remove IScrollSnapPointsInfo implementation from ItemsControl

src/Avalonia.Controls/ItemsControl.cs

@@ -23,7 +23,7 @@ namespace Avalonia.Controls
     /// Displays a collection of items.
     /// </summary>
     [PseudoClasses(":empty", ":singleitem")]
-    public class ItemsControl : TemplatedControl, IChildIndexProvider, IScrollSnapPointsInfo
+    public class ItemsControl : TemplatedControl, IChildIndexProvider
     {
         /// <summary>
         /// The default value for the <see cref="ItemsPanel"/> property.
@@ -67,18 +67,6 @@ namespace Avalonia.Controls
         public static readonly StyledProperty<IBinding?> DisplayMemberBindingProperty =
             AvaloniaProperty.Register<ItemsControl, IBinding?>(nameof(DisplayMemberBinding));
 
-        /// <summary>
-        /// Defines the <see cref="AreHorizontalSnapPointsRegular"/> property.
-        /// </summary>
-        public static readonly StyledProperty<bool> AreHorizontalSnapPointsRegularProperty =
-            AvaloniaProperty.Register<ItemsControl, bool>(nameof(AreHorizontalSnapPointsRegular));
-
-        /// <summary>
-        /// Defines the <see cref="AreVerticalSnapPointsRegular"/> property.
-        /// </summary>
-        public static readonly StyledProperty<bool> AreVerticalSnapPointsRegularProperty =
-            AvaloniaProperty.Register<ItemsControl, bool>(nameof(AreVerticalSnapPointsRegular));
-
         /// <summary>
         /// Gets or sets the <see cref="IBinding"/> to use for binding to the display member of each item.
         /// </summary>
@@ -249,64 +237,6 @@ namespace Avalonia.Controls
         /// </remarks>
         public event EventHandler<ContainerClearingEventArgs>? ContainerClearing;
 
-        /// <inheritdoc />
-        public event EventHandler<RoutedEventArgs> HorizontalSnapPointsChanged
-        {
-            add
-            {
-                if (_itemsPresenter != null)
-                {
-                    _itemsPresenter.HorizontalSnapPointsChanged += value;
-                }
-            }
-
-            remove
-            {
-                if (_itemsPresenter != null)
-                {
-                    _itemsPresenter.HorizontalSnapPointsChanged -= value;
-                }
-            }
-        }
-
-        /// <inheritdoc />
-        public event EventHandler<RoutedEventArgs> VerticalSnapPointsChanged
-        {
-            add
-            {
-                if (_itemsPresenter != null)
-                {
-                    _itemsPresenter.VerticalSnapPointsChanged += value;
-                }
-            }
-
-            remove
-            {
-                if (_itemsPresenter != null)
-                {
-                    _itemsPresenter.VerticalSnapPointsChanged -= value;
-                }
-            }
-        }
-
-        /// <summary>
-        /// Gets or sets whether the horizontal snap points for the <see cref="ItemsControl"/> are equidistant from each other.
-        /// </summary>
-        public bool AreHorizontalSnapPointsRegular
-        {
-            get => GetValue(AreHorizontalSnapPointsRegularProperty);
-            set => SetValue(AreHorizontalSnapPointsRegularProperty, value);
-        }
-
-        /// <summary>
-        /// Gets or sets whether the vertical snap points for the <see cref="ItemsControl"/> are equidistant from each other.
-        /// </summary>
-        public bool AreVerticalSnapPointsRegular
-        {
-            get => GetValue(AreVerticalSnapPointsRegularProperty);
-            set => SetValue(AreVerticalSnapPointsRegularProperty, value);
-        }
-
         /// <summary>
         /// Gets a default recycle key that can be used when an <see cref="ItemsControl"/> supports
         /// a single container type.
@@ -896,19 +826,5 @@ namespace Avalonia.Controls
             count = ItemsView.Count;
             return true;
         }
-
-        /// <inheritdoc />
-        public IReadOnlyList<double> GetIrregularSnapPoints(Orientation orientation, SnapPointsAlignment snapPointsAlignment)
-        {
-            return _itemsPresenter?.GetIrregularSnapPoints(orientation, snapPointsAlignment) ?? new List<double>();
-        }
-
-        /// <inheritdoc />
-        public double GetRegularSnapPoints(Orientation orientation, SnapPointsAlignment snapPointsAlignment, out double offset)
-        {
-            offset = 0;
-
-            return _itemsPresenter?.GetRegularSnapPoints(orientation, snapPointsAlignment, out offset) ?? 0;
-        }
     }
 }

src/Avalonia.Controls/Presenters/ItemsPresenter.cs

@@ -11,7 +11,7 @@ namespace Avalonia.Controls.Presenters
     /// <summary>
     /// Presents items inside an <see cref="Avalonia.Controls.ItemsControl"/>.
     /// </summary>
-    public class ItemsPresenter : Control, ILogicalScrollable, IScrollSnapPointsInfo
+    public class ItemsPresenter : Control, ILogicalScrollable
     {
         /// <summary>
         /// Defines the <see cref="ItemsPanel"/> property.
@@ -21,37 +21,8 @@ namespace Avalonia.Controls.Presenters
 
         private PanelContainerGenerator? _generator;
         private ILogicalScrollable? _logicalScrollable;
-        private IScrollSnapPointsInfo? _scrollSnapPointsInfo;
         private EventHandler? _scrollInvalidated;
 
-        /// <summary>
-        /// Defines the <see cref="AreHorizontalSnapPointsRegular"/> property.
-        /// </summary>
-        public static readonly StyledProperty<bool> AreHorizontalSnapPointsRegularProperty =
-            AvaloniaProperty.Register<ItemsPresenter, bool>(nameof(AreHorizontalSnapPointsRegular));
-
-        /// <summary>
-        /// Defines the <see cref="AreVerticalSnapPointsRegular"/> property.
-        /// </summary>
-        public static readonly StyledProperty<bool> AreVerticalSnapPointsRegularProperty =
-            AvaloniaProperty.Register<ItemsPresenter, bool>(nameof(AreVerticalSnapPointsRegular));
-
-        /// <summary>
-        /// Defines the <see cref="HorizontalSnapPointsChanged"/> event.
-        /// </summary>
-        public static readonly RoutedEvent<RoutedEventArgs> HorizontalSnapPointsChangedEvent =
-            RoutedEvent.Register<ItemsPresenter, RoutedEventArgs>(
-                nameof(HorizontalSnapPointsChanged),
-                RoutingStrategies.Bubble);
-
-        /// <summary>
-        /// Defines the <see cref="VerticalSnapPointsChanged"/> event.
-        /// </summary>
-        public static readonly RoutedEvent<RoutedEventArgs> VerticalSnapPointsChangedEvent =
-            RoutedEvent.Register<ItemsPresenter, RoutedEventArgs>(
-                nameof(VerticalSnapPointsChanged),
-                RoutingStrategies.Bubble);
-
         event EventHandler? ILogicalScrollable.ScrollInvalidated
         {
             add => _scrollInvalidated += value;
@@ -107,47 +78,12 @@ namespace Avalonia.Controls.Presenters
             }
         }
 
-        /// <summary>
-        /// Occurs when the measurements for horizontal snap points change.
-        /// </summary>
-        public event EventHandler<RoutedEventArgs>? HorizontalSnapPointsChanged
-        {
-            add => AddHandler(HorizontalSnapPointsChangedEvent, value);
-            remove => RemoveHandler(HorizontalSnapPointsChangedEvent, value);
-        }
-
-        /// <summary>
-        /// Occurs when the measurements for vertical snap points change.
-        /// </summary>
-        public event EventHandler<RoutedEventArgs>? VerticalSnapPointsChanged
-        {
-            add => AddHandler(VerticalSnapPointsChangedEvent, value);
-            remove => RemoveHandler(VerticalSnapPointsChangedEvent, value);
-        }
-
         bool ILogicalScrollable.IsLogicalScrollEnabled => _logicalScrollable?.IsLogicalScrollEnabled ?? false;
         Size ILogicalScrollable.ScrollSize => _logicalScrollable?.ScrollSize ?? default;
         Size ILogicalScrollable.PageScrollSize => _logicalScrollable?.PageScrollSize ?? default;
         Size IScrollable.Extent => _logicalScrollable?.Extent ?? default;
         Size IScrollable.Viewport => _logicalScrollable?.Viewport ?? default;
 
-        /// <summary>
-        /// Gets or sets whether the horizontal snap points for the <see cref="ItemsPresenter"/> are equidistant from each other.
-        /// </summary>
-        public bool AreHorizontalSnapPointsRegular
-        {
-            get { return GetValue(AreHorizontalSnapPointsRegularProperty); }
-            set { SetValue(AreHorizontalSnapPointsRegularProperty, value); }
-        }
-
-        /// <summary>
-        /// Gets or sets whether the vertical snap points for the <see cref="ItemsPresenter"/> are equidistant from each other.
-        /// </summary>
-        public bool AreVerticalSnapPointsRegular
-        {
-            get { return GetValue(AreVerticalSnapPointsRegularProperty); }
-            set { SetValue(AreVerticalSnapPointsRegularProperty, value); }
-        }
 
         public override sealed void ApplyTemplate()
         {
@@ -167,36 +103,14 @@ namespace Avalonia.Controls.Presenters
 
                 Panel.TemplatedParent = TemplatedParent;
                 Panel.IsItemsHost = true;
-                _scrollSnapPointsInfo = Panel as IScrollSnapPointsInfo;
                 LogicalChildren.Add(Panel);
                 VisualChildren.Add(Panel);
 
-                if (_scrollSnapPointsInfo != null)
-                {
-                    _scrollSnapPointsInfo.AreVerticalSnapPointsRegular = AreVerticalSnapPointsRegular;
-                    _scrollSnapPointsInfo.AreHorizontalSnapPointsRegular = AreHorizontalSnapPointsRegular;
-                }
-
                 if (Panel is VirtualizingPanel v)
                     v.Attach(ItemsControl);
                 else
                     CreateSimplePanelGenerator();
 
-                if (Panel is IScrollSnapPointsInfo scrollSnapPointsInfo)
-                {
-                    scrollSnapPointsInfo.VerticalSnapPointsChanged += (s, e) =>
-                    {
-                        e.RoutedEvent = VerticalSnapPointsChangedEvent;
-                        RaiseEvent(e);
-                    };
-
-                    scrollSnapPointsInfo.HorizontalSnapPointsChanged += (s, e) =>
-                    {
-                        e.RoutedEvent = HorizontalSnapPointsChangedEvent;
-                        RaiseEvent(e);
-                    };
-                }
-
                 _logicalScrollable = Panel as ILogicalScrollable;
 
                 if (_logicalScrollable is not null)
@@ -240,16 +154,6 @@ namespace Avalonia.Controls.Presenters
                 ResetState();
                 InvalidateMeasure();
             }
-            else if(change.Property == AreHorizontalSnapPointsRegularProperty)
-            {
-                if (_scrollSnapPointsInfo != null)
-                    _scrollSnapPointsInfo.AreHorizontalSnapPointsRegular = AreHorizontalSnapPointsRegular;
-            }
-            else if (change.Property == AreVerticalSnapPointsRegularProperty)
-            {
-                if (_scrollSnapPointsInfo != null)
-                    _scrollSnapPointsInfo.AreVerticalSnapPointsRegular = AreVerticalSnapPointsRegular;
-            }
         }
 
         internal void Refresh()
@@ -303,27 +207,5 @@ namespace Avalonia.Controls.Presenters
         }
 
         private void OnLogicalScrollInvalidated(object? sender, EventArgs e) => _scrollInvalidated?.Invoke(this, e);
-
-        public IReadOnlyList<double> GetIrregularSnapPoints(Orientation orientation, SnapPointsAlignment snapPointsAlignment)
-        {
-            if(Panel is IScrollSnapPointsInfo scrollSnapPointsInfo)
-            {
-                return scrollSnapPointsInfo.GetIrregularSnapPoints(orientation, snapPointsAlignment);
-            }
-
-            return new List<double>();
-        }
-
-        public double GetRegularSnapPoints(Orientation orientation, SnapPointsAlignment snapPointsAlignment, out double offset)
-        {
-            if (Panel is IScrollSnapPointsInfo scrollSnapPointsInfo)
-            {
-                return scrollSnapPointsInfo.GetRegularSnapPoints(orientation, snapPointsAlignment, out offset);
-            }
-
-            offset = 0;
-
-            return 0;
-        }
     }
 }

src/Avalonia.Controls/Presenters/ScrollContentPresenter.cs

@@ -7,6 +7,7 @@ using Avalonia.Input.GestureRecognizers;
 using Avalonia.Utilities;
 using Avalonia.VisualTree;
 using System.Linq;
+using Avalonia.Interactivity;
 
 namespace Avalonia.Controls.Presenters
 {
@@ -99,6 +100,7 @@ namespace Avalonia.Controls.Presenters
         private double _horizontalSnapPointOffset;
         private CompositeDisposable? _ownerSubscriptions;
         private ScrollViewer? _owner;
+        private IScrollSnapPointsInfo? _scrollSnapPointsInfo;
 
         /// <summary>
         /// Initializes static members of the <see cref="ScrollContentPresenter"/> class.
@@ -570,7 +572,12 @@ namespace Avalonia.Controls.Presenters
 
         private void OnScrollGestureInertiaStartingEnded(object? sender, ScrollGestureInertiaStartingEventArgs e)
         {
-            if (Content is not IScrollSnapPointsInfo)
+            var scrollable = Content;
+
+            if (Content is ItemsControl itemsControl)
+                scrollable = itemsControl.Presenter?.Panel;
+
+            if (scrollable is not IScrollSnapPointsInfo)
                 return;
 
             if (_scrollGestureSnapPoints == null)
@@ -676,22 +683,6 @@ namespace Avalonia.Controls.Presenters
 
                 _owner?.SetCurrentValue(OffsetProperty, change.GetNewValue<Vector>());
             }
-            else if (change.Property == ContentProperty)
-            {
-                if (change.OldValue is IScrollSnapPointsInfo oldSnapPointsInfo)
-                {
-                    oldSnapPointsInfo.VerticalSnapPointsChanged -= ScrollSnapPointsInfoSnapPointsChanged;
-                    oldSnapPointsInfo.HorizontalSnapPointsChanged += ScrollSnapPointsInfoSnapPointsChanged;
-                }
-
-                if (Content is IScrollSnapPointsInfo scrollSnapPointsInfo)
-                {
-                    scrollSnapPointsInfo.VerticalSnapPointsChanged += ScrollSnapPointsInfoSnapPointsChanged;
-                    scrollSnapPointsInfo.HorizontalSnapPointsChanged += ScrollSnapPointsInfoSnapPointsChanged;
-                }
-
-                UpdateSnapPoints();
-            }
             else if (change.Property == ChildProperty)
             {
                 ChildChanged(change);
@@ -875,7 +866,9 @@ namespace Avalonia.Controls.Presenters
 
         private void UpdateSnapPoints()
         {
-            if (Content is IScrollSnapPointsInfo scrollSnapPointsInfo)
+            var scrollable = GetScrollSnapPointsInfo(Content);
+
+            if (scrollable is IScrollSnapPointsInfo scrollSnapPointsInfo)
             {
                 _areVerticalSnapPointsRegular = scrollSnapPointsInfo.AreVerticalSnapPointsRegular;
                 _areHorizontalSnapPointsRegular = scrollSnapPointsInfo.AreHorizontalSnapPointsRegular;
@@ -910,7 +903,9 @@ namespace Avalonia.Controls.Presenters
 
         private Vector SnapOffset(Vector offset)
         {
-            if(Content is not IScrollSnapPointsInfo)
+            var scrollable = GetScrollSnapPointsInfo(Content);
+
+            if(scrollable is null)
                 return offset;
 
             var diff = GetAlignedDiff();
@@ -1012,5 +1007,37 @@ namespace Avalonia.Controls.Presenters
             }
             return snapPoints[Math.Min(point, snapPoints.Count - 1)];
         }
+
+        private IScrollSnapPointsInfo? GetScrollSnapPointsInfo(object? content)
+        {
+            var scrollable = content;
+
+            if (Content is ItemsControl itemsControl)
+                scrollable = itemsControl.Presenter?.Panel;
+
+            if (Content is ItemsPresenter itemsPresenter)
+                scrollable = itemsPresenter.Panel;
+
+            var snapPointsInfo = scrollable as IScrollSnapPointsInfo;
+
+            if(snapPointsInfo != _scrollSnapPointsInfo)
+            {
+                if(_scrollSnapPointsInfo != null)
+                {
+                    _scrollSnapPointsInfo.VerticalSnapPointsChanged -= ScrollSnapPointsInfoSnapPointsChanged;
+                    _scrollSnapPointsInfo.HorizontalSnapPointsChanged -= ScrollSnapPointsInfoSnapPointsChanged;
+                }
+
+                _scrollSnapPointsInfo = snapPointsInfo;
+
+                if(_scrollSnapPointsInfo != null)
+                {
+                    _scrollSnapPointsInfo.VerticalSnapPointsChanged += ScrollSnapPointsInfoSnapPointsChanged;
+                    _scrollSnapPointsInfo.HorizontalSnapPointsChanged += ScrollSnapPointsInfoSnapPointsChanged;
+                }
+            }
+
+            return snapPointsInfo;
+        }
     }
 }

src/Avalonia.Themes.Fluent/Controls/ItemsControl.xaml

@@ -10,8 +10,6 @@
                 CornerRadius="{TemplateBinding CornerRadius}"
                 Padding="{TemplateBinding Padding}">
           <ItemsPresenter Name="PART_ItemsPresenter"
-                          AreVerticalSnapPointsRegular="{TemplateBinding AreVerticalSnapPointsRegular}"
-                          AreHorizontalSnapPointsRegular="{TemplateBinding AreHorizontalSnapPointsRegular}"
                           ItemsPanel="{TemplateBinding ItemsPanel}"/>
         </Border>
       </ControlTemplate>

src/Avalonia.Themes.Fluent/Controls/ListBox.xaml

@@ -40,8 +40,6 @@
                         AllowAutoHide="{TemplateBinding (ScrollViewer.AllowAutoHide)}"
                         BringIntoViewOnFocusChange="{TemplateBinding (ScrollViewer.BringIntoViewOnFocusChange)}">
             <ItemsPresenter Name="PART_ItemsPresenter"
-                            AreVerticalSnapPointsRegular="{TemplateBinding AreVerticalSnapPointsRegular}"
-                            AreHorizontalSnapPointsRegular="{TemplateBinding AreHorizontalSnapPointsRegular}"
                             ItemsPanel="{TemplateBinding ItemsPanel}"
                             Margin="{TemplateBinding Padding}"/>
           </ScrollViewer>

src/Avalonia.Themes.Simple/Controls/ItemsControl.xaml

@@ -11,8 +11,6 @@
                 BorderThickness="{TemplateBinding BorderThickness}"
                 CornerRadius="{TemplateBinding CornerRadius}">
           <ItemsPresenter Name="PART_ItemsPresenter"
-                          AreVerticalSnapPointsRegular="{TemplateBinding AreVerticalSnapPointsRegular}"
-                          AreHorizontalSnapPointsRegular="{TemplateBinding AreHorizontalSnapPointsRegular}"
                           ItemsPanel="{TemplateBinding ItemsPanel}" />
         </Border>
       </ControlTemplate>

src/Avalonia.Themes.Simple/Controls/ListBox.xaml

@@ -27,8 +27,6 @@
                         HorizontalSnapPointsType="{TemplateBinding (ScrollViewer.HorizontalSnapPointsType)}">
             <ItemsPresenter Name="PART_ItemsPresenter"
                             Margin="{TemplateBinding Padding}"
-                            AreVerticalSnapPointsRegular="{TemplateBinding AreVerticalSnapPointsRegular}"
-                            AreHorizontalSnapPointsRegular="{TemplateBinding AreHorizontalSnapPointsRegular}"
                             ItemsPanel="{TemplateBinding ItemsPanel}" />
           </ScrollViewer>
         </Border>