:coffin: 虚拟化环绕panel

Control/UserControls/PannelCard/RightCardControl.xaml

@@ -8,6 +8,7 @@
              xmlns:cvt="clr-namespace:GeekDesk.Converts"
               xmlns:cst="clr-namespace:GeekDesk.Constant"
              xmlns:DraggAnimatedPanel="clr-namespace:DraggAnimatedPanel"
+             xmlns:util="clr-namespace:GeekDesk.Util"
              xmlns:xf="clr-namespace:XamlFlair;assembly=XamlFlair.WPF"
              xmlns:ot="clr-namespace:GeekDesk.Control.Other" 
              xmlns:viewmodel="clr-namespace:GeekDesk.ViewModel" d:DataContext="{d:DesignInstance Type=viewmodel:AppData}"
@@ -204,7 +205,7 @@
                                                         HorizontalAlignment="Center" 
                                                         SwapCommand="{Binding SwapCommand, RelativeSource={RelativeSource AncestorType={x:Type UserControl}}}"/>-->
 
-                                        <WrapPanel Background="#00FFFFFF"
+                                        <util:VirtualizingWrapPanel 
                                                 Width="{Binding AppConfig.WindowWidth, Mode=OneWay, 
                                                 Converter={StaticResource GetWidthByWWConvert}, 
                                                 ConverterParameter={x:Static cst:WidthTypeEnum.RIGHT_CARD}}"
@@ -347,7 +348,13 @@
 
                             <ListBox.ItemsPanel>
                                 <ItemsPanelTemplate>
-                                    <VirtualizingStackPanel  Orientation="Vertical"   Background="#00FFFFFF"
+                                    <VirtualizingStackPanel  
+                                        Orientation="Vertical"   
+                                        Background="#00FFFFFF"
+                                        IsVirtualizing="True" 
+                                        IsVirtualizingWhenGrouping="True" 
+                                        ScrollUnit="Pixel" 
+                                        VirtualizationMode="Recycling"
                                            Width="{Binding RelativeSource={RelativeSource FindAncestor,AncestorType={x:Type Window}},Path=DataContext.AppConfig.WindowWidth, Mode=OneWay, 
                                                 Converter={StaticResource GetWidthByWWConvert}, 
                                                 ConverterParameter={x:Static cst:WidthTypeEnum.RIGHT_CARD}}"

GeekDesk.csproj

@@ -324,8 +324,13 @@
     <Compile Include="Util\StringUtil.cs" />
     <Compile Include="Util\SvgToGeometry.cs" />
     <Compile Include="Util\UserActivityHook.cs" />
+    <Compile Include="Util\WrpaPanel\ItemRange.cs" />
+    <Compile Include="Util\WrpaPanel\SpacingMode.cs" />
+    <Compile Include="Util\WrpaPanel\VirtualizingPanelBase.cs" />
+    <Compile Include="Util\WrpaPanel\VirtualizingWrapPanel.cs" />
     <Compile Include="Util\WindowsThumbnailProvider.cs" />
     <Compile Include="Util\WindowUtil.cs" />
+    <Compile Include="Util\WrpaPanel\ScrollDirection.cs" />
     <Compile Include="ViewModel\AppConfig.cs" />
     <Compile Include="ViewModel\AppData.cs" />
     <Compile Include="ViewModel\GradientBGParam.cs" />

MainWindow.xaml.cs

@@ -77,9 +77,12 @@ namespace GeekDesk
         /// <param name="e"></param>
         private void SearchHotKeyDown(object sender, CanExecuteRoutedEventArgs e)
         {
-            if (appData.AppConfig.SearchType == SearchType.HOT_KEY)
+            if (appData.AppConfig.SearchType == SearchType.HOT_KEY && !RunTimeStatus.SEARCH_BOX_SHOW)
             {
                 ShowSearchBox();
+            } else if (RunTimeStatus.SEARCH_BOX_SHOW)
+            {
+                HidedSearchBox();
             }
         }
 
@@ -94,7 +97,7 @@ namespace GeekDesk
             SearchBox.Focus();
 
             //执行一遍a查询
-            SearchBox_TextChanged(null, null);
+            //SearchBox_TextChanged(null, null);
         }
         /// <summary>
         /// 搜索开始

Plugins/EveryThing/EveryThingUtil.cs

@@ -132,6 +132,14 @@ namespace GeekDesk.Plugins.EveryThing
 
         public static ObservableCollection<IconInfo> NextPage()
         {
+            if (ui == 0)
+            {
+                pageCount = 40;
+            } else
+            {
+                pageCount = 20;
+            }
+
             string filePath;
             const int bufsize = 260;
             StringBuilder buf = new StringBuilder(bufsize);

Util/WrpaPanel/ItemRange.cs

@@ -0,0 +1,25 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace GeekDesk.Util.WrpaPanel
+{
+    public struct ItemRange
+    {
+        public int StartIndex { get; }
+        public int EndIndex { get; }
+
+        public ItemRange(int startIndex, int endIndex) : this()
+        {
+            StartIndex = startIndex;
+            EndIndex = endIndex;
+        }
+
+        public bool Contains(int itemIndex)
+        {
+            return itemIndex >= StartIndex && itemIndex <= EndIndex;
+        }
+    }
+}

Util/WrpaPanel/ScrollDirection.cs

@@ -0,0 +1,14 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace GeekDesk.Util.WrpaPanel
+{
+    public enum ScrollDirection
+    {
+        Vertical,
+        Horizontal
+    }
+}

Util/WrpaPanel/SpacingMode.cs

@@ -0,0 +1,28 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace GeekDesk.Util.WrpaPanel
+{
+    public enum SpacingMode
+    {
+        /// <summary>
+        /// Spacing is disabled and all items will be arranged as closely as possible.
+        /// </summary>
+        None,
+        /// <summary>
+        /// The remaining space is evenly distributed between the items on a layout row, as well as the start and end of each row.
+        /// </summary>
+        Uniform,
+        /// <summary>
+        /// The remaining space is evenly distributed between the items on a layout row, excluding the start and end of each row.
+        /// </summary>
+        BetweenItemsOnly,
+        /// <summary>
+		/// The remaining space is evenly distributed between start and end of each row.
+		/// </summary>
+        StartAndEndOnly
+    }
+}

Util/WrpaPanel/VirtualizingPanelBase.cs

@@ -0,0 +1,481 @@
+using System;
+using System.Collections.Generic;
+using System.Collections.ObjectModel;
+using System.Collections.Specialized;
+using System.Linq;
+using System.Reflection;
+using System.Text;
+using System.Threading.Tasks;
+using System.Windows.Controls.Primitives;
+using System.Windows.Controls;
+using System.Windows.Media;
+using System.Windows;
+
+namespace GeekDesk.Util.WrpaPanel
+{
+    public abstract class VirtualizingPanelBase : VirtualizingPanel, IScrollInfo
+    {
+        public static readonly DependencyProperty ScrollLineDeltaProperty = DependencyProperty.Register(nameof(ScrollLineDelta), typeof(double), typeof(VirtualizingPanelBase), new FrameworkPropertyMetadata(16.0));
+        public static readonly DependencyProperty MouseWheelDeltaProperty = DependencyProperty.Register(nameof(MouseWheelDelta), typeof(double), typeof(VirtualizingPanelBase), new FrameworkPropertyMetadata(48.0));
+        public static readonly DependencyProperty ScrollLineDeltaItemProperty = DependencyProperty.Register(nameof(ScrollLineDeltaItem), typeof(int), typeof(VirtualizingPanelBase), new FrameworkPropertyMetadata(1));
+        public static readonly DependencyProperty MouseWheelDeltaItemProperty = DependencyProperty.Register(nameof(MouseWheelDeltaItem), typeof(int), typeof(VirtualizingPanelBase), new FrameworkPropertyMetadata(3));
+
+        public ScrollViewer? ScrollOwner { get; set; }
+
+        public bool CanVerticallyScroll { get; set; }
+        public bool CanHorizontallyScroll { get; set; }
+
+        protected override bool CanHierarchicallyScrollAndVirtualizeCore => true;
+
+        /// <summary>
+        /// Scroll line delta for pixel based scrolling. The default value is 16 dp.
+        /// </summary>
+        public double ScrollLineDelta { get => (double)GetValue(ScrollLineDeltaProperty); set => SetValue(ScrollLineDeltaProperty, value); }
+
+        /// <summary>
+        /// Mouse wheel delta for pixel based scrolling. The default value is 48 dp.
+        /// </summary>        
+        public double MouseWheelDelta { get => (double)GetValue(MouseWheelDeltaProperty); set => SetValue(MouseWheelDeltaProperty, value); }
+
+        /// <summary>
+        /// Scroll line delta for item based scrolling. The default value is 1 item.
+        /// </summary>
+        public double ScrollLineDeltaItem { get => (int)GetValue(ScrollLineDeltaItemProperty); set => SetValue(ScrollLineDeltaItemProperty, value); }
+
+        /// <summary>
+        /// Mouse wheel delta for item based scrolling. The default value is 3 items.
+        /// </summary> 
+        public int MouseWheelDeltaItem { get => (int)GetValue(MouseWheelDeltaItemProperty); set => SetValue(MouseWheelDeltaItemProperty, value); }
+
+        protected ScrollUnit ScrollUnit => GetScrollUnit(ItemsControl);
+
+        /// <summary>
+        /// The direction in which the panel scrolls when user turns the mouse wheel.
+        /// </summary>
+        protected ScrollDirection MouseWheelScrollDirection { get; set; } = ScrollDirection.Vertical;
+
+
+        protected bool IsVirtualizing => GetIsVirtualizing(ItemsControl);
+
+        protected VirtualizationMode VirtualizationMode => GetVirtualizationMode(ItemsControl);
+
+        /// <summary>
+        /// Returns true if the panel is in VirtualizationMode.Recycling, otherwise false.
+        /// </summary>
+        protected bool IsRecycling => VirtualizationMode == VirtualizationMode.Recycling;
+
+        /// <summary>
+        /// The cache length before and after the viewport. 
+        /// </summary>
+        protected VirtualizationCacheLength CacheLength { get; private set; }
+
+        /// <summary>
+        /// The Unit of the cache length. Can be Pixel, Item or Page. 
+        /// When the ItemsOwner is a group item it can only be pixel or item.
+        /// </summary>
+        protected VirtualizationCacheLengthUnit CacheLengthUnit { get; private set; }
+
+
+        /// <summary>
+        /// The ItemsControl (e.g. ListView).
+        /// </summary>
+        protected ItemsControl ItemsControl => ItemsControl.GetItemsOwner(this);
+
+        /// <summary>
+        /// The ItemsControl (e.g. ListView) or if the ItemsControl is grouping a GroupItem.
+        /// </summary>
+        protected DependencyObject ItemsOwner
+        {
+            get
+            {
+                if (_itemsOwner is null)
+                {
+                    /* Use reflection to access internal method because the public 
+                     * GetItemsOwner method does always return the itmes control instead 
+                     * of the real items owner for example the group item when grouping */
+                    MethodInfo getItemsOwnerInternalMethod = typeof(ItemsControl).GetMethod(
+                        "GetItemsOwnerInternal",
+                        BindingFlags.Static | BindingFlags.NonPublic,
+                        null,
+                        new Type[] { typeof(DependencyObject) },
+                        null
+                    )!;
+                    _itemsOwner = (DependencyObject)getItemsOwnerInternalMethod.Invoke(null, new object[] { this })!;
+                }
+                return _itemsOwner;
+            }
+        }
+        private DependencyObject? _itemsOwner;
+
+        protected ReadOnlyCollection<object?> Items => ((ItemContainerGenerator)ItemContainerGenerator).Items;
+
+        protected new IRecyclingItemContainerGenerator ItemContainerGenerator
+        {
+            get
+            {
+                if (_itemContainerGenerator is null)
+                {
+                    /* Because of a bug in the framework the ItemContainerGenerator 
+                     * is null until InternalChildren accessed at least one time. */
+                    var children = InternalChildren;
+                    _itemContainerGenerator = (IRecyclingItemContainerGenerator)base.ItemContainerGenerator;
+                }
+                return _itemContainerGenerator;
+            }
+        }
+        private IRecyclingItemContainerGenerator? _itemContainerGenerator;
+
+        public double ExtentWidth => Extent.Width;
+        public double ExtentHeight => Extent.Height;
+        protected Size Extent { get; private set; } = new Size(0, 0);
+
+        public double HorizontalOffset => Offset.X;
+        public double VerticalOffset => Offset.Y;
+        protected Size Viewport { get; private set; } = new Size(0, 0);
+
+        public double ViewportWidth => Viewport.Width;
+        public double ViewportHeight => Viewport.Height;
+        protected Point Offset { get; private set; } = new Point(0, 0);
+
+        /// <summary>
+        /// The range of items that a realized in viewport or cache.
+        /// </summary>
+        protected ItemRange ItemRange { get; set; }
+
+        private Visibility previousVerticalScrollBarVisibility = Visibility.Collapsed;
+        private Visibility previousHorizontalScrollBarVisibility = Visibility.Collapsed;
+
+        protected virtual void UpdateScrollInfo(Size availableSize, Size extent)
+        {
+            bool invalidateScrollInfo = false;
+
+            if (extent != Extent)
+            {
+                Extent = extent;
+                invalidateScrollInfo = true;
+
+            }
+            if (availableSize != Viewport)
+            {
+                Viewport = availableSize;
+                invalidateScrollInfo = true;
+            }
+
+            if (ViewportHeight != 0 && VerticalOffset != 0 && VerticalOffset + ViewportHeight + 1 >= ExtentHeight)
+            {
+                Offset = new Point(Offset.X, extent.Height - availableSize.Height);
+                invalidateScrollInfo = true;
+            }
+            if (ViewportWidth != 0 && HorizontalOffset != 0 && HorizontalOffset + ViewportWidth + 1 >= ExtentWidth)
+            {
+                Offset = new Point(extent.Width - availableSize.Width, Offset.Y);
+                invalidateScrollInfo = true;
+            }
+
+            if (invalidateScrollInfo)
+            {
+                ScrollOwner?.InvalidateScrollInfo();
+            }
+        }
+
+        public virtual Rect MakeVisible(Visual visual, Rect rectangle)
+        {
+            Point pos = visual.TransformToAncestor(this).Transform(Offset);
+
+            double scrollAmountX = 0;
+            double scrollAmountY = 0;
+
+            if (pos.X < Offset.X)
+            {
+                scrollAmountX = -(Offset.X - pos.X);
+            }
+            else if ((pos.X + rectangle.Width) > (Offset.X + Viewport.Width))
+            {
+                double notVisibleX = (pos.X + rectangle.Width) - (Offset.X + Viewport.Width);
+                double maxScrollX = pos.X - Offset.X; // keep left of the visual visible
+                scrollAmountX = Math.Min(notVisibleX, maxScrollX);
+            }
+
+            if (pos.Y < Offset.Y)
+            {
+                scrollAmountY = -(Offset.Y - pos.Y);
+            }
+            else if ((pos.Y + rectangle.Height) > (Offset.Y + Viewport.Height))
+            {
+                double notVisibleY = (pos.Y + rectangle.Height) - (Offset.Y + Viewport.Height);
+                double maxScrollY = pos.Y - Offset.Y; // keep top of the visual visible
+                scrollAmountY = Math.Min(notVisibleY, maxScrollY);
+            }
+
+            SetHorizontalOffset(Offset.X + scrollAmountX);
+            SetVerticalOffset(Offset.Y + scrollAmountY);
+
+            double visibleRectWidth = Math.Min(rectangle.Width, Viewport.Width);
+            double visibleRectHeight = Math.Min(rectangle.Height, Viewport.Height);
+
+            return new Rect(scrollAmountX, scrollAmountY, visibleRectWidth, visibleRectHeight);
+        }
+
+        protected override void OnItemsChanged(object sender, ItemsChangedEventArgs args)
+        {
+            switch (args.Action)
+            {
+                case NotifyCollectionChangedAction.Remove:
+                case NotifyCollectionChangedAction.Replace:
+                    RemoveInternalChildRange(args.Position.Index, args.ItemUICount);
+                    break;
+                case NotifyCollectionChangedAction.Move:
+                    RemoveInternalChildRange(args.OldPosition.Index, args.ItemUICount);
+                    break;
+            }
+        }
+
+        protected int GetItemIndexFromChildIndex(int childIndex)
+        {
+            var generatorPosition = GetGeneratorPositionFromChildIndex(childIndex);
+            return ItemContainerGenerator.IndexFromGeneratorPosition(generatorPosition);
+        }
+
+        protected virtual GeneratorPosition GetGeneratorPositionFromChildIndex(int childIndex)
+        {
+            return new GeneratorPosition(childIndex, 0);
+        }
+
+        protected override Size MeasureOverride(Size availableSize)
+        {
+            /* Sometimes when scrolling the scrollbar gets hidden without any reason. In this case the "IsMeasureValid" 
+             * property of the ScrollOwner is false. To prevent a infinite circle the mesasure call is ignored. */
+            if (ScrollOwner != null)
+            {
+                bool verticalScrollBarGotHidden = ScrollOwner.VerticalScrollBarVisibility == ScrollBarVisibility.Auto
+                    && ScrollOwner.ComputedVerticalScrollBarVisibility != Visibility.Visible
+                    && ScrollOwner.ComputedVerticalScrollBarVisibility != previousVerticalScrollBarVisibility;
+
+                bool horizontalScrollBarGotHidden = ScrollOwner.HorizontalScrollBarVisibility == ScrollBarVisibility.Auto
+                   && ScrollOwner.ComputedHorizontalScrollBarVisibility != Visibility.Visible
+                   && ScrollOwner.ComputedHorizontalScrollBarVisibility != previousHorizontalScrollBarVisibility;
+
+                previousVerticalScrollBarVisibility = ScrollOwner.ComputedVerticalScrollBarVisibility;
+                previousHorizontalScrollBarVisibility = ScrollOwner.ComputedHorizontalScrollBarVisibility;
+
+                if (!ScrollOwner.IsMeasureValid && verticalScrollBarGotHidden || horizontalScrollBarGotHidden)
+                {
+                    return availableSize;
+                }
+            }
+
+            var groupItem = ItemsOwner as IHierarchicalVirtualizationAndScrollInfo;
+
+            Size extent;
+            Size desiredSize;
+
+            if (groupItem != null)
+            {
+                /* If the ItemsOwner is a group item the availableSize is ifinity. 
+                 * Therfore the vieport size provided by the group item is used. */
+                var viewportSize = groupItem.Constraints.Viewport.Size;
+                var headerSize = groupItem.HeaderDesiredSizes.PixelSize;
+                double availableWidth = Math.Max(viewportSize.Width - 5, 0); // left margin of 5 dp
+                double availableHeight = Math.Max(viewportSize.Height - headerSize.Height, 0);
+                availableSize = new Size(availableWidth, availableHeight);
+
+                extent = CalculateExtent(availableSize);
+
+                desiredSize = new Size(extent.Width, extent.Height);
+
+                Extent = extent;
+                Offset = groupItem.Constraints.Viewport.Location;
+                Viewport = groupItem.Constraints.Viewport.Size;
+                CacheLength = groupItem.Constraints.CacheLength;
+                CacheLengthUnit = groupItem.Constraints.CacheLengthUnit; // can be Item or Pixel
+            }
+            else
+            {
+                extent = CalculateExtent(availableSize);
+                double desiredWidth = Math.Min(availableSize.Width, extent.Width);
+                double desiredHeight = Math.Min(availableSize.Height, extent.Height);
+                desiredSize = new Size(desiredWidth, desiredHeight);
+
+                UpdateScrollInfo(desiredSize, extent);
+                CacheLength = GetCacheLength(ItemsOwner);
+                CacheLengthUnit = GetCacheLengthUnit(ItemsOwner); // can be Page, Item or Pixel
+            }
+
+            ItemRange = UpdateItemRange();
+
+            RealizeItems();
+            VirtualizeItems();
+
+            return desiredSize;
+        }
+
+        /// <summary>
+        /// Realizes visible and cached items.
+        /// </summary>
+        protected virtual void RealizeItems()
+        {
+            var startPosition = ItemContainerGenerator.GeneratorPositionFromIndex(ItemRange.StartIndex);
+
+            int childIndex = startPosition.Offset == 0 ? startPosition.Index : startPosition.Index + 1;
+
+            using (ItemContainerGenerator.StartAt(startPosition, GeneratorDirection.Forward, true))
+            {
+                for (int i = ItemRange.StartIndex; i <= ItemRange.EndIndex; i++, childIndex++)
+                {
+                    UIElement child = (UIElement)ItemContainerGenerator.GenerateNext(out bool isNewlyRealized);
+                    if (isNewlyRealized || /*recycled*/!InternalChildren.Contains(child))
+                    {
+                        if (childIndex >= InternalChildren.Count)
+                        {
+                            AddInternalChild(child);
+                        }
+                        else
+                        {
+                            InsertInternalChild(childIndex, child);
+                        }
+                        ItemContainerGenerator.PrepareItemContainer(child);
+
+                        child.Measure(new Size(double.PositiveInfinity, double.PositiveInfinity));
+                    }
+
+                    if (child is IHierarchicalVirtualizationAndScrollInfo groupItem)
+                    {
+                        groupItem.Constraints = new HierarchicalVirtualizationConstraints(
+                            new VirtualizationCacheLength(0),
+                            VirtualizationCacheLengthUnit.Item,
+                            new Rect(0, 0, ViewportWidth, ViewportHeight));
+                        child.Measure(new Size(ViewportWidth, ViewportHeight));
+                    }
+                }
+            }
+        }
+
+        /// <summary>
+        /// Virtualizes (cleanups) no longer visible or cached items.
+        /// </summary>
+        protected virtual void VirtualizeItems()
+        {
+            for (int childIndex = InternalChildren.Count - 1; childIndex >= 0; childIndex--)
+            {
+                var generatorPosition = GetGeneratorPositionFromChildIndex(childIndex);
+
+                int itemIndex = ItemContainerGenerator.IndexFromGeneratorPosition(generatorPosition);
+
+                if (itemIndex != -1 && !ItemRange.Contains(itemIndex))
+                {
+                    if (VirtualizationMode == VirtualizationMode.Recycling)
+                    {
+                        ItemContainerGenerator.Recycle(generatorPosition, 1);
+                    }
+                    else
+                    {
+                        ItemContainerGenerator.Remove(generatorPosition, 1);
+                    }
+                    RemoveInternalChildRange(childIndex, 1);
+                }
+            }
+        }
+
+        /// <summary>
+        /// Calculates the extent that would be needed to show all items.
+        /// </summary>
+        protected abstract Size CalculateExtent(Size availableSize);
+
+        /// <summary>
+        /// Calculates the item range that is visible in the viewport or cached.
+        /// </summary>
+        protected abstract ItemRange UpdateItemRange();
+
+        public void SetVerticalOffset(double offset)
+        {
+            if (offset < 0 || Viewport.Height >= Extent.Height)
+            {
+                offset = 0;
+            }
+            else if (offset + Viewport.Height >= Extent.Height)
+            {
+                offset = Extent.Height - Viewport.Height;
+            }
+            Offset = new Point(Offset.X, offset);
+            ScrollOwner?.InvalidateScrollInfo();
+            InvalidateMeasure();
+        }
+
+        public void SetHorizontalOffset(double offset)
+        {
+            if (offset < 0 || Viewport.Width >= Extent.Width)
+            {
+                offset = 0;
+            }
+            else if (offset + Viewport.Width >= Extent.Width)
+            {
+                offset = Extent.Width - Viewport.Width;
+            }
+            Offset = new Point(offset, Offset.Y);
+            ScrollOwner?.InvalidateScrollInfo();
+            InvalidateMeasure();
+        }
+
+        protected void ScrollVertical(double amount)
+        {
+            SetVerticalOffset(VerticalOffset + amount);
+        }
+
+        protected void ScrollHorizontal(double amount)
+        {
+            SetHorizontalOffset(HorizontalOffset + amount);
+        }
+
+        public void LineUp() => ScrollVertical(ScrollUnit == ScrollUnit.Pixel ? -ScrollLineDelta : GetLineUpScrollAmount());
+        public void LineDown() => ScrollVertical(ScrollUnit == ScrollUnit.Pixel ? ScrollLineDelta : GetLineDownScrollAmount());
+        public void LineLeft() => ScrollHorizontal(ScrollUnit == ScrollUnit.Pixel ? -ScrollLineDelta : GetLineLeftScrollAmount());
+        public void LineRight() => ScrollHorizontal(ScrollUnit == ScrollUnit.Pixel ? ScrollLineDelta : GetLineRightScrollAmount());
+
+        public void MouseWheelUp()
+        {
+            if (MouseWheelScrollDirection == ScrollDirection.Vertical)
+            {
+                ScrollVertical(ScrollUnit == ScrollUnit.Pixel ? -MouseWheelDelta : GetMouseWheelUpScrollAmount());
+            }
+            else
+            {
+                MouseWheelLeft();
+            }
+        }
+
+        public void MouseWheelDown()
+        {
+            if (MouseWheelScrollDirection == ScrollDirection.Vertical)
+            {
+                ScrollVertical(ScrollUnit == ScrollUnit.Pixel ? MouseWheelDelta : GetMouseWheelDownScrollAmount());
+            }
+            else
+            {
+                MouseWheelRight();
+            }
+        }
+
+        public void MouseWheelLeft() => ScrollHorizontal(ScrollUnit == ScrollUnit.Pixel ? -MouseWheelDelta : GetMouseWheelLeftScrollAmount());
+        public void MouseWheelRight() => ScrollHorizontal(ScrollUnit == ScrollUnit.Pixel ? MouseWheelDelta : GetMouseWheelRightScrollAmount());
+
+        public void PageUp() => ScrollVertical(ScrollUnit == ScrollUnit.Pixel ? -ViewportHeight : GetPageUpScrollAmount());
+        public void PageDown() => ScrollVertical(ScrollUnit == ScrollUnit.Pixel ? ViewportHeight : GetPageDownScrollAmount());
+        public void PageLeft() => ScrollHorizontal(ScrollUnit == ScrollUnit.Pixel ? -ViewportHeight : GetPageLeftScrollAmount());
+        public void PageRight() => ScrollHorizontal(ScrollUnit == ScrollUnit.Pixel ? ViewportHeight : GetPageRightScrollAmount());
+
+        protected abstract double GetLineUpScrollAmount();
+        protected abstract double GetLineDownScrollAmount();
+        protected abstract double GetLineLeftScrollAmount();
+        protected abstract double GetLineRightScrollAmount();
+
+        protected abstract double GetMouseWheelUpScrollAmount();
+        protected abstract double GetMouseWheelDownScrollAmount();
+        protected abstract double GetMouseWheelLeftScrollAmount();
+        protected abstract double GetMouseWheelRightScrollAmount();
+
+        protected abstract double GetPageUpScrollAmount();
+        protected abstract double GetPageDownScrollAmount();
+        protected abstract double GetPageLeftScrollAmount();
+        protected abstract double GetPageRightScrollAmount();
+    }
+}

Util/WrpaPanel/VirtualizingWrapPanel.cs

@@ -0,0 +1,474 @@
+using System;
+using System.Collections.Generic;
+using System.Collections.ObjectModel;
+using System.ComponentModel;
+using System.Diagnostics;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using System.Windows.Controls.Primitives;
+using System.Windows.Controls;
+using System.Windows.Input;
+using System.Windows.Media;
+using System.Windows;
+using GeekDesk.Util.WrpaPanel;
+
+namespace GeekDesk.Util.WrpaPanel
+{
+    public class VirtualizingWrapPanel : VirtualizingPanelBase
+    {
+        #region Deprecated properties
+
+        [Obsolete("Use SpacingMode")]
+        public static readonly DependencyProperty IsSpacingEnabledProperty = DependencyProperty.Register(nameof(IsSpacingEnabled), typeof(bool), typeof(VirtualizingWrapPanel), new FrameworkPropertyMetadata(true, FrameworkPropertyMetadataOptions.AffectsMeasure));
+
+        [Obsolete("Use IsSpacingEnabled")]
+        public bool SpacingEnabled { get => IsSpacingEnabled; set => IsSpacingEnabled = value; }
+
+        /// <summary>
+        ///  Gets or sets a value that specifies whether the items are distributed evenly across the width (horizontal orientation) 
+        ///  or height (vertical orientation). The default value is true.
+        /// </summary>
+        [Obsolete("Use SpacingMode")]
+        public bool IsSpacingEnabled { get => (bool)GetValue(IsSpacingEnabledProperty); set => SetValue(IsSpacingEnabledProperty, value); }
+
+        [Obsolete("Use ItemSize")]
+        public Size ChildrenSize { get => ItemSize; set => ItemSize = value; }
+
+        #endregion
+
+        public static readonly DependencyProperty SpacingModeProperty = DependencyProperty.Register(nameof(SpacingMode), typeof(SpacingMode), typeof(VirtualizingWrapPanel), new FrameworkPropertyMetadata(SpacingMode.Uniform, FrameworkPropertyMetadataOptions.AffectsMeasure));
+
+        public static readonly DependencyProperty OrientationProperty = DependencyProperty.Register(nameof(Orientation), typeof(Orientation), typeof(VirtualizingWrapPanel), new FrameworkPropertyMetadata(Orientation.Vertical, FrameworkPropertyMetadataOptions.AffectsMeasure, (obj, args) => ((VirtualizingWrapPanel)obj).Orientation_Changed()));
+
+        public static readonly DependencyProperty ItemSizeProperty = DependencyProperty.Register(nameof(ItemSize), typeof(Size), typeof(VirtualizingWrapPanel), new FrameworkPropertyMetadata(Size.Empty, FrameworkPropertyMetadataOptions.AffectsMeasure));
+
+        public static readonly DependencyProperty StretchItemsProperty = DependencyProperty.Register(nameof(StretchItems), typeof(bool), typeof(VirtualizingWrapPanel), new FrameworkPropertyMetadata(false, FrameworkPropertyMetadataOptions.AffectsArrange));
+
+        /// <summary>
+        /// Gets or sets the spacing mode used when arranging the items. The default value is <see cref="SpacingMode.Uniform"/>.
+        /// </summary>
+        public SpacingMode SpacingMode { get => (SpacingMode)GetValue(SpacingModeProperty); set => SetValue(SpacingModeProperty, value); }
+
+        /// <summary>
+        /// Gets or sets a value that specifies the orientation in which items are arranged. The default value is <see cref="Orientation.Vertical"/>.
+        /// </summary>
+        public Orientation Orientation { get => (Orientation)GetValue(OrientationProperty); set => SetValue(OrientationProperty, value); }
+
+        /// <summary>
+        /// Gets or sets a value that specifies the size of the items. The default value is <see cref="Size.Empty"/>. 
+        /// If the value is <see cref="Size.Empty"/> the size of the items gots measured by the first realized item.
+        /// </summary>
+        public Size ItemSize { get => (Size)GetValue(ItemSizeProperty); set => SetValue(ItemSizeProperty, value); }
+
+        /// <summary>
+        /// Gets or sets a value that specifies if the items get stretched to fill up remaining space. The default value is false.
+        /// </summary>
+        /// <remarks>
+        /// The MaxWidth and MaxHeight properties of the ItemContainerStyle can be used to limit the stretching. 
+        /// In this case the use of the remaining space will be determined by the SpacingMode property. 
+        /// </remarks>
+        public bool StretchItems { get => (bool)GetValue(StretchItemsProperty); set => SetValue(StretchItemsProperty, value); }
+
+        protected Size childSize;
+
+        protected int rowCount;
+
+        protected int itemsPerRowCount;
+
+        private void Orientation_Changed()
+        {
+            MouseWheelScrollDirection = Orientation == Orientation.Vertical ? ScrollDirection.Vertical : ScrollDirection.Horizontal;
+        }
+
+        protected override Size MeasureOverride(Size availableSize)
+        {
+            UpdateChildSize(availableSize);
+            return base.MeasureOverride(availableSize);
+        }
+
+        private void UpdateChildSize(Size availableSize)
+        {
+            if (ItemsOwner is IHierarchicalVirtualizationAndScrollInfo groupItem
+                && VirtualizingPanel.GetIsVirtualizingWhenGrouping(ItemsControl))
+            {
+                if (Orientation == Orientation.Vertical)
+                {
+                    availableSize.Width = groupItem.Constraints.Viewport.Size.Width;
+                    availableSize.Width = Math.Max(availableSize.Width - (Margin.Left + Margin.Right), 0);
+                }
+                else
+                {
+                    availableSize.Height = groupItem.Constraints.Viewport.Size.Height;
+                    availableSize.Height = Math.Max(availableSize.Height - (Margin.Top + Margin.Bottom), 0);
+                }
+            }
+
+            if (ItemSize != Size.Empty)
+            {
+                childSize = ItemSize;
+            }
+            else if (InternalChildren.Count != 0)
+            {
+                childSize = InternalChildren[0].DesiredSize;
+            }
+            else
+            {
+                childSize = CalculateChildSize(availableSize);
+            }
+
+            if (double.IsInfinity(GetWidth(availableSize)))
+            {
+                itemsPerRowCount = Items.Count;
+            }
+            else
+            {
+                itemsPerRowCount = Math.Max(1, (int)Math.Floor(GetWidth(availableSize) / GetWidth(childSize)));
+            }
+
+            rowCount = (int)Math.Ceiling((double)Items.Count / itemsPerRowCount);
+        }
+
+        private Size CalculateChildSize(Size availableSize)
+        {
+            if (Items.Count == 0)
+            {
+                return new Size(0, 0);
+            }
+            var startPosition = ItemContainerGenerator.GeneratorPositionFromIndex(0);
+            using (ItemContainerGenerator.StartAt(startPosition, GeneratorDirection.Forward, true))
+            {
+                var child = (UIElement)ItemContainerGenerator.GenerateNext();
+                AddInternalChild(child);
+                ItemContainerGenerator.PrepareItemContainer(child);
+                child.Measure(new Size(double.PositiveInfinity, double.PositiveInfinity));
+                return child.DesiredSize;
+            }
+        }
+
+        protected override Size CalculateExtent(Size availableSize)
+        {
+            double extentWidth = IsSpacingEnabled && SpacingMode != SpacingMode.None && !double.IsInfinity(GetWidth(availableSize))
+                ? GetWidth(availableSize)
+                : GetWidth(childSize) * itemsPerRowCount;
+
+            if (ItemsOwner is IHierarchicalVirtualizationAndScrollInfo groupItem)
+            {
+                if (Orientation == Orientation.Vertical)
+                {
+                    extentWidth = Math.Max(extentWidth - (Margin.Left + Margin.Right), 0);
+                }
+                else
+                {
+                    extentWidth = Math.Max(extentWidth - (Margin.Top + Margin.Bottom), 0);
+                }
+            }
+
+            double extentHeight = GetHeight(childSize) * rowCount;
+            return CreateSize(extentWidth, extentHeight);
+        }
+
+        protected void CalculateSpacing(Size finalSize, out double innerSpacing, out double outerSpacing)
+        {
+            Size childSize = CalculateChildArrangeSize(finalSize);
+
+            double finalWidth = GetWidth(finalSize);
+
+            double totalItemsWidth = Math.Min(GetWidth(childSize) * itemsPerRowCount, finalWidth);
+            double unusedWidth = finalWidth - totalItemsWidth;
+
+            SpacingMode spacingMode = IsSpacingEnabled ? SpacingMode : SpacingMode.None;
+
+            switch (spacingMode)
+            {
+                case SpacingMode.Uniform:
+                    innerSpacing = outerSpacing = unusedWidth / (itemsPerRowCount + 1);
+                    break;
+
+                case SpacingMode.BetweenItemsOnly:
+                    innerSpacing = unusedWidth / Math.Max(itemsPerRowCount - 1, 1);
+                    outerSpacing = 0;
+                    break;
+
+                case SpacingMode.StartAndEndOnly:
+                    innerSpacing = 0;
+                    outerSpacing = unusedWidth / 2;
+                    break;
+
+                case SpacingMode.None:
+                default:
+                    innerSpacing = 0;
+                    outerSpacing = 0;
+                    break;
+            }
+        }
+
+        protected override Size ArrangeOverride(Size finalSize)
+        {
+            double offsetX = GetX(Offset);
+            double offsetY = GetY(Offset);
+
+            /* When the items owner is a group item offset is handled by the parent panel. */
+            if (ItemsOwner is IHierarchicalVirtualizationAndScrollInfo groupItem)
+            {
+                offsetY = 0;
+            }
+
+            Size childSize = CalculateChildArrangeSize(finalSize);
+
+            CalculateSpacing(finalSize, out double innerSpacing, out double outerSpacing);
+
+            for (int childIndex = 0; childIndex < InternalChildren.Count; childIndex++)
+            {
+                UIElement child = InternalChildren[childIndex];
+
+                int itemIndex = GetItemIndexFromChildIndex(childIndex);
+
+                int columnIndex = itemIndex % itemsPerRowCount;
+                int rowIndex = itemIndex / itemsPerRowCount;
+
+                double x = outerSpacing + columnIndex * (GetWidth(childSize) + innerSpacing);
+                double y = rowIndex * GetHeight(childSize);
+
+                if (GetHeight(finalSize) == 0.0)
+                {
+                    /* When the parent panel is grouping and a cached group item is not 
+                     * in the viewport it has no valid arrangement. That means that the 
+                     * height/width is 0. Therefore the items should not be visible so 
+                     * that they are not falsely displayed. */
+                    child.Arrange(new Rect(0, 0, 0, 0));
+                }
+                else
+                {
+                    child.Arrange(CreateRect(x - offsetX, y - offsetY, childSize.Width, childSize.Height));
+                }
+            }
+
+            return finalSize;
+        }
+
+        protected Size CalculateChildArrangeSize(Size finalSize)
+        {
+            if (StretchItems)
+            {
+                if (Orientation == Orientation.Vertical)
+                {
+                    double childMaxWidth = ReadItemContainerStyle(MaxWidthProperty, double.PositiveInfinity);
+                    double maxPossibleChildWith = finalSize.Width / itemsPerRowCount;
+                    double childWidth = Math.Min(maxPossibleChildWith, childMaxWidth);
+                    return new Size(childWidth, childSize.Height);
+                }
+                else
+                {
+                    double childMaxHeight = ReadItemContainerStyle(MaxHeightProperty, double.PositiveInfinity);
+                    double maxPossibleChildHeight = finalSize.Height / itemsPerRowCount;
+                    double childHeight = Math.Min(maxPossibleChildHeight, childMaxHeight);
+                    return new Size(childSize.Width, childHeight);
+                }
+            }
+            else
+            {
+                return childSize;
+            }
+        }
+
+        private T ReadItemContainerStyle<T>(DependencyProperty property, T fallbackValue) where T : notnull
+        {
+            var value = ItemsControl.ItemContainerStyle?.Setters.OfType<Setter>()
+                .FirstOrDefault(setter => setter.Property == property)?.Value;
+            return (T)(value ?? fallbackValue);
+        }
+
+        protected override ItemRange UpdateItemRange()
+        {
+            if (!IsVirtualizing)
+            {
+                return new ItemRange(0, Items.Count - 1);
+            }
+
+            int startIndex;
+            int endIndex;
+
+            if (ItemsOwner is IHierarchicalVirtualizationAndScrollInfo groupItem)
+            {
+                if (!VirtualizingPanel.GetIsVirtualizingWhenGrouping(ItemsControl))
+                {
+                    return new ItemRange(0, Items.Count - 1);
+                }
+
+                var offset = new Point(Offset.X, groupItem.Constraints.Viewport.Location.Y);
+
+                int offsetRowIndex;
+                double offsetInPixel;
+
+                int rowCountInViewport;
+
+                if (ScrollUnit == ScrollUnit.Item)
+                {
+                    offsetRowIndex = GetY(offset) >= 1 ? (int)GetY(offset) - 1 : 0; // ignore header
+                    offsetInPixel = offsetRowIndex * GetHeight(childSize);
+                }
+                else
+                {
+                    offsetInPixel = Math.Min(Math.Max(GetY(offset) - GetHeight(groupItem.HeaderDesiredSizes.PixelSize), 0), GetHeight(Extent));
+                    offsetRowIndex = GetRowIndex(offsetInPixel);
+                }
+
+                double viewportHeight = Math.Min(GetHeight(Viewport), Math.Max(GetHeight(Extent) - offsetInPixel, 0));
+
+                rowCountInViewport = (int)Math.Ceiling((offsetInPixel + viewportHeight) / GetHeight(childSize)) - (int)Math.Floor(offsetInPixel / GetHeight(childSize));
+
+                startIndex = offsetRowIndex * itemsPerRowCount;
+                endIndex = Math.Min(((offsetRowIndex + rowCountInViewport) * itemsPerRowCount) - 1, Items.Count - 1);
+
+                if (CacheLengthUnit == VirtualizationCacheLengthUnit.Pixel)
+                {
+                    double cacheBeforeInPixel = Math.Min(CacheLength.CacheBeforeViewport, offsetInPixel);
+                    double cacheAfterInPixel = Math.Min(CacheLength.CacheAfterViewport, GetHeight(Extent) - viewportHeight - offsetInPixel);
+                    int rowCountInCacheBefore = (int)(cacheBeforeInPixel / GetHeight(childSize));
+                    int rowCountInCacheAfter = ((int)Math.Ceiling((offsetInPixel + viewportHeight + cacheAfterInPixel) / GetHeight(childSize))) - (int)Math.Ceiling((offsetInPixel + viewportHeight) / GetHeight(childSize));
+                    startIndex = Math.Max(startIndex - rowCountInCacheBefore * itemsPerRowCount, 0);
+                    endIndex = Math.Min(endIndex + rowCountInCacheAfter * itemsPerRowCount, Items.Count - 1);
+                }
+                else if (CacheLengthUnit == VirtualizationCacheLengthUnit.Item)
+                {
+                    startIndex = Math.Max(startIndex - (int)CacheLength.CacheBeforeViewport, 0);
+                    endIndex = Math.Min(endIndex + (int)CacheLength.CacheAfterViewport, Items.Count - 1);
+                }
+            }
+            else
+            {
+                double viewportSartPos = GetY(Offset);
+                double viewportEndPos = GetY(Offset) + GetHeight(Viewport);
+
+                if (CacheLengthUnit == VirtualizationCacheLengthUnit.Pixel)
+                {
+                    viewportSartPos = Math.Max(viewportSartPos - CacheLength.CacheBeforeViewport, 0);
+                    viewportEndPos = Math.Min(viewportEndPos + CacheLength.CacheAfterViewport, GetHeight(Extent));
+                }
+
+                int startRowIndex = GetRowIndex(viewportSartPos);
+                startIndex = startRowIndex * itemsPerRowCount;
+
+                int endRowIndex = GetRowIndex(viewportEndPos);
+                endIndex = Math.Min(endRowIndex * itemsPerRowCount + (itemsPerRowCount - 1), Items.Count - 1);
+
+                if (CacheLengthUnit == VirtualizationCacheLengthUnit.Page)
+                {
+                    int itemsPerPage = endIndex - startIndex + 1;
+                    startIndex = Math.Max(startIndex - (int)CacheLength.CacheBeforeViewport * itemsPerPage, 0);
+                    endIndex = Math.Min(endIndex + (int)CacheLength.CacheAfterViewport * itemsPerPage, Items.Count - 1);
+                }
+                else if (CacheLengthUnit == VirtualizationCacheLengthUnit.Item)
+                {
+                    startIndex = Math.Max(startIndex - (int)CacheLength.CacheBeforeViewport, 0);
+                    endIndex = Math.Min(endIndex + (int)CacheLength.CacheAfterViewport, Items.Count - 1);
+                }
+            }
+
+            return new ItemRange(startIndex, endIndex);
+        }
+
+        private int GetRowIndex(double location)
+        {
+            int calculatedRowIndex = (int)Math.Floor(location / GetHeight(childSize));
+            int maxRowIndex = (int)Math.Ceiling((double)Items.Count / (double)itemsPerRowCount);
+            return Math.Max(Math.Min(calculatedRowIndex, maxRowIndex), 0);
+        }
+
+        protected override void BringIndexIntoView(int index)
+        {
+            if (index < 0 || index >= Items.Count)
+            {
+                throw new ArgumentOutOfRangeException(nameof(index), $"The argument {nameof(index)} must be >= 0 and < the number of items.");
+            }
+
+            if (itemsPerRowCount == 0)
+            {
+                throw new InvalidOperationException();
+            }
+
+            var offset = (index / itemsPerRowCount) * GetHeight(childSize);
+
+            if (Orientation == Orientation.Horizontal)
+            {
+                SetHorizontalOffset(offset);
+            }
+            else
+            {
+                SetVerticalOffset(offset);
+            }
+        }
+
+        protected override double GetLineUpScrollAmount()
+        {
+            return -Math.Min(childSize.Height * ScrollLineDeltaItem, Viewport.Height);
+        }
+
+        protected override double GetLineDownScrollAmount()
+        {
+            return Math.Min(childSize.Height * ScrollLineDeltaItem, Viewport.Height);
+        }
+
+        protected override double GetLineLeftScrollAmount()
+        {
+            return -Math.Min(childSize.Width * ScrollLineDeltaItem, Viewport.Width);
+        }
+
+        protected override double GetLineRightScrollAmount()
+        {
+            return Math.Min(childSize.Width * ScrollLineDeltaItem, Viewport.Width);
+        }
+
+        protected override double GetMouseWheelUpScrollAmount()
+        {
+            return -Math.Min(childSize.Height * MouseWheelDeltaItem, Viewport.Height);
+        }
+
+        protected override double GetMouseWheelDownScrollAmount()
+        {
+            return Math.Min(childSize.Height * MouseWheelDeltaItem, Viewport.Height);
+        }
+
+        protected override double GetMouseWheelLeftScrollAmount()
+        {
+            return -Math.Min(childSize.Width * MouseWheelDeltaItem, Viewport.Width);
+        }
+
+        protected override double GetMouseWheelRightScrollAmount()
+        {
+            return Math.Min(childSize.Width * MouseWheelDeltaItem, Viewport.Width);
+        }
+
+        protected override double GetPageUpScrollAmount()
+        {
+            return -Viewport.Height;
+        }
+
+        protected override double GetPageDownScrollAmount()
+        {
+            return Viewport.Height;
+        }
+
+        protected override double GetPageLeftScrollAmount()
+        {
+            return -Viewport.Width;
+        }
+
+        protected override double GetPageRightScrollAmount()
+        {
+            return Viewport.Width;
+        }
+
+        /* orientation aware helper methods */
+
+        protected double GetX(Point point) => Orientation == Orientation.Vertical ? point.X : point.Y;
+        protected double GetY(Point point) => Orientation == Orientation.Vertical ? point.Y : point.X;
+
+        protected double GetWidth(Size size) => Orientation == Orientation.Vertical ? size.Width : size.Height;
+        protected double GetHeight(Size size) => Orientation == Orientation.Vertical ? size.Height : size.Width;
+
+        protected Size CreateSize(double width, double height) => Orientation == Orientation.Vertical ? new Size(width, height) : new Size(height, width);
+        protected Rect CreateRect(double x, double y, double width, double height) => Orientation == Orientation.Vertical ? new Rect(x, y, width, height) : new Rect(y, x, width, height);
+    }
+}