.binding.window.physicalSizeTestValue =
+      tester.binding.window.physicalSizeTestValue =
-        const Size(screenWidth, screenHeight);
+          const Size(screenWidth, screenHeight);
 
-    await tester.pumpWidget(
+      await tester.pumpWidget(
-      MaterialApp(
+        MaterialApp(
-        home: PageView(
+          home: PageView(
-          children: [
+            children: [
-            KeyedSubtree(
+              KeyedSubtree(
-              key: const PageStorageKey('key'),
+                key: const PageStorageKey('key'),
-              child: ScrollablePositionedList.builder(
+                child: ScrollablePositionedList.builder(
-                itemCount: defaultItemCount,
+                  itemCount: defaultItemCount,
-                itemScrollController: itemScrollController,
+                  itemScrollController: itemScrollController,
-                itemBuilder: (context, index) => SizedBox(
+                  itemBuilder: (context, index) => SizedBox(
-                  height: itemHeight,
+                    height: itemHeight,
-                  child: Text('Item $index'),
+                    child: Text('Item $index'),
+                  ),
+                  itemPositionsListener: itemPositionsListener,
                 ),
-                itemPositionsListener: itemPositionsListener,
               ),
-            ),
+              const Center(
-            const Center(
+                child: Text('Test'),
-              child: Text('Test'),
+              )
-            )
+            ],
-          ],
+          ),
         ),
-      ),
+      );
-    );
 
-    itemScrollController.jumpTo(index: 9);
+      itemScrollController.jumpTo(index: 9);
-    await tester.pump();
+      await tester.pump();
 
-    expect(tester.getBottomRight(find.text('Item 9')).dy, itemHeight);
+      expect(tester.getBottomRight(find.text('Item 9')).dy, itemHeight);
 
-    await tester.drag(
+      await tester.drag(
-        find.byType(ScrollablePositionedList), const Offset(0, -itemHeight));
+          find.byType(ScrollablePositionedList), const Offset(0, -itemHeight));
-    await tester.pumpAndSettle();
+      await tester.pumpAndSettle();
 
-    final item9Bottom = tester.getBottomRight(find.text('Item 9')).dy;
+      final item9Bottom = tester.getBottomRight(find.text('Item 9')).dy;
-    expect(item9Bottom, lessThan(itemHeight));
+      expect(item9Bottom, lessThan(itemHeight));
 
-    await tester.drag(find.byType(PageView), const Offset(-500, 0));
+      await tester.drag(find.byType(PageView), const Offset(-500, 0));
-    await tester.pumpAndSettle();
+      await tester.pumpAndSettle();
 
-    await tester.drag(find.byType(PageView), const Offset(500, 0));
+      await tester.drag(find.byType(PageView), const Offset(500, 0));
-    await tester.pumpAndSettle();
+      await tester.pumpAndSettle();
 
-    expect(tester.getBottomRight(find.text('Item 9')).dy, item9Bottom);
+      expect(tester.getBottomRight(find.text('Item 9')).dy, item9Bottom);
 
-    expect(
+      expect(
-        itemPositionsListener.itemPositions.value
+          itemPositionsListener.itemPositions.value
-            .firstWhere((position) => position.index == 9)
+              .firstWhere((position) => position.index == 9)
-            .itemLeadingEdge,
+              .itemLeadingEdge,
-        -(itemHeight / screenHeight) / 2);
+          -(itemHeight / screenHeight) / 2);
-    expect(
+      expect(
-        itemPositionsListener.itemPositions.value
+          itemPositionsListener.itemPositions.value
-            .firstWhere((position) => position.index == 9)
+              .firstWhere((position) => position.index == 9)
-            .itemTrailingEdge,
+              .itemTrailingEdge,
-        (itemHeight / screenHeight) / 2);
+          (itemHeight / screenHeight) / 2);
-  });
+    },
+  );
 
   testWidgets('List with no items', (WidgetTester tester) async {
     final itemScrollController = ItemScrollController();
@@ -1751,21 +1744,24 @@ void main() {
       MaterialApp(
         home: ValueListenableBuilder<int>(
           valueListenable: itemCount,
-          builder: (context, itemCount, child) =>
+          builder: (context, itemCount, child) {
-              ScrollablePositionedList.builder(
+            return ScrollablePositionedList.builder(
-            initialScrollIndex: min(100, itemCount),
+              initialScrollIndex: min(100, itemCount),
-            itemCount: itemCount,
+              itemCount: itemCount,
-            itemScrollController: itemScrollController,
+              itemScrollController: itemScrollController,
-            itemPositionsListener: itemPositionsListener,
+              itemPositionsListener: itemPositionsListener,
-            itemBuilder: (context, index) {
+              itemBuilder: (context, index) {
-              assert(index >= 0 && index <= itemCount - 1,
+                assert(
-                  'index not bigger than 0 and smaller than itemCount - 1');
+                  index >= 0 && index <= itemCount - 1,
-              return SizedBox(
+                  'index must be in the range of 0 to itemCount - 1',
-                height: itemHeight,
+                );
-                child: Text('Item $index'),
+                return SizedBox(
-              );
+                  height: itemHeight,
-            },
+                  child: Text('Item $index'),
-          ),
+                );
+              },
+            );
+          },
         ),
       ),
     );
@@ -1795,19 +1791,22 @@ void main() {
       MaterialApp(
         home: ValueListenableBuilder<int>(
           valueListenable: itemCount,
-          builder: (context, itemCount, child) =>
+          builder: (context, itemCount, child) {
-              ScrollablePositionedList.builder(
+            return ScrollablePositionedList.builder(
-            initialScrollIndex: min(100, itemCount - 1),
+              initialScrollIndex: min(100, itemCount - 1),
-            itemCount: itemCount,
+              itemCount: itemCount,
-            itemBuilder: (context, index) {
+              itemBuilder: (context, index) {
-              assert(index >= 0 && index <= itemCount - 1,
+                assert(
-                  'index not bigger than 0 and smaller than itemCount -1');
+                  index >= 0 && index <= itemCount - 1,
-              return SizedBox(
+                  'index must be in the range of 0 to itemCount - 1',
-                height: itemHeight,
+                );
-                child: Text('Item $index'),
+                return SizedBox(
-              );
+                  height: itemHeight,
-            },
+                  child: Text('Item $index'),
-          ),
+                );
+              },
+            );
+          },
         ),
       ),
     );
@@ -1834,19 +1833,22 @@ void main() {
       MaterialApp(
         home: ValueListenableBuilder<int>(
           valueListenable: itemCount,
-          builder: (context, itemCount, child) =>
+          builder: (context, itemCount, child) {
-              ScrollablePositionedList.builder(
+            return ScrollablePositionedList.builder(
-            initialScrollIndex: itemCount - 1,
+              initialScrollIndex: itemCount - 1,
-            itemCount: itemCount,
+              itemCount: itemCount,
-            itemBuilder: (context, index) {
+              itemBuilder: (context, index) {
-              assert(index >= 0 && index <= itemCount - 1,
+                assert(
-                  'index not bigger than 0 and smaller than itemCount -1');
+                  index >= 0 && index <= itemCount - 1,
-              return SizedBox(
+                  'index must be in the range of 0 to itemCount - 1',
-                height: itemHeight,
+                );
-                child: Text('Item $index'),
+                return SizedBox(
-              );
+                  height: itemHeight,
-            },
+                  child: Text('Item $index'),
-          ),
+                );
+              },
+            );
+          },
         ),
       ),
     );
@@ -1878,11 +1880,7 @@ void main() {
       minCacheExtent: 10,
     );
 
-    var fadeTransition = tester.widget<FadeTransition>(find
+    var fadeTransition = tester.widget<FadeTransition>(fadeTransitionFinder);
-        .descendant(
-            of: find.byType(ScrollablePositionedList),
-            matching: find.byType(FadeTransition))
-        .last);
     final initialOpacity = fadeTransition.opacity;
 
     unawaited(
@@ -1891,11 +1889,7 @@ void main() {
     await tester.pump();
     await tester.pump(scrollDuration ~/ 2);
 
-    fadeTransition = tester.widget<FadeTransition>(find
+    fadeTransition = tester.widget<FadeTransition>(fadeTransitionFinder);
-        .descendant(
-            of: find.byType(ScrollablePositionedList),
-            matching: find.byType(FadeTransition))
-        .last);
     expect(fadeTransition.opacity, initialOpacity);
 
     await tester.pumpAndSettle();
@@ -1914,11 +1908,9 @@ void main() {
       minCacheExtent: itemHeight * 200,
     );
 
-    var fadeTransition = tester.widget<FadeTransition>(find
+    var fadeTransition = tester.widget<FadeTransition>(
-        .descendant(
+      fadeTransitionFinder,
-            of: find.byType(ScrollablePositionedList),
+    );
-            matching: find.byType(FadeTransition))
-        .last);
     final initialOpacity = fadeTransition.opacity;
 
     unawaited(
@@ -1927,11 +1919,7 @@ void main() {
     await tester.pump();
     await tester.pump(scrollDuration ~/ 2);
 
-    fadeTransition = tester.widget<FadeTransition>(find
+    fadeTransition = tester.widget<FadeTransition>(fadeTransitionFinder);
-        .descendant(
-            of: find.byType(ScrollablePositionedList),
-            matching: find.byType(FadeTransition))
-        .last);
     expect(fadeTransition.opacity, initialOpacity);
 
     await tester.pumpAndSettle();
@@ -1965,17 +1953,21 @@ void main() {
       MaterialApp(
         home: ValueListenableBuilder<Key>(
           valueListenable: key,
-          builder: (context, key, child) => Container(
+          builder: (context, key, child) {
-            key: key,
+            return Container(
-            child: ScrollablePositionedList.builder(
+              key: key,
-              itemCount: 200,
+              child: ScrollablePositionedList.builder(
-              itemScrollController: itemScrollController,
+                itemCount: 200,
-              itemBuilder: (context, index) => SizedBox(
+                itemScrollController: itemScrollController,
-                height: itemHeight,
+                itemBuilder: (context, index) {
-                child: Text('Item $index'),
+                  return SizedBox(
+                    height: itemHeight,
+                    child: Text('Item $index'),
+                  );
+                },
               ),
-            ),
+            );
-          ),
+          },
         ),
       ),
     );
@@ -2054,15 +2046,19 @@ void main() {
       MaterialApp(
         home: ValueListenableBuilder<Key>(
           valueListenable: key,
-          builder: (context, key, child) => ScrollablePositionedList.builder(
+          builder: (context, key, child) {
-            key: key,
+            return ScrollablePositionedList.builder(
-            itemCount: 10,
+              key: key,
-            itemScrollController: itemScrollController,
+              itemCount: 10,
-            itemBuilder: (context, index) => SizedBox(
+              itemScrollController: itemScrollController,
-              height: itemHeight,
+              itemBuilder: (context, index) {
-              child: Text('Item $index'),
+                return SizedBox(
-            ),
+                  height: itemHeight,
-          ),
+                  child: Text('Item $index'),
+                );
+              },
+            );
+          },
         ),
       ),
     );
@@ -2084,17 +2080,21 @@ void main() {
       MaterialApp(
         home: ValueListenableBuilder<Key>(
           valueListenable: key,
-          builder: (context, key, child) => Container(
+          builder: (context, key, child) {
-            key: key,
+            return Container(
-            child: ScrollablePositionedList.builder(
+              key: key,
-              itemCount: 100,
+              child: ScrollablePositionedList.builder(
-              itemScrollController: itemScrollController,
+                itemCount: 100,
-              itemBuilder: (context, index) => SizedBox(
+                itemScrollController: itemScrollController,
-                height: itemHeight,
+                itemBuilder: (context, index) {
-                child: Text('Item $index'),
+                  return SizedBox(
+                    height: itemHeight,
+                    child: Text('Item $index'),
+                  );
+                },
               ),
-            ),
+            );
-          ),
+          },
         ),
       ),
     );
@@ -2124,18 +2124,22 @@ void main() {
       MaterialApp(
         home: ValueListenableBuilder<Key>(
           valueListenable: containerKey,
-          builder: (context, key, child) => Container(
+          builder: (context, key, child) {
-            key: key,
+            return Container(
-            child: ScrollablePositionedList.builder(
+              key: key,
-              key: scrollKey,
+              child: ScrollablePositionedList.builder(
-              itemCount: 100,
+                key: scrollKey,
-              itemScrollController: itemScrollController,
+                itemCount: 100,
-              itemBuilder: (context, index) => SizedBox(
+                itemScrollController: itemScrollController,
-                height: itemHeight,
+                itemBuilder: (context, index) {
-                child: Text('Item $index'),
+                  return SizedBox(
+                    height: itemHeight,
+                    child: Text('Item $index'),
+                  );
+                },
               ),
-            ),
+            );
-          ),
+          },
         ),
       ),
     );
@@ -2166,15 +2170,18 @@ void main() {
       MaterialApp(
         home: ValueListenableBuilder<ItemScrollController>(
           valueListenable: itemScrollControllerListenable,
-          builder: (context, itemScrollController, child) =>
+          builder: (context, itemScrollController, child) {
-              ScrollablePositionedList.builder(
+            return ScrollablePositionedList.builder(
-            itemCount: 100,
+              itemCount: 100,
-            itemScrollController: itemScrollController,
+              itemScrollController: itemScrollController,
-            itemBuilder: (context, index) => SizedBox(
+              itemBuilder: (context, index) {
-              height: itemHeight,
+                return SizedBox(
-              child: Text('Item $index'),
+                  height: itemHeight,
-            ),
+                  child: Text('Item $index'),
-          ),
+                );
+              },
+            );
+          },
         ),
       ),
     );
@@ -2215,29 +2222,35 @@ void main() {
           Expanded(
             child: ValueListenableBuilder<ItemScrollController>(
               valueListenable: topItemScrollControllerListenable,
-              builder: (context, itemScrollController, child) =>
+              builder: (context, itemScrollController, child) {
-                  ScrollablePositionedList.builder(
+                return ScrollablePositionedList.builder(
-                itemCount: 100,
+                  itemCount: 100,
-                itemScrollController: itemScrollController,
+                  itemScrollController: itemScrollController,
-                itemBuilder: (context, index) => SizedBox(
+                  itemBuilder: (context, index) {
-                  height: itemHeight,
+                    return SizedBox(
-                  child: Text('Item $index'),
+                      height: itemHeight,
-                ),
+                      child: Text('Item $index'),
-              ),
+                    );
+                  },
+                );
+              },
             ),
           ),
           Expanded(
             child: ValueListenableBuilder<ItemScrollController>(
               valueListenable: bottomItemScrollControllerListenable,
-              builder: (context, itemScrollController, child) =>
+              builder: (context, itemScrollController, child) {
-                  ScrollablePositionedList.builder(
+                return ScrollablePositionedList.builder(
-                itemCount: 100,
+                  itemCount: 100,
-                itemScrollController: itemScrollController,
+                  itemScrollController: itemScrollController,
-                itemBuilder: (context, index) => SizedBox(
+                  itemBuilder: (context, index) {
-                  height: itemHeight,
+                    return SizedBox(
-                  child: Text('Item $index'),
+                      height: itemHeight,
-                ),
+                      child: Text('Item $index'),
-              ),
+                    );
+                  },
+                );
+              },
             ),
           ),
         ],

packages/stream_chat_flutter/test/scrollable_positioned_list/separated_scrollable_positioned_list_test.dart

@@ -2,10 +2,9 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-import 'dart:async';
-
 import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';
+import 'package:pedantic/pedantic.dart';
 import 'package:stream_chat_flutter/scrollable_positioned_list/scrollable_positioned_list.dart';
 import 'package:stream_chat_flutter/scrollable_positioned_list/src/scroll_view.dart';
 
@@ -497,20 +496,21 @@ void main() {
       MaterialApp(
         home: ValueListenableBuilder<int>(
           valueListenable: itemCount,
-          builder: (context, itemCount, child) =>
+          builder: (context, itemCount, child) {
-              ScrollablePositionedList.separated(
+            return ScrollablePositionedList.separated(
-            itemCount: itemCount,
+              itemCount: itemCount,
-            itemScrollController: itemScrollController,
+              itemScrollController: itemScrollController,
-            itemPositionsListener: itemPositionsListener,
+              itemPositionsListener: itemPositionsListener,
-            itemBuilder: (context, index) => SizedBox(
+              itemBuilder: (context, index) => SizedBox(
-              height: itemHeight,
+                height: itemHeight,
-              child: Text('Item $index'),
+                child: Text('Item $index'),
-            ),
+              ),
-            separatorBuilder: (context, index) => SizedBox(
+              separatorBuilder: (context, index) => SizedBox(
-              height: separatorHeight,
+                height: separatorHeight,
-              child: Text('Separator $index'),
+                child: Text('Separator $index'),
-            ),
+              ),
-          ),
+            );
+          },
         ),
       ),
     );
@@ -538,20 +538,21 @@ void main() {
       MaterialApp(
         home: ValueListenableBuilder<int>(
           valueListenable: itemCount,
-          builder: (context, itemCount, child) =>
+          builder: (context, itemCount, child) {
-              ScrollablePositionedList.separated(
+            return ScrollablePositionedList.separated(
-            itemCount: itemCount,
+              itemCount: itemCount,
-            itemScrollController: itemScrollController,
+              itemScrollController: itemScrollController,
-            itemPositionsListener: itemPositionsListener,
+              itemPositionsListener: itemPositionsListener,
-            itemBuilder: (context, index) => SizedBox(
+              itemBuilder: (context, index) => SizedBox(
-              height: itemHeight,
+                height: itemHeight,
-              child: Text('Item $index'),
+                child: Text('Item $index'),
-            ),
+              ),
-            separatorBuilder: (context, index) => SizedBox(
+              separatorBuilder: (context, index) => SizedBox(
-              height: separatorHeight,
+                height: separatorHeight,
-              child: Text('Separator $index'),
+                child: Text('Separator $index'),
-            ),
+              ),
-          ),
+            );
+          },
         ),
       ),
     );

packages/stream_chat_flutter/test/scrollable_positioned_list/seperated_horizontal_scrollable_positioned_list_test.dart

@@ -2,10 +2,9 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-import 'dart:async';
-
 import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';
+import 'package:pedantic/pedantic.dart';
 import 'package:stream_chat_flutter/scrollable_positioned_list/scrollable_positioned_list.dart';
 
 const screenHeight = 400.0;

packages/stream_chat_flutter/test/scrollable_positioned_list/shrink_wrap_position_list_test.dart

@@ -0,0 +1,477 @@
+// Copyright 2019 The Fuchsia Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'package:flutter/material.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:stream_chat_flutter/scrollable_positioned_list/scrollable_positioned_list.dart';
+import 'package:stream_chat_flutter/scrollable_positioned_list/src/item_positions_notifier.dart';
+import 'package:stream_chat_flutter/scrollable_positioned_list/src/positioned_list.dart';
+
+const screenHeight = 400.0;
+const screenWidth = 400.0;
+const itemHeight = screenHeight / 10.0;
+const defaultItemCount = 500;
+
+void main() {
+  final itemPositionsNotifier = ItemPositionsListener.create();
+
+  Future<void> setUpWidgetTest(
+    WidgetTester tester, {
+    int topItem = 0,
+    Key? key,
+    ScrollController? scrollController,
+    double anchor = 0,
+    int itemCount = defaultItemCount,
+    bool reverse = false,
+  }) async {
+    tester.binding.window.devicePixelRatioTestValue = 1.0;
+    tester.binding.window.physicalSizeTestValue =
+        const Size(screenWidth, screenHeight);
+
+    await tester.pumpWidget(
+      MaterialApp(
+        // Use flex layout to ensure that the minimum height is not limited to
+        // screenHeight.
+        home: Column(children: [
+          // Use Constrained to make max height not more than screenHeight
+          ConstrainedBox(
+            constraints: const BoxConstraints(
+                maxHeight: screenHeight, maxWidth: screenWidth),
+            child: PositionedList(
+              key: key,
+              itemCount: itemCount,
+              positionedIndex: topItem,
+              alignment: anchor,
+              controller: scrollController,
+              itemBuilder: (context, index) => SizedBox(
+                height: itemHeight,
+                child: Text('Item $index'),
+              ),
+              itemPositionsNotifier:
+                  itemPositionsNotifier as ItemPositionsNotifier,
+              shrinkWrap: true,
+              reverse: reverse,
+            ),
+          ),
+        ]),
+      ),
+    );
+  }
+
+  testWidgets('short list with shrink wrap', (WidgetTester tester) async {
+    const itemCount = 5;
+    const key = Key('short_list');
+    await setUpWidgetTest(tester, itemCount: itemCount, key: key);
+    await tester.pump();
+
+    expect(
+        tester.getBottomRight(find.text('Item 4')).dy, itemHeight * itemCount);
+    expect(find.text('Item 4'), findsOneWidget);
+    expect(find.text('Item 5'), findsNothing);
+
+    final positionList = find.byKey(key);
+    expect(tester.getBottomRight(positionList).dy, itemHeight * itemCount);
+
+    expect(
+        itemPositionsNotifier.itemPositions.value
+            .firstWhere((position) => position.index == 0)
+            .itemLeadingEdge,
+        0);
+    expect(
+        itemPositionsNotifier.itemPositions.value
+            .firstWhere((position) => position.index == 4)
+            .itemTrailingEdge,
+        1.0);
+  });
+
+  testWidgets('List positioned with 0 at top and shrink wrap',
+      (WidgetTester tester) async {
+    await setUpWidgetTest(tester);
+    await tester.pump();
+
+    expect(find.text('Item 0'), findsOneWidget);
+    expect(find.text('Item 9'), findsOneWidget);
+    expect(find.text('Item 10'), findsNothing);
+
+    expect(
+        itemPositionsNotifier.itemPositions.value
+            .firstWhere((position) => position.index == 0)
+            .itemLeadingEdge,
+        0);
+    expect(
+        itemPositionsNotifier.itemPositions.value
+            .firstWhere((position) => position.index == 9)
+            .itemTrailingEdge,
+        1);
+    expect(
+        itemPositionsNotifier.itemPositions.value
+            .firstWhere((position) => position.index == 10)
+            .itemLeadingEdge,
+        1);
+    expect(
+        itemPositionsNotifier.itemPositions.value
+            .firstWhere((position) => position.index == 10)
+            .itemTrailingEdge,
+        11 / 10);
+  });
+
+  testWidgets('List positioned with 5 at top and shrink wrap',
+      (WidgetTester tester) async {
+    await setUpWidgetTest(tester, topItem: 5);
+    await tester.pump();
+
+    expect(find.text('Item 4'), findsNothing);
+    expect(find.text('Item 5'), findsOneWidget);
+    expect(find.text('Item 14'), findsOneWidget);
+    expect(find.text('Item 15'), findsNothing);
+
+    expect(
+        itemPositionsNotifier.itemPositions.value
+            .firstWhere((position) => position.index == 4)
+            .itemLeadingEdge,
+        -1 / 10);
+    expect(
+        itemPositionsNotifier.itemPositions.value
+            .firstWhere((position) => position.index == 4)
+            .itemTrailingEdge,
+        0);
+    expect(
+        itemPositionsNotifier.itemPositions.value
+            .firstWhere((position) => position.index == 5)
+            .itemLeadingEdge,
+        0);
+    expect(
+        itemPositionsNotifier.itemPositions.value
+            .firstWhere((position) => position.index == 14)
+            .itemTrailingEdge,
+        1);
+  });
+
+  testWidgets('List positioned with 20 at bottom and shrink wrap',
+      (WidgetTester tester) async {
+    await setUpWidgetTest(tester, topItem: 20, anchor: 1);
+    await tester.pump();
+
+    expect(find.text('Item 20'), findsNothing);
+    expect(find.text('Item 19'), findsOneWidget);
+    expect(find.text('Item 10'), findsOneWidget);
+
+    expect(
+        itemPositionsNotifier.itemPositions.value
+            .firstWhere((position) => position.index == 10)
+            .itemLeadingEdge,
+        0);
+    expect(
+        itemPositionsNotifier.itemPositions.value
+            .firstWhere((position) => position.index == 19)
+            .itemLeadingEdge,
+        9 / 10);
+    expect(
+        itemPositionsNotifier.itemPositions.value
+            .firstWhere((position) => position.index == 19)
+            .itemTrailingEdge,
+        1);
+    expect(
+        itemPositionsNotifier.itemPositions.value
+            .firstWhere((position) => position.index == 20)
+            .itemLeadingEdge,
+        1);
+  });
+
+  testWidgets('List positioned with 20 at halfway and shrink wrap',
+      (WidgetTester tester) async {
+    await setUpWidgetTest(tester, topItem: 20, anchor: 0.5);
+    await tester.pump();
+
+    expect(
+        itemPositionsNotifier.itemPositions.value
+            .firstWhere((position) => position.index == 20)
+            .itemLeadingEdge,
+        0.5);
+    expect(
+        itemPositionsNotifier.itemPositions.value
+            .firstWhere((position) => position.index == 20)
+            .itemTrailingEdge,
+        0.5 + itemHeight / screenHeight);
+  });
+
+  testWidgets('List positioned with 20 half off top of screen and shrink wrap',
+      (WidgetTester tester) async {
+    await setUpWidgetTest(tester,
+        topItem: 20, anchor: -(itemHeight / screenHeight) / 2);
+    await tester.pump();
+
+    expect(
+        itemPositionsNotifier.itemPositions.value
+            .firstWhere((position) => position.index == 20)
+            .itemLeadingEdge,
+        -(itemHeight / screenHeight) / 2);
+    expect(
+        itemPositionsNotifier.itemPositions.value
+            .firstWhere((position) => position.index == 20)
+            .itemTrailingEdge,
+        (itemHeight / screenHeight) / 2);
+  });
+
+  testWidgets('List positioned with 5 at top then scroll up 2 and shrink wrap',
+      (WidgetTester tester) async {
+    await setUpWidgetTest(tester, topItem: 5);
+
+    await tester.drag(
+        find.byType(PositionedList), const Offset(0, itemHeight * 2));
+    await tester.pump();
+
+    expect(find.text('Item 2'), findsNothing);
+    expect(find.text('Item 3'), findsOneWidget);
+    expect(find.text('Item 12'), findsOneWidget);
+    expect(find.text('Item 13'), findsNothing);
+
+    expect(
+        itemPositionsNotifier.itemPositions.value
+            .firstWhere((position) => position.index == 2)
+            .itemLeadingEdge,
+        -1 / 10);
+    expect(
+        itemPositionsNotifier.itemPositions.value
+            .firstWhere((position) => position.index == 3)
+            .itemLeadingEdge,
+        0);
+    expect(
+        itemPositionsNotifier.itemPositions.value
+            .firstWhere((position) => position.index == 12)
+            .itemTrailingEdge,
+        1);
+  });
+
+  testWidgets(
+      'List positioned with 5 at top then scroll down 1/2 and shrink wrap',
+      (WidgetTester tester) async {
+    await setUpWidgetTest(tester, topItem: 5);
+
+    await tester.drag(
+        find.byType(PositionedList), const Offset(0, -1 / 2 * itemHeight));
+    await tester.pump();
+
+    expect(
+        itemPositionsNotifier.itemPositions.value
+            .firstWhere((position) => position.index == 5)
+            .itemTrailingEdge,
+        1 / 20);
+    expect(
+        itemPositionsNotifier.itemPositions.value
+            .firstWhere((position) => position.index == 14)
+            .itemLeadingEdge,
+        17 / 20);
+  });
+
+  testWidgets('List positioned with 0 at top scroll up 5 and shrink wrap',
+      (WidgetTester tester) async {
+    final scrollController = ScrollController();
+    await setUpWidgetTest(tester, scrollController: scrollController);
+    await tester.pump();
+
+    scrollController.jumpTo(itemHeight * 5);
+    await tester.pump();
+    await tester.pumpAndSettle();
+
+    expect(find.text('Item 4'), findsNothing);
+    expect(find.text('Item 5'), findsOneWidget);
+    expect(find.text('Item 14'), findsOneWidget);
+    expect(find.text('Item 15'), findsNothing);
+
+    expect(
+        itemPositionsNotifier.itemPositions.value
+            .firstWhere((position) => position.index == 5)
+            .itemLeadingEdge,
+        0);
+    expect(
+        itemPositionsNotifier.itemPositions.value
+            .firstWhere((position) => position.index == 4)
+            .itemLeadingEdge,
+        -1 / 10);
+  });
+
+  testWidgets(
+    '''List positioned with 5 at top then scroll up 2 programatically and shrink wrap''',
+    (WidgetTester tester) async {
+      final scrollController = ScrollController();
+      await setUpWidgetTest(tester,
+          topItem: 5, scrollController: scrollController);
+
+      scrollController.jumpTo(-2 * itemHeight);
+      await tester.pump();
+
+      expect(find.text('Item 2'), findsNothing);
+      expect(find.text('Item 3'), findsOneWidget);
+      expect(find.text('Item 12'), findsOneWidget);
+      expect(find.text('Item 13'), findsNothing);
+
+      expect(
+          itemPositionsNotifier.itemPositions.value
+              .firstWhere((position) => position.index == 2)
+              .itemLeadingEdge,
+          -1 / 10);
+      expect(
+          itemPositionsNotifier.itemPositions.value
+              .firstWhere((position) => position.index == 3)
+              .itemLeadingEdge,
+          0);
+      expect(
+          itemPositionsNotifier.itemPositions.value
+              .firstWhere((position) => position.index == 12)
+              .itemTrailingEdge,
+          1);
+    },
+  );
+
+  testWidgets(
+    '''List positioned with 5 at top then scroll down 20 programatically and shrink wrap''',
+    (WidgetTester tester) async {
+      final scrollController = ScrollController();
+      await setUpWidgetTest(tester,
+          topItem: 5, scrollController: scrollController);
+
+      scrollController.jumpTo(itemHeight * 20);
+      await tester.pump();
+
+      expect(
+          itemPositionsNotifier.itemPositions.value
+              .firstWhere((position) => position.index == 23)
+              .itemLeadingEdge,
+          -2 / 10);
+      expect(
+          itemPositionsNotifier.itemPositions.value
+              .firstWhere((position) => position.index == 24)
+              .itemLeadingEdge,
+          -1 / 10);
+      expect(
+          itemPositionsNotifier.itemPositions.value
+              .firstWhere((position) => position.index == 25)
+              .itemLeadingEdge,
+          0);
+      expect(
+          itemPositionsNotifier.itemPositions.value
+              .firstWhere((position) => position.index == 4)
+              .itemLeadingEdge,
+          -21 / 10);
+      expect(
+          itemPositionsNotifier.itemPositions.value
+              .firstWhere((position) => position.index == 5)
+              .itemLeadingEdge,
+          -20 / 10);
+    },
+  );
+
+  testWidgets(
+      'List positioned with 5 at top and initial scroll offset and shrink wrap',
+      (WidgetTester tester) async {
+    final scrollController =
+        ScrollController(initialScrollOffset: -2 * itemHeight);
+    await setUpWidgetTest(tester,
+        topItem: 5, scrollController: scrollController);
+
+    expect(find.text('Item 2'), findsNothing);
+    expect(find.text('Item 3'), findsOneWidget);
+    expect(find.text('Item 12'), findsOneWidget);
+    expect(find.text('Item 13'), findsNothing);
+
+    expect(
+        itemPositionsNotifier.itemPositions.value
+            .firstWhere((position) => position.index == 3)
+            .itemLeadingEdge,
+        0);
+    expect(
+        itemPositionsNotifier.itemPositions.value
+            .firstWhere((position) => position.index == 12)
+            .itemTrailingEdge,
+        1);
+  });
+
+  testWidgets('short List with reverse and shrink wrap',
+      (WidgetTester tester) async {
+    const itemCount = 5;
+    const key = Key('short_list');
+    await setUpWidgetTest(tester,
+        itemCount: itemCount, key: key, reverse: true);
+    await tester.pump();
+
+    expect(find.text('Item 4'), findsOneWidget);
+    expect(find.text('Item 5'), findsNothing);
+    expect(
+        tester.getBottomRight(find.text('Item 0')).dy, itemHeight * itemCount);
+    expect(tester.getTopLeft(find.text('Item 4')).dy, 0);
+
+    final positionList = find.byKey(key);
+    expect(tester.getBottomRight(positionList).dy, itemHeight * itemCount);
+    expect(tester.getTopLeft(positionList).dy, 0);
+
+    expect(
+        itemPositionsNotifier.itemPositions.value
+            .firstWhere((position) => position.index == 0)
+            .itemLeadingEdge,
+        0);
+    expect(
+        itemPositionsNotifier.itemPositions.value
+            .firstWhere((position) => position.index == 4)
+            .itemTrailingEdge,
+        1.0);
+  });
+
+  testWidgets('test nested positioned list', (WidgetTester tester) async {
+    const itemCount = 50;
+    const key = Key('short_list');
+    tester.binding.window.devicePixelRatioTestValue = 1.0;
+    tester.binding.window.physicalSizeTestValue =
+        const Size(screenWidth, screenHeight);
+
+    await tester.pumpWidget(
+      MaterialApp(
+        // Use flex layout to ensure that the minimum height is not limited to
+        // screenHeight.
+        home: PositionedList(
+          itemCount: 5,
+          itemBuilder: (context, index) {
+            if (index == 0) {
+              return PositionedList(
+                  key: key,
+                  itemCount: itemCount,
+                  shrinkWrap: true,
+                  itemBuilder: (context, idx) => SizedBox(
+                        height: itemHeight,
+                        child: Text('Item $idx'),
+                      ));
+            } else {
+              return SizedBox(
+                height: itemHeight,
+                child: Text('Item ${itemCount + index - 1}'),
+              );
+            }
+          },
+          itemPositionsNotifier: itemPositionsNotifier as ItemPositionsNotifier,
+        ),
+      ),
+    );
+    await tester.pump();
+
+    expect(find.text('Item 0'), findsOneWidget);
+    expect(find.text('Item 50'), findsNothing);
+    expect(tester.getTopLeft(find.text('Item 0')).dy, 0);
+    expect(tester.getBottomRight(find.text('Item 9')).dy, screenHeight);
+
+    final positionList = find.byKey(key);
+    expect(tester.getBottomRight(positionList).dy, itemHeight * itemCount);
+    expect(tester.getTopLeft(positionList).dy, 0);
+
+    expect(
+        itemPositionsNotifier.itemPositions.value
+            .firstWhere((position) => position.index == 0)
+            .itemLeadingEdge,
+        0);
+    expect(
+        itemPositionsNotifier.itemPositions.value
+            .firstWhere((position) => position.index == 0)
+            .itemTrailingEdge,
+        5.0);
+  });
+}

packages/stream_chat_flutter/test/scrollable_positioned_list/shrink_wrap_scrollable_position_list_test.dart

@@ -0,0 +1,247 @@
+// Copyright 2019 The Fuchsia Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'package:flutter/material.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:pedantic/pedantic.dart';
+import 'package:stream_chat_flutter/scrollable_positioned_list/scrollable_positioned_list.dart';
+
+const screenHeight = 400.0;
+const screenWidth = 400.0;
+const itemHeight = screenHeight / 10.0;
+const itemCount = 500;
+const scrollDuration = Duration(seconds: 1);
+
+void main() {
+  Future<void> setUpWidgetTest(
+    WidgetTester tester, {
+    ItemScrollController? itemScrollController,
+    ItemPositionsListener? itemPositionsListener,
+    EdgeInsets? padding,
+    int initialIndex = 0,
+  }) async {
+    tester.binding.window.devicePixelRatioTestValue = 1.0;
+    tester.binding.window.physicalSizeTestValue =
+        const Size(screenWidth, screenHeight);
+
+    await tester.pumpWidget(
+      MaterialApp(
+        // Use flex layout to ensure that the minimum height is not limited to
+        // screenHeight.
+        home: Column(children: [
+          // Use Constrained to make max height not more than screenHeight
+          ConstrainedBox(
+            constraints: const BoxConstraints(
+                maxHeight: screenHeight, maxWidth: screenWidth),
+            child: ScrollablePositionedList.builder(
+              itemCount: itemCount,
+              initialScrollIndex: initialIndex,
+              itemScrollController: itemScrollController,
+              itemBuilder: (context, index) => SizedBox(
+                height: itemHeight,
+                child: Text('Item $index'),
+              ),
+              itemPositionsListener: itemPositionsListener,
+              shrinkWrap: true,
+              padding: padding,
+            ),
+          ),
+        ]),
+      ),
+    );
+  }
+
+  testWidgets('List positioned with 0 at top and shrink wrap',
+      (WidgetTester tester) async {
+    final itemPositionsListener = ItemPositionsListener.create();
+    await setUpWidgetTest(tester, itemPositionsListener: itemPositionsListener);
+
+    expect(tester.getTopLeft(find.text('Item 0')).dy, 0);
+    expect(tester.getBottomRight(find.text('Item 9')).dy, screenHeight);
+    expect(find.text('Item 10'), findsNothing);
+
+    expect(
+        itemPositionsListener.itemPositions.value
+            .firstWhere((position) => position.index == 0)
+            .itemLeadingEdge,
+        0);
+    expect(
+        itemPositionsListener.itemPositions.value
+            .firstWhere((position) => position.index == 9)
+            .itemTrailingEdge,
+        1);
+  });
+
+  testWidgets('Scroll to 1 then 2 (both already on screen) with shrink wrap',
+      (WidgetTester tester) async {
+    final itemScrollController = ItemScrollController();
+    final itemPositionsListener = ItemPositionsListener.create();
+    await setUpWidgetTest(tester,
+        itemScrollController: itemScrollController,
+        itemPositionsListener: itemPositionsListener);
+
+    unawaited(
+        itemScrollController.scrollTo(index: 1, duration: scrollDuration));
+    await tester.pump();
+    await tester.pump(scrollDuration);
+    expect(find.text('Item 0'), findsNothing);
+    expect(
+        itemPositionsListener.itemPositions.value
+            .firstWhere((position) => position.index == 1)
+            .itemLeadingEdge,
+        0);
+    expect(tester.getTopLeft(find.text('Item 1')).dy, 0);
+
+    unawaited(
+        itemScrollController.scrollTo(index: 2, duration: scrollDuration));
+    await tester.pump();
+    await tester.pump(scrollDuration);
+
+    expect(find.text('Item 1'), findsNothing);
+    expect(tester.getTopLeft(find.text('Item 2')).dy, 0);
+
+    expect(
+        itemPositionsListener.itemPositions.value
+            .firstWhere((position) => position.index == 2)
+            .itemLeadingEdge,
+        0);
+    expect(
+        itemPositionsListener.itemPositions.value
+            .firstWhere((position) => position.index == 11)
+            .itemTrailingEdge,
+        1);
+  });
+
+  testWidgets(
+      'Scroll to 5 (already on screen) and then back to 0 with shrink wrap',
+      (WidgetTester tester) async {
+    final itemScrollController = ItemScrollController();
+    final itemPositionsListener = ItemPositionsListener.create();
+    await setUpWidgetTest(tester,
+        itemScrollController: itemScrollController,
+        itemPositionsListener: itemPositionsListener);
+
+    unawaited(
+        itemScrollController.scrollTo(index: 5, duration: scrollDuration));
+    await tester.pumpAndSettle();
+    unawaited(
+        itemScrollController.scrollTo(index: 0, duration: scrollDuration));
+    await tester.pumpAndSettle();
+
+    expect(find.text('Item 0'), findsOneWidget);
+    expect(find.text('Item 9'), findsOneWidget);
+    expect(find.text('Item 10'), findsNothing);
+
+    expect(
+        itemPositionsListener.itemPositions.value
+            .firstWhere((position) => position.index == 0)
+            .itemLeadingEdge,
+        0);
+    expect(
+        itemPositionsListener.itemPositions.value
+            .firstWhere((position) => position.index == 9)
+            .itemTrailingEdge,
+        1);
+  });
+
+  testWidgets('Scroll to 100 (not already on screen) with shrink wrap',
+      (WidgetTester tester) async {
+    final itemScrollController = ItemScrollController();
+    final itemPositionsListener = ItemPositionsListener.create();
+    await setUpWidgetTest(tester,
+        itemScrollController: itemScrollController,
+        itemPositionsListener: itemPositionsListener);
+
+    unawaited(
+        itemScrollController.scrollTo(index: 100, duration: scrollDuration));
+    await tester.pumpAndSettle();
+
+    expect(find.text('Item 99'), findsNothing);
+    expect(find.text('Item 100'), findsOneWidget);
+
+    expect(
+        itemPositionsListener.itemPositions.value
+            .firstWhere((position) => position.index == 100)
+            .itemLeadingEdge,
+        0);
+    expect(
+        itemPositionsListener.itemPositions.value
+            .firstWhere((position) => position.index == 109)
+            .itemTrailingEdge,
+        1);
+  });
+
+  testWidgets('Jump to 100 with shrink wrap', (WidgetTester tester) async {
+    final itemScrollController = ItemScrollController();
+    final itemPositionsListener = ItemPositionsListener.create();
+    await setUpWidgetTest(tester,
+        itemScrollController: itemScrollController,
+        itemPositionsListener: itemPositionsListener);
+
+    itemScrollController.jumpTo(index: 100);
+    await tester.pumpAndSettle();
+
+    expect(tester.getTopLeft(find.text('Item 100')).dy, 0);
+    expect(tester.getBottomRight(find.text('Item 109')).dy, screenHeight);
+
+    expect(
+        itemPositionsListener.itemPositions.value
+            .firstWhere((position) => position.index == 100)
+            .itemLeadingEdge,
+        0);
+    expect(
+        itemPositionsListener.itemPositions.value
+            .firstWhere((position) => position.index == 109)
+            .itemTrailingEdge,
+        1);
+  });
+
+  testWidgets('padding test - centered sliver at bottom with shrink wrap',
+      (WidgetTester tester) async {
+    final itemScrollController = ItemScrollController();
+    await setUpWidgetTest(
+      tester,
+      itemScrollController: itemScrollController,
+      padding: const EdgeInsets.all(10),
+    );
+
+    expect(tester.getTopLeft(find.text('Item 0')), const Offset(10, 10));
+    expect(tester.getTopLeft(find.text('Item 1')),
+        const Offset(10, itemHeight + 10));
+    expect(tester.getBottomRight(find.text('Item 1')),
+        const Offset(screenWidth - 10, 10 + itemHeight * 2));
+
+    unawaited(
+        itemScrollController.scrollTo(index: 490, duration: scrollDuration));
+    await tester.pumpAndSettle();
+
+    await tester.drag(
+        find.byType(ScrollablePositionedList), const Offset(0, -100));
+    await tester.pumpAndSettle();
+
+    expect(tester.getTopLeft(find.text('Item 499')),
+        const Offset(10, screenHeight - itemHeight - 10));
+  });
+
+  testWidgets('padding test - centered sliver not at bottom',
+      (WidgetTester tester) async {
+    final itemScrollController = ItemScrollController();
+    await setUpWidgetTest(
+      tester,
+      itemScrollController: itemScrollController,
+      initialIndex: 2,
+      padding: const EdgeInsets.all(10),
+    );
+
+    await tester.drag(
+        find.byType(ScrollablePositionedList), const Offset(0, 200));
+    await tester.pumpAndSettle();
+
+    expect(tester.getTopLeft(find.text('Item 0')), const Offset(10, 10));
+    expect(tester.getTopLeft(find.text('Item 2')),
+        const Offset(10, 10 + itemHeight * 2));
+    expect(tester.getTopLeft(find.text('Item 3')),
+        const Offset(10, 10 + itemHeight * 3));
+  });
+}