Virtualizing Wrap Panel WPF - free solution? [closed] - wpf

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I know this is a duplication of Is there a (good/free) VirtualizingWrapPanel available for WPF?, but the answer there does not work as I need it. Example: When I click on an item in partial view, it takes me to the item below it, or when I refresh my items to let changes take effect on the UI that I do behind the scenes, it scrolls to the top. So has anyone found a good, free (or cheap) solution since last year?
Now I know there is an option at http://www.binarymission.co.uk/Products/WPF_SL/virtualizingwrappanel_wpf_sl.htm and that works exactly how I need it, I just would really prefer not to spend a grand for 1 project. Even if it was like 200-300 I would have already bought it but $900 for that one control in one project (so far), I just can't justify.
Any suggestions would be much appreciated!
Anthony F Greco

Answer 1

Use this one: http://virtualwrappanel.codeplex.com/ .
Here's how you use it:
xmlns:local="clr-namespace:MyWinCollection"
...
<local:VirtualizingWrapPanel ..../>

Answer 2

The one on your original link just needs a bit of tweaking to be able to support ScrollIntoView on the parent ListView so that when you refresh you can put the selection/scroll position back where you want it.
Add this extra override to the class mentioned in the question (found here)
protected override void BringIndexIntoView(int index)
{
var currentVisibleMin = _offset.Y;
var currentVisibleMax = _offset.Y + _viewportSize.Height - ItemHeight;
var itemsPerLine = Math.Max((int)Math.Floor(_viewportSize.Width / ItemWidth), 1);
var verticalOffsetRequiredToPutItemAtTopRow = Math.Floor((double)index / itemsPerLine) * ItemHeight;
if (verticalOffsetRequiredToPutItemAtTopRow < currentVisibleMin) // if item is above visible area put it on the top row
SetVerticalOffset(verticalOffsetRequiredToPutItemAtTopRow);
else if (verticalOffsetRequiredToPutItemAtTopRow > currentVisibleMax) // if item is below visible area move to put it on bottom row
SetVerticalOffset(verticalOffsetRequiredToPutItemAtTopRow - _viewportSize.Height + ItemHeight);
}
While you are there the following couple of functions can be changed as below to improve performance
protected override Size MeasureOverride(Size availableSize)
{
if (_itemsControl == null)
{
return availableSize;
}
_isInMeasure = true;
_childLayouts.Clear();
var extentInfo = GetExtentInfo(availableSize, ItemHeight);
EnsureScrollOffsetIsWithinConstrains(extentInfo);
var layoutInfo = GetLayoutInfo(availableSize, ItemHeight, extentInfo);
RecycleItems(layoutInfo);
// Determine where the first item is in relation to previously realized items
var generatorStartPosition = _itemsGenerator.GeneratorPositionFromIndex(layoutInfo.FirstRealizedItemIndex);
var visualIndex = 0;
var currentX = layoutInfo.FirstRealizedItemLeft;
var currentY = layoutInfo.FirstRealizedLineTop;
using (_itemsGenerator.StartAt(generatorStartPosition, GeneratorDirection.Forward, true))
{
for (var itemIndex = layoutInfo.FirstRealizedItemIndex; itemIndex <= layoutInfo.LastRealizedItemIndex; itemIndex++, visualIndex++)
{
bool newlyRealized;
var child = (UIElement)_itemsGenerator.GenerateNext(out newlyRealized);
SetVirtualItemIndex(child, itemIndex);
if (newlyRealized)
{
InsertInternalChild(visualIndex, child);
}
else
{
// check if item needs to be moved into a new position in the Children collection
if (visualIndex < Children.Count)
{
if (Children[visualIndex] != child)
{
var childCurrentIndex = Children.IndexOf(child);
if (childCurrentIndex >= 0)
{
RemoveInternalChildRange(childCurrentIndex, 1);
Debug.WriteLine("Moving child from {0} to {1}", childCurrentIndex, visualIndex);
}
else
Debug.WriteLine("Inserting child {0}", visualIndex);
InsertInternalChild(visualIndex, child);
}
}
else
{
// we know that the child can't already be in the children collection
// because we've been inserting children in correct visualIndex order,
// and this child has a visualIndex greater than the Children.Count
AddInternalChild(child);
Debug.WriteLine("Adding child at {0}", Children.Count-1);
}
}
// only prepare the item once it has been added to the visual tree
_itemsGenerator.PrepareItemContainer(child);
if (newlyRealized)
child.Measure(new Size(ItemWidth, ItemHeight));
_childLayouts.Add(child, new Rect(currentX, currentY, ItemWidth, ItemHeight));
if (currentX + ItemWidth * 2 >= availableSize.Width)
{
// wrap to a new line
currentY += ItemHeight;
currentX = 0;
}
else
{
currentX += ItemWidth;
}
}
}
RemoveRedundantChildren();
UpdateScrollInfo(availableSize, extentInfo);
var desiredSize = new Size(double.IsInfinity(availableSize.Width) ? 0 : availableSize.Width,
double.IsInfinity(availableSize.Height) ? 0 : availableSize.Height);
_isInMeasure = false;
return desiredSize;
}
class RemoveRange
{
public int Start;
public int Length;
}
private void RecycleItems(ItemLayoutInfo layoutInfo)
{
Queue<RemoveRange> ranges = null;
int idx = 0;
RemoveRange nextRange = null;
foreach (UIElement child in Children)
{
var virtualItemIndex = GetVirtualItemIndex(child);
if (virtualItemIndex < layoutInfo.FirstRealizedItemIndex || virtualItemIndex > layoutInfo.LastRealizedItemIndex)
{
var generatorPosition = _itemsGenerator.GeneratorPositionFromIndex(virtualItemIndex);
if (generatorPosition.Index >= 0)
{
_itemsGenerator.Recycle(generatorPosition, 1);
}
if (nextRange == null)
nextRange = new RemoveRange() { Start = idx, Length = 1 };
else
nextRange.Length++;
}
else if (nextRange!= null)
{
if (ranges== null)
ranges = new Queue<RemoveRange>();
ranges.Enqueue(nextRange);
nextRange = null;
}
SetVirtualItemIndex(child, -1);
idx++;
}
if (nextRange != null)
{
if (ranges == null)
ranges = new Queue<RemoveRange>();
ranges.Enqueue(nextRange);
}
int removed = 0;
if (ranges != null)
{
foreach (var range in ranges)
{
RemoveInternalChildRange(range.Start-removed, range.Length);
removed +=range.Length;
}
}
}

Answer 3

After trying to fix the issues of the http://virtualwrappanel.codeplex.com/ control I ended up with the solution from https://stackoverflow.com/a/13560758/5887121. I also added the BringIntoView method and a DP to set the orientation.
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Controls.Primitives;
using System.Windows.Media;
namespace Wpf.Controls
{
// class from: https://github.com/samueldjack/VirtualCollection/blob/master/VirtualCollection/VirtualCollection/VirtualizingWrapPanel.cs
// MakeVisible() method from: http://www.switchonthecode.com/tutorials/wpf-tutorial-implementing-iscrollinfo
public class VirtualizingWrapPanel : VirtualizingPanel, IScrollInfo
{
private const double ScrollLineAmount = 16.0;
private Size _extentSize;
private Size _viewportSize;
private Point _offset;
private ItemsControl _itemsControl;
private readonly Dictionary<UIElement, Rect> _childLayouts = new Dictionary<UIElement, Rect>();
public static readonly DependencyProperty ItemWidthProperty =
DependencyProperty.Register("ItemWidth", typeof(double), typeof(VirtualizingWrapPanel), new PropertyMetadata(1.0, HandleItemDimensionChanged));
public static readonly DependencyProperty ItemHeightProperty =
DependencyProperty.Register("ItemHeight", typeof(double), typeof(VirtualizingWrapPanel), new PropertyMetadata(1.0, HandleItemDimensionChanged));
private static readonly DependencyProperty VirtualItemIndexProperty =
DependencyProperty.RegisterAttached("VirtualItemIndex", typeof(int), typeof(VirtualizingWrapPanel), new PropertyMetadata(-1));
private IRecyclingItemContainerGenerator _itemsGenerator;
private bool _isInMeasure;
private static int GetVirtualItemIndex(DependencyObject obj)
{
return (int)obj.GetValue(VirtualItemIndexProperty);
}
private static void SetVirtualItemIndex(DependencyObject obj, int value)
{
obj.SetValue(VirtualItemIndexProperty, value);
}
#region Orientation
/// <summary>
/// Gets and sets the orientation of the panel.
/// </summary>
/// <value>The orientation of the panel.</value>
public Orientation Orientation
{
get
{
return (Orientation)GetValue(OrientationProperty);
}
set
{
SetValue(OrientationProperty, value);
}
}
/// <summary>
/// Identifies the Orientation dependency property.
/// </summary>
/// <remarks>
/// Returns: The identifier for the Orientation dependency property.
/// </remarks>
public static readonly DependencyProperty OrientationProperty = StackPanel.OrientationProperty.AddOwner(typeof(VirtualizingWrapPanel), new FrameworkPropertyMetadata(Orientation.Horizontal));
#endregion Orientation
public double ItemHeight
{
get
{
return (double)GetValue(ItemHeightProperty);
}
set
{
SetValue(ItemHeightProperty, value);
}
}
public double ItemWidth
{
get
{
return (double)GetValue(ItemWidthProperty);
}
set
{
SetValue(ItemWidthProperty, value);
}
}
public VirtualizingWrapPanel()
{
if ( !DesignerProperties.GetIsInDesignMode(this) )
{
Dispatcher.BeginInvoke((Action)Initialize);
}
}
private void Initialize()
{
_itemsControl = ItemsControl.GetItemsOwner(this);
_itemsGenerator = (IRecyclingItemContainerGenerator)ItemContainerGenerator;
InvalidateMeasure();
}
protected override void OnItemsChanged(object sender, ItemsChangedEventArgs args)
{
base.OnItemsChanged(sender, args);
InvalidateMeasure();
}
protected override Size MeasureOverride(Size availableSize)
{
if ( _itemsControl == null )
{
return availableSize;
}
_isInMeasure = true;
_childLayouts.Clear();
var extentInfo = GetExtentInfo(availableSize);
EnsureScrollOffsetIsWithinConstrains(extentInfo);
var layoutInfo = GetLayoutInfo(availableSize, (Orientation == Orientation.Vertical) ? ItemHeight : ItemWidth, extentInfo);
RecycleItems(layoutInfo);
// Determine where the first item is in relation to previously realized items
var generatorStartPosition = _itemsGenerator.GeneratorPositionFromIndex(layoutInfo.FirstRealizedItemIndex);
var visualIndex = 0;
Double currentX = layoutInfo.FirstRealizedItemLeft;
Double currentY = layoutInfo.FirstRealizedLineTop;
using ( _itemsGenerator.StartAt(generatorStartPosition, GeneratorDirection.Forward, true) )
{
for ( var itemIndex = layoutInfo.FirstRealizedItemIndex ; itemIndex <= layoutInfo.LastRealizedItemIndex ; itemIndex++, visualIndex++ )
{
bool newlyRealized;
var child = (UIElement)_itemsGenerator.GenerateNext(out newlyRealized);
SetVirtualItemIndex(child, itemIndex);
if ( newlyRealized )
{
InsertInternalChild(visualIndex, child);
}
else
{
// check if item needs to be moved into a new position in the Children collection
if ( visualIndex < Children.Count )
{
if ( Children[visualIndex] != child )
{
var childCurrentIndex = Children.IndexOf(child);
if ( childCurrentIndex >= 0 )
{
RemoveInternalChildRange(childCurrentIndex, 1);
}
InsertInternalChild(visualIndex, child);
}
}
else
{
// we know that the child can't already be in the children collection
// because we've been inserting children in correct visualIndex order,
// and this child has a visualIndex greater than the Children.Count
AddInternalChild(child);
}
}
// only prepare the item once it has been added to the visual tree
_itemsGenerator.PrepareItemContainer(child);
child.Measure(new Size(ItemWidth, ItemHeight));
_childLayouts.Add(child, new Rect(currentX, currentY, ItemWidth, ItemHeight));
if ( Orientation == Orientation.Vertical )
{
if ( currentX + ItemWidth * 2 > availableSize.Width )
{
// wrap to a new line
currentY += ItemHeight;
currentX = 0;
}
else
{
currentX += ItemWidth;
}
}
else
{
if ( currentY + ItemHeight * 2 > availableSize.Height )
{
// wrap to a new column
currentX += ItemWidth;
currentY = 0;
}
else
{
currentY += ItemHeight;
}
}
}
}
RemoveRedundantChildren();
UpdateScrollInfo(availableSize, extentInfo);
var desiredSize = new Size(double.IsInfinity(availableSize.Width) ? 0 : availableSize.Width,
double.IsInfinity(availableSize.Height) ? 0 : availableSize.Height);
_isInMeasure = false;
return desiredSize;
}
private void EnsureScrollOffsetIsWithinConstrains(ExtentInfo extentInfo)
{
if ( Orientation == Orientation.Vertical )
{
_offset.Y = Clamp(_offset.Y, 0, extentInfo.MaxVerticalOffset);
}
else
{
_offset.X = Clamp(_offset.X, 0, extentInfo.MaxHorizontalOffset);
}
}
private void RecycleItems(ItemLayoutInfo layoutInfo)
{
foreach ( UIElement child in Children )
{
var virtualItemIndex = GetVirtualItemIndex(child);
if ( virtualItemIndex < layoutInfo.FirstRealizedItemIndex || virtualItemIndex > layoutInfo.LastRealizedItemIndex )
{
var generatorPosition = _itemsGenerator.GeneratorPositionFromIndex(virtualItemIndex);
if ( generatorPosition.Index >= 0 )
{
_itemsGenerator.Recycle(generatorPosition, 1);
}
}
SetVirtualItemIndex(child, -1);
}
}
protected override Size ArrangeOverride(Size finalSize)
{
foreach ( UIElement child in Children )
{
child.Arrange(_childLayouts[child]);
}
return finalSize;
}
private void UpdateScrollInfo(Size availableSize, ExtentInfo extentInfo)
{
_viewportSize = availableSize;
if ( Orientation == Orientation.Vertical )
{
_extentSize = new Size(availableSize.Width, extentInfo.ExtentHeight);
}
else
{
_extentSize = new Size(extentInfo.ExtentWidth, availableSize.Height);
}
InvalidateScrollInfo();
}
private void RemoveRedundantChildren()
{
// iterate backwards through the child collection because we're going to be
// removing items from it
for ( var i = Children.Count - 1 ; i >= 0 ; i-- )
{
var child = Children[i];
// if the virtual item index is -1, this indicates
// it is a recycled item that hasn't been reused this time round
if ( GetVirtualItemIndex(child) == -1 )
{
RemoveInternalChildRange(i, 1);
}
}
}
private ItemLayoutInfo GetLayoutInfo(Size availableSize, double itemHeightOrWidth, ExtentInfo extentInfo)
{
if ( _itemsControl == null )
{
return new ItemLayoutInfo();
}
// we need to ensure that there is one realized item prior to the first visible item, and one after the last visible item,
// so that keyboard navigation works properly. For example, when focus is on the first visible item, and the user
// navigates up, the ListBox selects the previous item, and the scrolls that into view - and this triggers the loading of the rest of the items
// in that row
if ( Orientation == Orientation.Vertical )
{
var firstVisibleLine = (int)Math.Floor(VerticalOffset / itemHeightOrWidth);
var firstRealizedIndex = Math.Max(extentInfo.ItemsPerLine * firstVisibleLine - 1, 0);
var firstRealizedItemLeft = firstRealizedIndex % extentInfo.ItemsPerLine * ItemWidth - HorizontalOffset;
var firstRealizedItemTop = (firstRealizedIndex / extentInfo.ItemsPerLine) * itemHeightOrWidth - VerticalOffset;
var firstCompleteLineTop = (firstVisibleLine == 0 ? firstRealizedItemTop : firstRealizedItemTop + ItemHeight);
var completeRealizedLines = (int)Math.Ceiling((availableSize.Height - firstCompleteLineTop) / itemHeightOrWidth);
var lastRealizedIndex = Math.Min(firstRealizedIndex + completeRealizedLines * extentInfo.ItemsPerLine + 2, _itemsControl.Items.Count - 1);
return new ItemLayoutInfo
{
FirstRealizedItemIndex = firstRealizedIndex,
FirstRealizedItemLeft = firstRealizedItemLeft,
FirstRealizedLineTop = firstRealizedItemTop,
LastRealizedItemIndex = lastRealizedIndex,
};
}
else
{
var firstVisibleColumn = (int)Math.Floor(HorizontalOffset / itemHeightOrWidth);
var firstRealizedIndex = Math.Max(extentInfo.ItemsPerColumn * firstVisibleColumn - 1, 0);
var firstRealizedItemTop = firstRealizedIndex % extentInfo.ItemsPerColumn * ItemHeight - VerticalOffset;
var firstRealizedItemLeft = (firstRealizedIndex / extentInfo.ItemsPerColumn) * itemHeightOrWidth - HorizontalOffset;
var firstCompleteColumnLeft = (firstVisibleColumn == 0 ? firstRealizedItemLeft : firstRealizedItemLeft + ItemWidth);
var completeRealizedColumns = (int)Math.Ceiling((availableSize.Width - firstCompleteColumnLeft) / itemHeightOrWidth);
var lastRealizedIndex = Math.Min(firstRealizedIndex + completeRealizedColumns * extentInfo.ItemsPerColumn + 2, _itemsControl.Items.Count - 1);
return new ItemLayoutInfo
{
FirstRealizedItemIndex = firstRealizedIndex,
FirstRealizedItemLeft = firstRealizedItemLeft,
FirstRealizedLineTop = firstRealizedItemTop,
LastRealizedItemIndex = lastRealizedIndex,
};
}
}
private ExtentInfo GetExtentInfo(Size viewPortSize)
{
if ( _itemsControl == null )
{
return new ExtentInfo();
}
if ( Orientation == Orientation.Vertical )
{
var itemsPerLine = Math.Max((int)Math.Floor(viewPortSize.Width / ItemWidth), 1);
var totalLines = (int)Math.Ceiling((double)_itemsControl.Items.Count / itemsPerLine);
var extentHeight = Math.Max(totalLines * ItemHeight, viewPortSize.Height);
return new ExtentInfo
{
ItemsPerLine = itemsPerLine,
TotalLines = totalLines,
ExtentHeight = extentHeight,
MaxVerticalOffset = extentHeight - viewPortSize.Height,
};
}
else
{
var itemsPerColumn = Math.Max((int)Math.Floor(viewPortSize.Height / ItemHeight), 1);
var totalColumns = (int)Math.Ceiling((double)_itemsControl.Items.Count / itemsPerColumn);
var extentWidth = Math.Max(totalColumns * ItemWidth, viewPortSize.Width);
return new ExtentInfo
{
ItemsPerColumn = itemsPerColumn,
TotalColumns = totalColumns,
ExtentWidth = extentWidth,
MaxHorizontalOffset = extentWidth - viewPortSize.Width
};
}
}
public void LineUp()
{
SetVerticalOffset(VerticalOffset - ScrollLineAmount);
}
public void LineDown()
{
SetVerticalOffset(VerticalOffset + ScrollLineAmount);
}
public void LineLeft()
{
SetHorizontalOffset(HorizontalOffset - ScrollLineAmount);
}
public void LineRight()
{
SetHorizontalOffset(HorizontalOffset + ScrollLineAmount);
}
public void PageUp()
{
SetVerticalOffset(VerticalOffset - ViewportHeight);
}
public void PageDown()
{
SetVerticalOffset(VerticalOffset + ViewportHeight);
}
public void PageLeft()
{
SetHorizontalOffset(HorizontalOffset - ItemWidth);
}
public void PageRight()
{
SetHorizontalOffset(HorizontalOffset + ItemWidth);
}
public void MouseWheelUp()
{
if ( Orientation == Orientation.Vertical )
{
SetVerticalOffset(VerticalOffset - ScrollLineAmount * SystemParameters.WheelScrollLines);
}
else
{
MouseWheelLeft();
}
}
public void MouseWheelDown()
{
if ( Orientation == Orientation.Vertical )
{
SetVerticalOffset(VerticalOffset + ScrollLineAmount * SystemParameters.WheelScrollLines);
}
else
{
MouseWheelRight();
}
}
public void MouseWheelLeft()
{
SetHorizontalOffset(HorizontalOffset - ScrollLineAmount * SystemParameters.WheelScrollLines);
}
public void MouseWheelRight()
{
SetHorizontalOffset(HorizontalOffset + ScrollLineAmount * SystemParameters.WheelScrollLines);
}
public void SetHorizontalOffset(double offset)
{
if ( _isInMeasure )
{
return;
}
offset = Clamp(offset, 0, ExtentWidth - ViewportWidth);
_offset = new Point(offset, _offset.Y);
InvalidateScrollInfo();
InvalidateMeasure();
}
public void SetVerticalOffset(double offset)
{
if ( _isInMeasure )
{
return;
}
offset = Clamp(offset, 0, ExtentHeight - ViewportHeight);
_offset = new Point(_offset.X, offset);
InvalidateScrollInfo();
InvalidateMeasure();
}
public Rect MakeVisible(Visual visual, Rect rectangle)
{
if ( rectangle.IsEmpty ||
visual == null ||
visual == this ||
!IsAncestorOf(visual) )
{
return Rect.Empty;
}
rectangle = visual.TransformToAncestor(this).TransformBounds(rectangle);
var viewRect = new Rect(HorizontalOffset, VerticalOffset, ViewportWidth, ViewportHeight);
rectangle.X += viewRect.X;
rectangle.Y += viewRect.Y;
viewRect.X = CalculateNewScrollOffset(viewRect.Left, viewRect.Right, rectangle.Left, rectangle.Right);
viewRect.Y = CalculateNewScrollOffset(viewRect.Top, viewRect.Bottom, rectangle.Top, rectangle.Bottom);
SetHorizontalOffset(viewRect.X);
SetVerticalOffset(viewRect.Y);
rectangle.Intersect(viewRect);
rectangle.X -= viewRect.X;
rectangle.Y -= viewRect.Y;
return rectangle;
}
private static double CalculateNewScrollOffset(double topView, double bottomView, double topChild, double bottomChild)
{
var offBottom = topChild < topView && bottomChild < bottomView;
var offTop = bottomChild > bottomView && topChild > topView;
var tooLarge = (bottomChild - topChild) > (bottomView - topView);
if ( !offBottom && !offTop )
return topView;
if ( (offBottom && !tooLarge) || (offTop && tooLarge) )
return topChild;
return bottomChild - (bottomView - topView);
}
public ItemLayoutInfo GetVisibleItemsRange()
{
return GetLayoutInfo(_viewportSize, (Orientation == Orientation.Vertical) ? ItemHeight : ItemWidth, GetExtentInfo(_viewportSize));
}
protected override void BringIndexIntoView(int index)
{
if ( Orientation == Orientation.Vertical )
{
var currentVisibleMin = _offset.Y;
var currentVisibleMax = _offset.Y + _viewportSize.Height - ItemHeight;
var itemsPerLine = Math.Max((int)Math.Floor(_viewportSize.Width / ItemWidth), 1);
var verticalOffsetRequiredToPutItemAtTopRow = Math.Floor((double)index / itemsPerLine) * ItemHeight;
if ( verticalOffsetRequiredToPutItemAtTopRow < currentVisibleMin ) // if item is above visible area put it on the top row
SetVerticalOffset(verticalOffsetRequiredToPutItemAtTopRow);
else if ( verticalOffsetRequiredToPutItemAtTopRow > currentVisibleMax ) // if item is below visible area move to put it on bottom row
SetVerticalOffset(verticalOffsetRequiredToPutItemAtTopRow - _viewportSize.Height + ItemHeight);
}
else
{
var currentVisibleMin = _offset.X;
var currentVisibleMax = _offset.X + _viewportSize.Width - ItemWidth;
var itemsPerColumn = Math.Max((int)Math.Floor(_viewportSize.Height / ItemHeight), 1);
var horizontalOffsetRequiredToPutItemAtLeftRow = Math.Floor((double)index / itemsPerColumn) * ItemWidth;
if ( horizontalOffsetRequiredToPutItemAtLeftRow < currentVisibleMin ) // if item is left from the visible area put it at the left most column
SetHorizontalOffset(horizontalOffsetRequiredToPutItemAtLeftRow);
else if ( horizontalOffsetRequiredToPutItemAtLeftRow > currentVisibleMax ) // if item is right from the visible area put it at the right most column
SetHorizontalOffset(horizontalOffsetRequiredToPutItemAtLeftRow - _viewportSize.Width + ItemWidth);
}
}
public bool CanVerticallyScroll
{
get;
set;
}
public bool CanHorizontallyScroll
{
get;
set;
}
public double ExtentWidth
{
get
{
return _extentSize.Width;
}
}
public double ExtentHeight
{
get
{
return _extentSize.Height;
}
}
public double ViewportWidth
{
get
{
return _viewportSize.Width;
}
}
public double ViewportHeight
{
get
{
return _viewportSize.Height;
}
}
public double HorizontalOffset
{
get
{
return _offset.X;
}
}
public double VerticalOffset
{
get
{
return _offset.Y;
}
}
public ScrollViewer ScrollOwner
{
get;
set;
}
private void InvalidateScrollInfo()
{
if ( ScrollOwner != null )
{
ScrollOwner.InvalidateScrollInfo();
}
}
private static void HandleItemDimensionChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
var wrapPanel = (d as VirtualizingWrapPanel);
if ( wrapPanel != null )
wrapPanel.InvalidateMeasure();
}
private double Clamp(double value, double min, double max)
{
return Math.Min(Math.Max(value, min), max);
}
internal class ExtentInfo
{
public int ItemsPerLine;
public Int32 ItemsPerColumn;
public int TotalLines;
public Int32 TotalColumns;
public double ExtentHeight;
public double ExtentWidth;
public double MaxVerticalOffset;
public double MaxHorizontalOffset;
}
public class ItemLayoutInfo
{
public int FirstRealizedItemIndex;
public double FirstRealizedLineTop;
public double FirstRealizedItemLeft;
public int LastRealizedItemIndex;
}
}
}

Answer 4

I was searching a week for some solution and than I had idea how to fake VirtualizingWrapPanel.
If you know width of your Items, than you can create "rows" as StackPanel and these rows render in VirtualizingStackPanel.
XAML
<ItemsControl x:Name="Thumbs" VirtualizingStackPanel.IsVirtualizing="True"
VirtualizingPanel.ScrollUnit="Pixel" ScrollViewer.CanContentScroll="True">
<ItemsControl.ItemsPanel>
<ItemsPanelTemplate>
<VirtualizingStackPanel/>
</ItemsPanelTemplate>
</ItemsControl.ItemsPanel>
<ItemsControl.ItemTemplate>
<DataTemplate>
<ItemsControl ItemsSource="{Binding}">
<ItemsControl.ItemsPanel>
<ItemsPanelTemplate>
<StackPanel Orientation="Horizontal"/>
</ItemsPanelTemplate>
</ItemsControl.ItemsPanel>
<ItemsControl.ItemTemplate>
<DataTemplate>
<Border Width="{Binding ThumbWidth}" Height="{Binding ThumbHeight}"
BorderThickness="2" BorderBrush="Black" ClipToBounds="True">
<Image Source="{Binding FilePathCacheUri}" Stretch="Fill" />
</Border>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
</DataTemplate>
</ItemsControl.ItemTemplate>
<ItemsControl.Template>
<ControlTemplate>
<ScrollViewer>
<ItemsPresenter />
</ScrollViewer>
</ControlTemplate>
</ItemsControl.Template>
</ItemsControl>
C#
public List<BaseMediaItem> MediaItems { get; set; }
public List<List<BaseMediaItem>> SplitedMediaItems { get; set; }
public MainWindow() {
InitializeComponent();
DataContext = this;
MediaItems = new List<BaseMediaItem>();
SplitedMediaItems = new List<List<BaseMediaItem>>();
}
private void MainWindow_OnLoaded(object sender, RoutedEventArgs e) {
LoadMediaItems();
SplitMediaItems();
Thumbs.ItemsSource = SplitedMediaItems;
}
public void LoadMediaItems() {
var sizes = new List<Point> {new Point(320, 180), new Point(320, 240), new Point(180, 320), new Point(240, 320)};
MediaItems.Clear();
var random = new Random();
for (var i = 0; i < 5000; i++) {
var size = sizes[random.Next(sizes.Count)];
MediaItems.Add(new BaseMediaItem($"Item {i}") {
ThumbWidth = (int)size.X,
ThumbHeight = (int)size.Y
});
}
}
public void SplitMediaItems() {
foreach (var itemsGroup in SplitedMediaItems) {
itemsGroup.Clear();
}
SplitedMediaItems.Clear();
var groupMaxWidth = Thumbs.ActualWidth;
var groupWidth = 0;
const int itemOffset = 6; //border, margin, padding, ...
var row = new List<BaseMediaItem>();
foreach (var item in MediaItems) {
if (item.ThumbWidth + itemOffset <= groupMaxWidth - groupWidth) {
row.Add(item);
groupWidth += item.ThumbWidth + itemOffset;
}
else {
SplitedMediaItems.Add(row);
row = new List<BaseMediaItem>();
row.Add(item);
groupWidth = item.ThumbWidth + itemOffset;
}
}
SplitedMediaItems.Add(row);
}