diff --git a/samples/ControlCatalog/Pages/ListBoxPage.xaml b/samples/ControlCatalog/Pages/ListBoxPage.xaml
index 7694845009..e3a706bfed 100644
--- a/samples/ControlCatalog/Pages/ListBoxPage.xaml
+++ b/samples/ControlCatalog/Pages/ListBoxPage.xaml
@@ -20,6 +20,9 @@
Hosts a collection of ListBoxItem.
diff --git a/src/Avalonia.Controls/VirtualizingStackPanel.cs b/src/Avalonia.Controls/VirtualizingStackPanel.cs
index adeebf97d9..e883bb533b 100644
--- a/src/Avalonia.Controls/VirtualizingStackPanel.cs
+++ b/src/Avalonia.Controls/VirtualizingStackPanel.cs
@@ -8,6 +8,7 @@ using Avalonia.Controls.Utils;
using Avalonia.Input;
using Avalonia.Interactivity;
using Avalonia.Layout;
+using Avalonia.Reactive;
using Avalonia.Utilities;
using Avalonia.VisualTree;
@@ -51,6 +52,12 @@ namespace Avalonia.Controls
RoutedEvent.Register(
nameof(VerticalSnapPointsChanged),
RoutingStrategies.Bubble);
+ ///
+ /// Defines the
+ public static readonly StyledProperty CacheLengthProperty =
+ AvaloniaProperty.Register(nameof(CacheLength), 0.0,
+ validate: v => v is >= 0 and <= 2);
private static readonly AttachedProperty RecycleKeyProperty =
AvaloniaProperty.RegisterAttached("RecycleKey");
@@ -73,12 +80,24 @@ namespace Avalonia.Controls
private int _focusedIndex = -1;
private Control? _realizingElement;
private int _realizingIndex = -1;
+ private double _bufferFactor;
+
+ private bool _hasReachedStart = false;
+ private bool _hasReachedEnd = false;
+ private Rect _extendedViewport;
+
+ static VirtualizingStackPanel()
+ {
+ CacheLengthProperty.Changed.AddClassHandler((x, e) => x.OnCacheLengthChanged(e));
+ }
public VirtualizingStackPanel()
{
_recycleElement = RecycleElement;
_recycleElementOnItemRemoved = RecycleElementOnItemRemoved;
_updateElementIndex = UpdateElementIndex;
+
+ _bufferFactor = Math.Max(0, CacheLength);
EffectiveViewportChanged += OnEffectiveViewportChanged;
}
@@ -131,6 +150,20 @@ namespace Avalonia.Controls
set => SetValue(AreVerticalSnapPointsRegularProperty, value);
}
+ ///
+ /// Gets or sets the CacheLength.
+ ///
+ /// The factor determines how much additional space to maintain above and below the viewport.
+ /// A value of 0.5 means half the viewport size will be buffered on each side (up-down or left-right)
+ /// This uses more memory as more UI elements are realized, but greatly reduces the number of Measure-Arrange
+ /// cycles which can cause heavy GC pressure depending on the complexity of the item layouts.
+ ///
+ public double CacheLength
+ {
+ get => GetValue(CacheLengthProperty);
+ set => SetValue(CacheLengthProperty, value);
+ }
+
///
/// Gets the index of the first realized element, or -1 if no elements are realized.
///
@@ -141,6 +174,16 @@ namespace Avalonia.Controls
///
public int LastRealizedIndex => _realizedElements?.LastIndex ?? -1;
+ ///
+ /// Returns the viewport that contains any visible elements
+ ///
+ internal Rect ViewPort => _viewport;
+
+ ///
+ /// Returns the extended viewport that contains any visible elements and the additional elements for fast scrolling (viewport * CacheLength * 2)
+ ///
+ internal Rect ExtendedViewPort => _extendedViewport;
+
protected override Size MeasureOverride(Size availableSize)
{
var items = Items;
@@ -217,8 +260,12 @@ namespace Avalonia.Controls
var rect = orientation == Orientation.Horizontal ?
new Rect(u, 0, sizeU, finalSize.Height) :
new Rect(0, u, finalSize.Width, sizeU);
+
e.Arrange(rect);
- _scrollAnchorProvider?.RegisterAnchorCandidate(e);
+
+ if (_viewport.Intersects(rect))
+ _scrollAnchorProvider?.RegisterAnchorCandidate(e);
+
u += orientation == Orientation.Horizontal ? rect.Width : rect.Height;
}
}
@@ -230,6 +277,7 @@ namespace Avalonia.Controls
var rect = orientation == Orientation.Horizontal ?
new Rect(u, 0, _focusedElement.DesiredSize.Width, finalSize.Height) :
new Rect(0, u, finalSize.Width, _focusedElement.DesiredSize.Height);
+
_focusedElement.Arrange(rect);
}
@@ -416,6 +464,7 @@ namespace Avalonia.Controls
// Create and measure the element to be brought into view. Store it in a field so that
// it can be re-used in the layout pass.
var scrollToElement = GetOrCreateElement(items, index);
+
scrollToElement.Measure(Size.Infinity);
// Get the expected position of the element and put it in place.
@@ -483,7 +532,8 @@ namespace Avalonia.Controls
{
Debug.Assert(_realizedElements is not null);
- var viewport = _viewport;
+ // Use the extended viewport for calculations
+ var viewport = _extendedViewport;
// Get the viewport in the orientation direction.
var viewportStart = orientation == Orientation.Horizontal ? viewport.X : viewport.Y;
@@ -653,7 +703,6 @@ namespace Avalonia.Controls
return index * estimatedSize;
}
-
private void RealizeElements(
IReadOnlyList items,
Size availableSize,
@@ -666,6 +715,10 @@ namespace Avalonia.Controls
var index = viewport.anchorIndex;
var horizontal = Orientation == Orientation.Horizontal;
var u = viewport.anchorU;
+
+ // Reset boundary flags
+ _hasReachedStart = false;
+ _hasReachedEnd = false;
// If the anchor element is at the beginning of, or before, the start of the viewport
// then we can recycle all elements before it.
@@ -678,8 +731,9 @@ namespace Avalonia.Controls
_realizingIndex = index;
var e = GetOrCreateElement(items, index);
_realizingElement = e;
+
e.Measure(availableSize);
-
+
var sizeU = horizontal ? e.DesiredSize.Width : e.DesiredSize.Height;
var sizeV = horizontal ? e.DesiredSize.Height : e.DesiredSize.Width;
@@ -691,7 +745,10 @@ namespace Avalonia.Controls
_realizingIndex = -1;
_realizingElement = null;
} while (u < viewport.viewportUEnd && index < items.Count);
-
+
+ // Check if we reached the end of the collection
+ _hasReachedEnd = index >= items.Count;
+
// Store the last index and end U position for the desired size calculation.
viewport.lastIndex = index - 1;
viewport.realizedEndU = u;
@@ -706,8 +763,8 @@ namespace Avalonia.Controls
while (u > viewport.viewportUStart && index >= 0)
{
var e = GetOrCreateElement(items, index);
+
e.Measure(availableSize);
-
var sizeU = horizontal ? e.DesiredSize.Width : e.DesiredSize.Height;
var sizeV = horizontal ? e.DesiredSize.Height : e.DesiredSize.Width;
u -= sizeU;
@@ -716,6 +773,9 @@ namespace Avalonia.Controls
viewport.measuredV = Math.Max(viewport.measuredV, sizeV);
--index;
}
+
+ // Check if we reached the start of the collection
+ _hasReachedStart = index < 0;
// We can now recycle elements before the first element.
_realizedElements.RecycleElementsBefore(index + 1, _recycleElement);
@@ -748,7 +808,7 @@ namespace Avalonia.Controls
{
return _realizedElements?.GetElement(index);
}
-
+
private static Control? GetRealizedElement(
int index,
ref int specialIndex,
@@ -891,22 +951,146 @@ namespace Avalonia.Controls
ItemContainerGenerator.ItemContainerIndexChanged(element, oldIndex, newIndex);
}
-
+
private void OnEffectiveViewportChanged(object? sender, EffectiveViewportChangedEventArgs e)
{
var vertical = Orientation == Orientation.Vertical;
var oldViewportStart = vertical ? _viewport.Top : _viewport.Left;
var oldViewportEnd = vertical ? _viewport.Bottom : _viewport.Right;
+ var oldExtendedViewportStart = vertical ? _extendedViewport.Top : _extendedViewport.Left;
+ var oldExtendedViewportEnd = vertical ? _extendedViewport.Bottom : _extendedViewport.Right;
+ // Update current viewport
_viewport = e.EffectiveViewport.Intersect(new(Bounds.Size));
_isWaitingForViewportUpdate = false;
+ // Calculate buffer sizes based on viewport dimensions
+ var viewportSize = vertical ? _viewport.Height : _viewport.Width;
+ var bufferSize = viewportSize * _bufferFactor;
+
+ // Calculate extended viewport with relative buffers
+ var extendedViewportStart = vertical ?
+ Math.Max(0, _viewport.Top - bufferSize) :
+ Math.Max(0, _viewport.Left - bufferSize);
+
+ var extendedViewportEnd = vertical ?
+ Math.Min(Bounds.Height, _viewport.Bottom + bufferSize) :
+ Math.Min(Bounds.Width, _viewport.Right + bufferSize);
+
+ // special case:
+ // If we are at the start of the list, append 2 * CacheLength additional items
+ // If we are at the end of the list, prepend 2 * CacheLength additional items
+ // - this way we always maintain "2 * CacheLength * element" items.
+ if (vertical)
+ {
+ var spaceAbove = _viewport.Top - bufferSize;
+ var spaceBelow = Bounds.Height - (_viewport.Bottom + bufferSize);
+
+ if (spaceAbove < 0 && spaceBelow >= 0)
+ extendedViewportEnd = Math.Min(Bounds.Height, extendedViewportEnd + Math.Abs(spaceAbove));
+ if (spaceAbove >= 0 && spaceBelow < 0)
+ extendedViewportStart = Math.Max(0, extendedViewportStart - Math.Abs(spaceBelow));
+ }
+ else
+ {
+ var spaceLeft = _viewport.Left - bufferSize;
+ var spaceRight = Bounds.Width - (_viewport.Right + bufferSize);
+
+ if (spaceLeft < 0 && spaceRight >= 0)
+ extendedViewportEnd = Math.Min(Bounds.Width, extendedViewportEnd + Math.Abs(spaceLeft));
+ if(spaceLeft >= 0 && spaceRight < 0)
+ extendedViewportStart = Math.Max(0, extendedViewportStart - Math.Abs(spaceRight));
+ }
+
+ Rect extendedViewPort;
+ if (vertical)
+ {
+ extendedViewPort = new Rect(
+ _viewport.X,
+ extendedViewportStart,
+ _viewport.Width,
+ extendedViewportEnd - extendedViewportStart);
+ }
+ else
+ {
+ extendedViewPort = new Rect(
+ extendedViewportStart,
+ _viewport.Y,
+ extendedViewportEnd - extendedViewportStart,
+ _viewport.Height);
+ }
+
+ // Determine if we need a new measure
var newViewportStart = vertical ? _viewport.Top : _viewport.Left;
var newViewportEnd = vertical ? _viewport.Bottom : _viewport.Right;
+ var newExtendedViewportStart = vertical ? extendedViewPort.Top : extendedViewPort.Left;
+ var newExtendedViewportEnd = vertical ? extendedViewPort.Bottom : extendedViewPort.Right;
+ var needsMeasure = false;
+
+
+ // Case 1: Viewport has changed significantly
if (!MathUtilities.AreClose(oldViewportStart, newViewportStart) ||
!MathUtilities.AreClose(oldViewportEnd, newViewportEnd))
{
+ // Case 1a: The new viewport exceeds the old extended viewport
+ if (newViewportStart < oldExtendedViewportStart ||
+ newViewportEnd > oldExtendedViewportEnd)
+ {
+ needsMeasure = true;
+ }
+ // Case 1b: The extended viewport has changed significantly
+ else if (!MathUtilities.AreClose(oldExtendedViewportStart, newExtendedViewportStart) ||
+ !MathUtilities.AreClose(oldExtendedViewportEnd, newExtendedViewportEnd))
+ {
+ // Check if we're about to scroll into an area where we don't have realized elements
+ // This would be the case if we're near the edge of our current extended viewport
+ var nearingEdge = false;
+
+ if (_realizedElements != null)
+ {
+ var firstRealizedElementU = _realizedElements.StartU;
+ var lastRealizedElementU = _realizedElements.StartU;
+
+ for (var i = 0; i < _realizedElements.Count; i++)
+ {
+ lastRealizedElementU += _realizedElements.SizeU[i];
+ }
+
+ // If scrolling up/left and nearing the top/left edge of realized elements
+ if (newViewportStart < oldViewportStart &&
+ newViewportStart - newExtendedViewportStart < bufferSize)
+ {
+ // Edge case: We're at item 0 with excess measurement space.
+ // Skip re-measuring since we're at the list start and it won't change the result.
+ // This prevents redundant Measure-Arrange cycles when at list beginning.
+ nearingEdge = !_hasReachedStart;
+ }
+
+ // If scrolling down/right and nearing the bottom/right edge of realized elements
+ if (newViewportEnd > oldViewportEnd &&
+ newExtendedViewportEnd - newViewportEnd < bufferSize)
+ {
+ // Edge case: We're at the last item with excess measurement space.
+ // Skip re-measuring since we're at the list end and it won't change the result.
+ // This prevents redundant Measure-Arrange cycles when at list beginning.
+ nearingEdge = !_hasReachedEnd;
+ }
+ }
+ else
+ {
+ nearingEdge = true;
+ }
+
+ needsMeasure = nearingEdge;
+ }
+ }
+
+ if (needsMeasure)
+ {
+ // only store the new "old" extended viewport if we _did_ actually measure
+ _extendedViewport = extendedViewPort;
+
InvalidateMeasure();
}
}
@@ -924,6 +1108,15 @@ namespace Avalonia.Controls
}
}
+ private void OnCacheLengthChanged(AvaloniaPropertyChangedEventArgs e)
+ {
+ var newValue = e.GetNewValue();
+ _bufferFactor = newValue;
+
+ // Force a recalculation of the extended viewport on the next layout pass
+ InvalidateMeasure();
+ }
+
/// GetIrregularSnapPoints(Orientation orientation, SnapPointsAlignment snapPointsAlignment)
{
diff --git a/tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests.cs b/tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests.cs
index 0b33239687..6c6252d836 100644
--- a/tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests.cs
@@ -3,6 +3,7 @@ using System.Collections;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Collections.Specialized;
+using System.Diagnostics;
using System.Linq;
using Avalonia.Collections;
using Avalonia.Controls.Presenters;
@@ -24,137 +25,167 @@ namespace Avalonia.Controls.UnitTests
public class VirtualizingStackPanelTests : ScopedTestBase
{
private static FuncDataTemplate CanvasWithHeightTemplate = new((_, _) =>
- new Canvas
+ new CanvasCountingMeasureArrangeCalls
{
Width = 100,
[!Layoutable.HeightProperty] = new Binding("Height"),
});
private static FuncDataTemplate CanvasWithWidthTemplate = new((_, _) =>
- new Canvas
+ new CanvasCountingMeasureArrangeCalls
{
Height = 100,
[!Layoutable.WidthProperty] = new Binding("Width"),
});
- [Fact]
- public void Creates_Initial_Items()
+ [Theory]
+ [InlineData(0d , 10)]
+ [InlineData(0.5d, 20)]
+ public void Creates_Initial_Items(double bufferFactor, int expectedCount)
{
using var app = App();
- var (target, scroll, itemsControl) = CreateTarget();
+ var (target, scroll, itemsControl) = CreateTarget(bufferFactor:bufferFactor);
Assert.Equal(1000, scroll.Extent.Height);
- AssertRealizedItems(target, itemsControl, 0, 10);
+ AssertRealizedItems(target, itemsControl, 0, expectedCount);
}
- [Fact]
- public void Initializes_Initial_Control_Items()
+ [Theory]
+ [InlineData(0d, 10)]
+ [InlineData(0.5d, 20)] // Buffer factor of 0.5. Since at start there is no room, the 10 additional items are just appended
+ public void Initializes_Initial_Control_Items(double bufferFactor, int expectedCount)
{
using var app = App();
var items = Enumerable.Range(0, 100).Select(x => new Button { Width = 25, Height = 10 });
- var (target, scroll, itemsControl) = CreateTarget(items: items, itemTemplate: null);
+ var (target, scroll, itemsControl) = CreateTarget(items: items, itemTemplate: null, bufferFactor:bufferFactor);
Assert.Equal(1000, scroll.Extent.Height);
- AssertRealizedControlItems(target, itemsControl, 0, 10);
+ AssertRealizedControlItems(target, itemsControl, 0, expectedCount);
}
- [Fact]
- public void Creates_Reassigned_Items()
+ [Theory]
+ [InlineData(0d, 2)]
+ [InlineData(0.5d, 2)]
+ public void Creates_Reassigned_Items(double bufferFactor, int expectedCount)
{
using var app = App();
- var (target, scroll, itemsControl) = CreateTarget(items: Array.Empty());
+ var (target, scroll, itemsControl) = CreateTarget(items: Array.Empty(), bufferFactor: bufferFactor);
Assert.Empty(itemsControl.GetRealizedContainers());
itemsControl.ItemsSource = new[] { "foo", "bar" };
Layout(target);
- AssertRealizedItems(target, itemsControl, 0, 2);
+ AssertRealizedItems(target, itemsControl, 0, expectedCount);
}
- [Fact]
- public void Scrolls_Down_One_Item()
+ [Theory]
+ [InlineData(0d, 1, 10)]
+ [InlineData(0.5d, 0, 20)]
+ public void Scrolls_Down_One_Item(double bufferFactor, int expectedFirstIndex, int expectedCount)
{
using var app = App();
- var (target, scroll, itemsControl) = CreateTarget();
+ var (target, scroll, itemsControl) = CreateTarget(bufferFactor:bufferFactor);
scroll.Offset = new Vector(0, 10);
Layout(target);
- AssertRealizedItems(target, itemsControl, 1, 10);
+ AssertRealizedItems(target, itemsControl, expectedFirstIndex, expectedCount);
}
- [Fact]
- public void Scrolls_Down_More_Than_A_Page()
+ [Theory]
+ [InlineData(0d, 20,10)]
+ [InlineData(0.5d, 15,20)]
+ public void Scrolls_Down_More_Than_A_Page(double bufferFactor, int expectedFirstIndex, int expectedCount)
{
using var app = App();
- var (target, scroll, itemsControl) = CreateTarget();
+ var (target, scroll, itemsControl) = CreateTarget(bufferFactor:bufferFactor);
scroll.Offset = new Vector(0, 200);
Layout(target);
- AssertRealizedItems(target, itemsControl, 20, 10);
+ AssertRealizedItems(target, itemsControl, expectedFirstIndex, expectedCount);
}
- [Fact]
- public void Scrolls_Down_To_Index()
+ [Theory]
+ [InlineData(0d, 11, 10)]
+ [InlineData(0.5d, 6, 20)]
+ public void Scrolls_Down_To_Index(double bufferFactor, int expectedFirstIndex, int expectedCount)
{
using var app = App();
- var (target, scroll, itemsControl) = CreateTarget();
+ var (target, scroll, itemsControl) = CreateTarget(bufferFactor: bufferFactor);
target.ScrollIntoView(20);
- AssertRealizedItems(target, itemsControl, 11, 10);
+ AssertRealizedItems(target, itemsControl, expectedFirstIndex, expectedCount);
}
- [Fact]
- public void Scrolls_Up_To_Index()
+ [Theory]
+ [InlineData(0d, 90, 20, 10)]
+ [InlineData(0.5d, 80, 15, 20)]
+ public void Scrolls_Up_To_Index(double bufferFactor, int firstRealizedIndex, int expectedFirstIndex, int expectedCount)
{
using var app = App();
- var (target, scroll, itemsControl) = CreateTarget();
+ var (target, scroll, itemsControl) = CreateTarget(bufferFactor:bufferFactor);
scroll.ScrollToEnd();
Layout(target);
- Assert.Equal(90, target.FirstRealizedIndex);
+ Assert.Equal(firstRealizedIndex, target.FirstRealizedIndex);
target.ScrollIntoView(20);
- AssertRealizedItems(target, itemsControl, 20, 10);
+ AssertRealizedItems(target, itemsControl, expectedFirstIndex, expectedCount);
}
- [Fact]
- public void Scrolling_Up_To_Index_Does_Not_Create_A_Page_Of_Unrealized_Elements()
+ [Theory]
+ [InlineData(0d, 11)]
+ [InlineData(0.5d, 21)]
+ public void Scrolling_Up_To_Index_Does_Not_Create_A_Page_Of_Unrealized_Elements(double bufferFactor, int expectedCount)
{
using var app = App();
- var (target, scroll, itemsControl) = CreateTarget();
+ var (target, scroll, itemsControl) = CreateTarget(bufferFactor:bufferFactor);
scroll.ScrollToEnd();
Layout(target);
target.ScrollIntoView(20);
- Assert.Equal(11, target.Children.Count);
- }
-
- [Fact]
- public void Creates_Elements_On_Item_Insert_1()
+ Assert.Equal(expectedCount, target.Children.Count);
+ }
+
+ [Theory]
+ [InlineData(0d,
+ 10,
+ 11,
+ "-1, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10",
+ 10)]
+ [InlineData(0.5d,
+ 20,
+ 21,
+ "-1, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20",
+ 20)]
+ public void Creates_Elements_On_Item_Insert_1(double bufferFactor,
+ int firstCount,
+ int secondCount,
+ string indexesRaw,
+ int thirdCount)
{
using var app = App();
- var (target, _, itemsControl) = CreateTarget();
+ var (target, _, itemsControl) = CreateTarget(bufferFactor:bufferFactor);
var items = (IList)itemsControl.ItemsSource!;
- Assert.Equal(10, target.GetRealizedElements().Count);
+ Assert.Equal(firstCount, target.GetRealizedElements().Count);
items.Insert(0, "new");
- Assert.Equal(11, target.GetRealizedElements().Count);
+ Assert.Equal(secondCount, target.GetRealizedElements().Count);
var indexes = GetRealizedIndexes(target, itemsControl);
// Blank space inserted in realized elements and subsequent indexes updated.
- Assert.Equal(new[] { -1, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 }, indexes);
+ Assert.Equal(indexesRaw.Split(", ").Select(Int32.Parse).ToArray(), indexes);
var elements = target.GetRealizedElements().ToList();
Layout(target);
@@ -162,7 +193,7 @@ namespace Avalonia.Controls.UnitTests
indexes = GetRealizedIndexes(target, itemsControl);
// After layout an element for the new element is created.
- Assert.Equal(Enumerable.Range(0, 10), indexes);
+ Assert.Equal(Enumerable.Range(0, thirdCount), indexes);
// But apart from the new element and the removed last element, all existing elements
// should be the same.
@@ -171,23 +202,37 @@ namespace Avalonia.Controls.UnitTests
Assert.Equal(elements, target.GetRealizedElements());
}
- [Fact]
- public void Creates_Elements_On_Item_Insert_2()
+ [Theory]
+ [InlineData(0d,
+ 10,
+ 11,
+ "0, 1, -1, 3, 4, 5, 6, 7, 8, 9, 10",
+ 10)]
+ [InlineData(0.5d,
+ 20,
+ 21,
+ "0, 1, -1, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20",
+ 20)]
+ public void Creates_Elements_On_Item_Insert_2(double bufferFactor,
+ int firstCount,
+ int secondCount,
+ string indexesRaw,
+ int thirdCount)
{
using var app = App();
- var (target, _, itemsControl) = CreateTarget();
+ var (target, _, itemsControl) = CreateTarget(bufferFactor:bufferFactor);
var items = (IList)itemsControl.ItemsSource!;
- Assert.Equal(10, target.GetRealizedElements().Count);
+ Assert.Equal(firstCount, target.GetRealizedElements().Count);
items.Insert(2, "new");
- Assert.Equal(11, target.GetRealizedElements().Count);
+ Assert.Equal(secondCount, target.GetRealizedElements().Count);
var indexes = GetRealizedIndexes(target, itemsControl);
// Blank space inserted in realized elements and subsequent indexes updated.
- Assert.Equal(new[] { 0, 1, -1, 3, 4, 5, 6, 7, 8, 9, 10 }, indexes);
+ Assert.Equal(indexesRaw.Split(", ").Select(Int32.Parse).ToArray(), indexes);
var elements = target.GetRealizedElements().ToList();
Layout(target);
@@ -195,7 +240,7 @@ namespace Avalonia.Controls.UnitTests
indexes = GetRealizedIndexes(target, itemsControl);
// After layout an element for the new element is created.
- Assert.Equal(Enumerable.Range(0, 10), indexes);
+ Assert.Equal(Enumerable.Range(0, thirdCount), indexes);
// But apart from the new element and the removed last element, all existing elements
// should be the same.
@@ -204,8 +249,10 @@ namespace Avalonia.Controls.UnitTests
Assert.Equal(elements, target.GetRealizedElements());
}
- [Fact]
- public void Updates_Elements_On_Item_Moved()
+ [Theory]
+ [InlineData(0d)]
+ [InlineData(0.5d)]
+ public void Updates_Elements_On_Item_Moved(double bufferFactor)
{
// Arrange
@@ -215,7 +262,7 @@ namespace Avalonia.Controls.UnitTests
.Range(0, 100)
.Select(x => $"Item {x}"));
- var (target, _, itemsControl) = CreateTarget(items: actualItems);
+ var (target, _, itemsControl) = CreateTarget(items: actualItems, bufferFactor:bufferFactor);
var expectedRealizedElementContents = new[] { 1, 2, 0, 3, 4, 5, 6, 7, 8, 9 }
.Select(x => $"Item {x}");
@@ -235,8 +282,10 @@ namespace Avalonia.Controls.UnitTests
Assert.Equivalent(expectedRealizedElementContents, actualRealizedElementContents);
}
- [Fact]
- public void Updates_Elements_On_Item_Range_Moved()
+ [Theory]
+ [InlineData(0d)]
+ [InlineData(0.5d)]
+ public void Updates_Elements_On_Item_Range_Moved(double bufferFactor)
{
// Arrange
@@ -246,7 +295,7 @@ namespace Avalonia.Controls.UnitTests
.Range(0, 100)
.Select(x => $"Item {x}"));
- var (target, _, itemsControl) = CreateTarget(items: actualItems);
+ var (target, _, itemsControl) = CreateTarget(items: actualItems, bufferFactor: bufferFactor);
var expectedRealizedElementContents = new[] { 2, 0, 1, 3, 4, 5, 6, 7, 8, 9 }
.Select(x => $"Item {x}");
@@ -266,14 +315,16 @@ namespace Avalonia.Controls.UnitTests
Assert.Equivalent(expectedRealizedElementContents, actualRealizedElementContents);
}
- [Fact]
- public void Updates_Elements_On_Item_Remove()
+ [Theory]
+ [InlineData(0d, 10, 9)]
+ [InlineData(0.5d, 20, 19)]
+ public void Updates_Elements_On_Item_Remove(double bufferFactor, int firstCount, int secondCount)
{
using var app = App();
- var (target, _, itemsControl) = CreateTarget();
+ var (target, _, itemsControl) = CreateTarget(bufferFactor: bufferFactor);
var items = (IList)itemsControl.ItemsSource!;
- Assert.Equal(10, target.GetRealizedElements().Count);
+ Assert.Equal(firstCount, target.GetRealizedElements().Count);
var toRecycle = target.GetRealizedElements().ElementAt(2);
items.RemoveAt(2);
@@ -281,7 +332,7 @@ namespace Avalonia.Controls.UnitTests
var indexes = GetRealizedIndexes(target, itemsControl);
// Item removed from realized elements and subsequent row indexes updated.
- Assert.Equal(Enumerable.Range(0, 9), indexes);
+ Assert.Equal(Enumerable.Range(0, secondCount), indexes);
var elements = target.GetRealizedElements().ToList();
Layout(target);
@@ -289,21 +340,23 @@ namespace Avalonia.Controls.UnitTests
indexes = GetRealizedIndexes(target, itemsControl);
// After layout an element for the newly visible last row is created and indexes updated.
- Assert.Equal(Enumerable.Range(0, 10), indexes);
+ Assert.Equal(Enumerable.Range(0, firstCount), indexes);
// And the removed row should now have been recycled as the last row.
elements.Add(toRecycle);
Assert.Equal(elements, target.GetRealizedElements());
}
- [Fact]
- public void Updates_Elements_On_Item_Replace()
+ [Theory]
+ [InlineData(0d, 10, "0, 1, -1, 3, 4, 5, 6, 7, 8, 9")]
+ [InlineData(0.5d, 20, "0, 1, -1, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19")]
+ public void Updates_Elements_On_Item_Replace(double bufferFactor, int firstCount, string indexesRaw)
{
using var app = App();
- var (target, _, itemsControl) = CreateTarget();
+ var (target, _, itemsControl) = CreateTarget(bufferFactor: bufferFactor);
var items = (ObservableCollection)itemsControl.ItemsSource!;
- Assert.Equal(10, target.GetRealizedElements().Count);
+ Assert.Equal(firstCount, target.GetRealizedElements().Count);
var toReplace = target.GetRealizedElements().ElementAt(2);
items[2] = "new";
@@ -315,24 +368,26 @@ namespace Avalonia.Controls.UnitTests
var indexes = GetRealizedIndexes(target, itemsControl);
// Item removed from realized elements at old position and space inserted at new position.
- Assert.Equal(new[] { 0, 1, -1, 3, 4, 5, 6, 7, 8, 9 }, indexes);
+ Assert.Equal(indexesRaw.Split(", ").Select(Int32.Parse).ToArray(), indexes);
Layout(target);
indexes = GetRealizedIndexes(target, itemsControl);
// After layout the missing container should have been created.
- Assert.Equal(Enumerable.Range(0, 10), indexes);
+ Assert.Equal(Enumerable.Range(0, firstCount), indexes);
}
- [Fact]
- public void Updates_Elements_On_Item_Move()
+ [Theory]
+ [InlineData(0d, 10, "0, 1, 2, 3, 4, 5, -1, 7, 8, 9")]
+ [InlineData(0.5d, 20, "0, 1, 2, 3, 4, 5, -1, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19")]
+ public void Updates_Elements_On_Item_Move(double bufferFactor, int firstCount, string indexesRaw)
{
using var app = App();
- var (target, _, itemsControl) = CreateTarget();
+ var (target, _, itemsControl) = CreateTarget(bufferFactor:bufferFactor);
var items = (ObservableCollection)itemsControl.ItemsSource!;
- Assert.Equal(10, target.GetRealizedElements().Count);
+ Assert.Equal(firstCount, target.GetRealizedElements().Count);
var toMove = target.GetRealizedElements().ElementAt(2);
items.Move(2, 6);
@@ -344,22 +399,24 @@ namespace Avalonia.Controls.UnitTests
var indexes = GetRealizedIndexes(target, itemsControl);
// Item removed from realized elements at old position and space inserted at new position.
- Assert.Equal(new[] { 0, 1, 2, 3, 4, 5, -1, 7, 8, 9 }, indexes);
+ Assert.Equal(indexesRaw.Split(", ").Select(Int32.Parse).ToArray(), indexes);
Layout(target);
indexes = GetRealizedIndexes(target, itemsControl);
// After layout the missing container should have been created.
- Assert.Equal(Enumerable.Range(0, 10), indexes);
+ Assert.Equal(Enumerable.Range(0, firstCount), indexes);
}
-
- [Fact]
- public void Removes_Control_Items_From_Panel_On_Item_Remove()
+
+ [Theory]
+ [InlineData(0d)]
+ [InlineData(0.5d)]
+ public void Removes_Control_Items_From_Panel_On_Item_Remove(double bufferFactor)
{
using var app = App();
var items = new ObservableCollection(Enumerable.Range(0, 100).Select(x => new Button { Width = 25, Height = 10 }));
- var (target, scroll, itemsControl) = CreateTarget(items: items, itemTemplate: null);
+ var (target, scroll, itemsControl) = CreateTarget(items: items, itemTemplate: null, bufferFactor:bufferFactor);
Assert.Equal(1000, scroll.Extent.Height);
@@ -370,11 +427,13 @@ namespace Avalonia.Controls.UnitTests
Assert.Null(removed.VisualParent);
}
- [Fact]
- public void Does_Not_Recycle_Focused_Element()
+ [Theory]
+ [InlineData(0d)]
+ [InlineData(0.5d)]
+ public void Does_Not_Recycle_Focused_Element(double bufferFactor)
{
using var app = App();
- var (target, scroll, itemsControl) = CreateTarget();
+ var (target, scroll, itemsControl) = CreateTarget(bufferFactor: bufferFactor);
var focused = target.GetRealizedElements().First()!;
focused.Focusable = true;
@@ -387,11 +446,13 @@ namespace Avalonia.Controls.UnitTests
Assert.All(target.GetRealizedElements(), x => Assert.False(x!.IsKeyboardFocusWithin));
}
- [Fact]
- public void Removing_Item_Of_Focused_Element_Clears_Focus()
+ [Theory]
+ [InlineData(0d)]
+ [InlineData(0.5d)]
+ public void Removing_Item_Of_Focused_Element_Clears_Focus(double bufferFactor)
{
using var app = App();
- var (target, scroll, itemsControl) = CreateTarget();
+ var (target, scroll, itemsControl) = CreateTarget(bufferFactor: bufferFactor);
var items = (IList)itemsControl.ItemsSource!;
var focused = target.GetRealizedElements().First()!;
@@ -409,11 +470,13 @@ namespace Avalonia.Controls.UnitTests
Assert.All(target.GetRealizedElements(), x => Assert.NotSame(focused, x));
}
- [Fact]
- public void Scrolling_Back_To_Focused_Element_Uses_Correct_Element()
+ [Theory]
+ [InlineData(0d)]
+ [InlineData(0.5d)]
+ public void Scrolling_Back_To_Focused_Element_Uses_Correct_Element(double bufferFactor)
{
using var app = App();
- var (target, scroll, itemsControl) = CreateTarget();
+ var (target, scroll, itemsControl) = CreateTarget(bufferFactor: bufferFactor);
var focused = target.GetRealizedElements().First()!;
focused.Focusable = true;
@@ -429,11 +492,13 @@ namespace Avalonia.Controls.UnitTests
Assert.Same(focused, target.GetRealizedElements().First());
}
- [Fact]
- public void Focusing_Another_Element_Recycles_Original_Focus_Element()
+ [Theory]
+ [InlineData(0d)]
+ [InlineData(0.5d)]
+ public void Focusing_Another_Element_Recycles_Original_Focus_Element(double bufferFactor)
{
using var app = App();
- var (target, scroll, itemsControl) = CreateTarget();
+ var (target, scroll, itemsControl) = CreateTarget(bufferFactor: bufferFactor);
var originalFocused = target.GetRealizedElements().First()!;
originalFocused.Focusable = true;
@@ -449,11 +514,13 @@ namespace Avalonia.Controls.UnitTests
Assert.False(originalFocused.IsVisible);
}
- [Fact]
- public void Focused_Element_Losing_Focus_Does_Not_Reset_Selection()
+ [Theory]
+ [InlineData(0d)]
+ [InlineData(0.5d)]
+ public void Focused_Element_Losing_Focus_Does_Not_Reset_Selection(double bufferFactor)
{
using var app = App();
- var (target, scroll, listBox) = CreateTarget(
+ var (target, scroll, listBox) = CreateTarget(
styles: new[]
{
new Style(x => x.OfType())
@@ -463,7 +530,7 @@ namespace Avalonia.Controls.UnitTests
new Setter(ListBoxItem.TemplateProperty, ListBoxItemTemplate()),
}
}
- });
+ }, bufferFactor: bufferFactor);
listBox.SelectedIndex = 0;
@@ -481,36 +548,40 @@ namespace Avalonia.Controls.UnitTests
Assert.Equal(0, listBox.SelectedIndex);
}
- [Fact]
- public void Removing_Range_When_Scrolled_To_End_Updates_Viewport()
+ [Theory]
+ [InlineData(0d, 90, 10, 10)]
+ [InlineData(0.5d, 80, 0, 20)]
+ public void Removing_Range_When_Scrolled_To_End_Updates_Viewport(double bufferFactor, int firstIndex, int secondIndex, int count)
{
using var app = App();
var items = new AvaloniaList(Enumerable.Range(0, 100).Select(x => $"Item {x}"));
- var (target, scroll, itemsControl) = CreateTarget(items: items);
+ var (target, scroll, itemsControl) = CreateTarget(items: items, bufferFactor: bufferFactor);
scroll.Offset = new Vector(0, 900);
Layout(target);
- AssertRealizedItems(target, itemsControl, 90, 10);
+ AssertRealizedItems(target, itemsControl, firstIndex, count);
items.RemoveRange(0, 80);
Layout(target);
- AssertRealizedItems(target, itemsControl, 10, 10);
+ AssertRealizedItems(target, itemsControl, secondIndex, count);
Assert.Equal(new Vector(0, 100), scroll.Offset);
}
- [Fact]
- public void Removing_Range_To_Have_Less_Than_A_Page_Of_Items_When_Scrolled_To_End_Updates_Viewport()
+ [Theory]
+ [InlineData(0d, 90, 10)]
+ [InlineData(0.5d, 80, 20)]
+ public void Removing_Range_To_Have_Less_Than_A_Page_Of_Items_When_Scrolled_To_End_Updates_Viewport(double bufferFactor, int firstIndex, int count)
{
using var app = App();
var items = new AvaloniaList(Enumerable.Range(0, 100).Select(x => $"Item {x}"));
- var (target, scroll, itemsControl) = CreateTarget(items: items);
+ var (target, scroll, itemsControl) = CreateTarget(items: items, bufferFactor: bufferFactor);
scroll.Offset = new Vector(0, 900);
Layout(target);
- AssertRealizedItems(target, itemsControl, 90, 10);
+ AssertRealizedItems(target, itemsControl, firstIndex, count);
items.RemoveRange(0, 95);
Layout(target);
@@ -519,36 +590,40 @@ namespace Avalonia.Controls.UnitTests
Assert.Equal(new Vector(0, 0), scroll.Offset);
}
- [Fact]
- public void Resetting_Collection_To_Have_Less_Items_When_Scrolled_To_End_Updates_Viewport()
+ [Theory]
+ [InlineData(0d, 90, 10, 10)]
+ [InlineData(0.5d, 80,0, 20)]
+ public void Resetting_Collection_To_Have_Less_Items_When_Scrolled_To_End_Updates_Viewport(double bufferFactor, int firstIndex, int secondIndex, int count)
{
using var app = App();
var items = new ResettingCollection(Enumerable.Range(0, 100).Select(x => $"Item {x}"));
- var (target, scroll, itemsControl) = CreateTarget(items: items);
+ var (target, scroll, itemsControl) = CreateTarget(items: items, bufferFactor: bufferFactor);
scroll.Offset = new Vector(0, 900);
Layout(target);
- AssertRealizedItems(target, itemsControl, 90, 10);
+ AssertRealizedItems(target, itemsControl, firstIndex, count);
items.Reset(Enumerable.Range(0, 20).Select(x => $"Item {x}"));
Layout(target);
- AssertRealizedItems(target, itemsControl, 10, 10);
+ AssertRealizedItems(target, itemsControl, secondIndex, count);
Assert.Equal(new Vector(0, 100), scroll.Offset);
}
- [Fact]
- public void Resetting_Collection_To_Have_Less_Than_A_Page_Of_Items_When_Scrolled_To_End_Updates_Viewport()
+ [Theory]
+ [InlineData(0d, 90, 10)]
+ [InlineData(0.5d, 80, 20)]
+ public void Resetting_Collection_To_Have_Less_Than_A_Page_Of_Items_When_Scrolled_To_End_Updates_Viewport(double bufferFactor, int firstIndex, int count)
{
using var app = App();
var items = new ResettingCollection(Enumerable.Range(0, 100).Select(x => $"Item {x}"));
- var (target, scroll, itemsControl) = CreateTarget(items: items);
+ var (target, scroll, itemsControl) = CreateTarget(items: items, bufferFactor: bufferFactor);
scroll.Offset = new Vector(0, 900);
Layout(target);
- AssertRealizedItems(target, itemsControl, 90, 10);
+ AssertRealizedItems(target, itemsControl, firstIndex, count);
items.Reset(Enumerable.Range(0, 5).Select(x => $"Item {x}"));
Layout(target);
@@ -557,8 +632,10 @@ namespace Avalonia.Controls.UnitTests
Assert.Equal(new Vector(0, 0), scroll.Offset);
}
- [Fact]
- public void NthChild_Selector_Works()
+ [Theory]
+ [InlineData(0d, 10, "4,9")]
+ [InlineData(0.5d, 20, "4,9,14,19")]
+ public void NthChild_Selector_Works(double bufferFactor, int count, string indexesRaw)
{
using var app = App();
@@ -567,16 +644,17 @@ namespace Avalonia.Controls.UnitTests
Setters = { new Setter(ListBoxItem.BackgroundProperty, Brushes.Red) },
};
- var (target, _, _) = CreateTarget(styles: new[] { style });
+ var (target, _, _) = CreateTarget(styles: new[] { style }, bufferFactor: bufferFactor);
var realized = target.GetRealizedContainers()!.Cast().ToList();
- Assert.Equal(10, realized.Count);
+ Assert.Equal(count, realized.Count);
- for (var i = 0; i < 10; ++i)
+ for (var i = 0; i < count; ++i)
{
var container = realized[i];
var index = target.IndexFromContainer(container);
- var expectedBackground = (i == 4 || i == 9) ? Brushes.Red : null;
+ var redIndexes = indexesRaw.Split(",").Select(Int32.Parse).ToArray();
+ var expectedBackground = redIndexes.Contains(i) ? Brushes.Red : null;
Assert.Equal(i, index);
Assert.Equal(expectedBackground, container.Background);
@@ -584,8 +662,10 @@ namespace Avalonia.Controls.UnitTests
}
// https://github.com/AvaloniaUI/Avalonia/issues/12838
- [Fact]
- public void NthChild_Selector_Works_For_ItemTemplate_Children()
+ [Theory]
+ [InlineData(0d, 10, "4,9")]
+ [InlineData(0.5d, 20, "4,9,14,19")]
+ public void NthChild_Selector_Works_For_ItemTemplate_Children(double bufferFactor, int count, string indexesRaw)
{
using var app = App();
@@ -594,24 +674,27 @@ namespace Avalonia.Controls.UnitTests
Setters = { new Setter(Panel.BackgroundProperty, Brushes.Red) },
};
- var (target, _, _) = CreateTarget(styles: new[] { style });
+ var (target, _, _) = CreateTarget(styles: new[] { style }, bufferFactor: bufferFactor);
var realized = target.GetRealizedContainers()!.Cast().ToList();
- Assert.Equal(10, realized.Count);
+ Assert.Equal(count, realized.Count);
- for (var i = 0; i < 10; ++i)
+ for (var i = 0; i < count; ++i)
{
var container = realized[i];
var index = target.IndexFromContainer(container);
- var expectedBackground = (i == 4 || i == 9) ? Brushes.Red : null;
+ var redIndexes = indexesRaw.Split(",").Select(Int32.Parse).ToArray();
+ var expectedBackground = redIndexes.Contains(i) ? Brushes.Red : null;
Assert.Equal(i, index);
Assert.Equal(expectedBackground, ((Canvas)container.Child!).Background);
}
}
- [Fact]
- public void NthLastChild_Selector_Works()
+ [Theory]
+ [InlineData(0d, 10, "0,5")]
+ [InlineData(0.5d, 20, "0,5,10,15")]
+ public void NthLastChild_Selector_Works(double bufferFactor, int count, string indexesRaw)
{
using var app = App();
@@ -620,16 +703,17 @@ namespace Avalonia.Controls.UnitTests
Setters = { new Setter(ListBoxItem.BackgroundProperty, Brushes.Red) },
};
- var (target, _, _) = CreateTarget(styles: new[] { style });
+ var (target, _, _) = CreateTarget(styles: new[] { style }, bufferFactor: bufferFactor);
var realized = target.GetRealizedContainers()!.Cast().ToList();
- Assert.Equal(10, realized.Count);
+ Assert.Equal(count, realized.Count);
- for (var i = 0; i < 10; ++i)
+ for (var i = 0; i < count; ++i)
{
var container = realized[i];
var index = target.IndexFromContainer(container);
- var expectedBackground = (i == 0 || i == 5) ? Brushes.Red : null;
+ var redIndexes = indexesRaw.Split(",").Select(Int32.Parse).ToArray();
+ var expectedBackground = redIndexes.Contains(i) ? Brushes.Red : null;
Assert.Equal(i, index);
Assert.Equal(expectedBackground, container.Background);
@@ -637,8 +721,10 @@ namespace Avalonia.Controls.UnitTests
}
// https://github.com/AvaloniaUI/Avalonia/issues/12838
- [Fact]
- public void NthLastChild_Selector_Works_For_ItemTemplate_Children()
+ [Theory]
+ [InlineData(0d, 10, "0,5")]
+ [InlineData(0.5d, 20, "0,5,10,15")]
+ public void NthLastChild_Selector_Works_For_ItemTemplate_Children(double bufferFactor, int count, string indexesRaw)
{
using var app = App();
@@ -647,27 +733,30 @@ namespace Avalonia.Controls.UnitTests
Setters = { new Setter(Panel.BackgroundProperty, Brushes.Red) },
};
- var (target, _, _) = CreateTarget(styles: new[] { style });
+ var (target, _, _) = CreateTarget(styles: new[] { style }, bufferFactor: bufferFactor);
var realized = target.GetRealizedContainers()!.Cast().ToList();
- Assert.Equal(10, realized.Count);
+ Assert.Equal(count, realized.Count);
- for (var i = 0; i < 10; ++i)
+ for (var i = 0; i < count; ++i)
{
var container = realized[i];
var index = target.IndexFromContainer(container);
- var expectedBackground = (i == 0 || i == 5) ? Brushes.Red : null;
+ var redIndexes = indexesRaw.Split(",").Select(Int32.Parse).ToArray();
+ var expectedBackground = redIndexes.Contains(i) ? Brushes.Red : null;
Assert.Equal(i, index);
Assert.Equal(expectedBackground, ((Canvas)container.Child!).Background);
}
}
- [Fact]
- public void ContainerPrepared_Is_Raised_When_Scrolling()
+ [Theory]
+ [InlineData(0d, 10)]
+ [InlineData(0.5d, 15)]
+ public void ContainerPrepared_Is_Raised_When_Scrolling(double bufferFactor, int expectedRaised)
{
using var app = App();
- var (target, scroll, itemsControl) = CreateTarget();
+ var (target, scroll, itemsControl) = CreateTarget(bufferFactor: bufferFactor);
var raised = 0;
itemsControl.ContainerPrepared += (s, e) => ++raised;
@@ -675,14 +764,16 @@ namespace Avalonia.Controls.UnitTests
scroll.Offset = new Vector(0, 200);
Layout(target);
- Assert.Equal(10, raised);
+ Assert.Equal(expectedRaised, raised);
}
- [Fact]
- public void ContainerClearing_Is_Raised_When_Scrolling()
+ [Theory]
+ [InlineData(0d, 10)]
+ [InlineData(0.5d, 15)]
+ public void ContainerClearing_Is_Raised_When_Scrolling(double bufferFactor, int expectedRaised)
{
using var app = App();
- var (target, scroll, itemsControl) = CreateTarget();
+ var (target, scroll, itemsControl) = CreateTarget(bufferFactor: bufferFactor);
var raised = 0;
itemsControl.ContainerClearing += (s, e) => ++raised;
@@ -690,14 +781,16 @@ namespace Avalonia.Controls.UnitTests
scroll.Offset = new Vector(0, 200);
Layout(target);
- Assert.Equal(10, raised);
+ Assert.Equal(expectedRaised, raised);
}
- [Fact]
- public void ContainerIndexChanged_Is_Raised_On_Insert()
+ [Theory]
+ [InlineData(0d, 9)]
+ [InlineData(0.5d, 19)]
+ public void ContainerIndexChanged_Is_Raised_On_Insert(double bufferFactor, int expectedRaised)
{
using var app = App();
- var (target, scroll, itemsControl) = CreateTarget();
+ var (target, scroll, itemsControl) = CreateTarget(bufferFactor: bufferFactor);
var items = (IList)itemsControl.ItemsSource!;
var raised = 0;
var index = 1;
@@ -711,17 +804,18 @@ namespace Avalonia.Controls.UnitTests
items.Insert(index, "new");
- Assert.Equal(9, raised);
+ Assert.Equal(expectedRaised, raised);
}
- [Fact]
- public void ContainerIndexChanged_Is_Raised_When_Item_Inserted_Before_Realized_Elements()
+ [Theory]
+ [InlineData(0d, 10, 20)]
+ [InlineData(0.5d, 20, 15)]
+ public void ContainerIndexChanged_Is_Raised_When_Item_Inserted_Before_Realized_Elements(double bufferFactor, int expectedRaised, int index)
{
using var app = App();
- var (target, scroll, itemsControl) = CreateTarget();
+ var (target, scroll, itemsControl) = CreateTarget(bufferFactor: bufferFactor);
var items = (IList)itemsControl.ItemsSource!;
var raised = 0;
- var index = 20;
itemsControl.ContainerIndexChanged += (s, e) =>
{
@@ -735,14 +829,16 @@ namespace Avalonia.Controls.UnitTests
items.Insert(10, "new");
- Assert.Equal(10, raised);
+ Assert.Equal(expectedRaised, raised);
}
- [Fact]
- public void ContainerIndexChanged_Is_Raised_On_Remove()
+ [Theory]
+ [InlineData(0d, 8)]
+ [InlineData(0.5d, 18)]
+ public void ContainerIndexChanged_Is_Raised_On_Remove(double bufferFactor, int expectedRaised)
{
using var app = App();
- var (target, scroll, itemsControl) = CreateTarget();
+ var (target, scroll, itemsControl) = CreateTarget(bufferFactor: bufferFactor);
var items = (IList)itemsControl.ItemsSource!;
var raised = 0;
var index = 1;
@@ -756,17 +852,18 @@ namespace Avalonia.Controls.UnitTests
items.RemoveAt(index);
- Assert.Equal(8, raised);
+ Assert.Equal(expectedRaised, raised);
}
- [Fact]
- public void ContainerIndexChanged_Is_Raised_When_Item_Removed_Before_Realized_Elements()
+ [Theory]
+ [InlineData(0d, 10, 20)]
+ [InlineData(0.5d, 20, 15)]
+ public void ContainerIndexChanged_Is_Raised_When_Item_Removed_Before_Realized_Elements(double bufferFactor, int expectedRaised, int index)
{
using var app = App();
- var (target, scroll, itemsControl) = CreateTarget();
+ var (target, scroll, itemsControl) = CreateTarget(bufferFactor: bufferFactor);
var items = (IList)itemsControl.ItemsSource!;
var raised = 0;
- var index = 20;
itemsControl.ContainerIndexChanged += (s, e) =>
{
@@ -781,14 +878,16 @@ namespace Avalonia.Controls.UnitTests
items.RemoveAt(10);
- Assert.Equal(10, raised);
+ Assert.Equal(expectedRaised, raised);
}
- [Fact]
- public void Fires_Correct_Container_Lifecycle_Events_On_Replace()
+ [Theory]
+ [InlineData(0d)]
+ [InlineData(0.5d)]
+ public void Fires_Correct_Container_Lifecycle_Events_On_Replace(double bufferFactor)
{
using var app = App();
- var (target, scroll, itemsControl) = CreateTarget();
+ var (target, scroll, itemsControl) = CreateTarget(bufferFactor: bufferFactor);
var items = (IList)itemsControl.ItemsSource!;
var events = new List();
@@ -812,15 +911,17 @@ namespace Avalonia.Controls.UnitTests
events.Clear();
}
- [Fact]
- public void Scrolling_Down_With_Larger_Element_Does_Not_Cause_Jump_And_Arrives_At_End()
+ [Theory]
+ [InlineData(0d)]
+ [InlineData(0.5d)]
+ public void Scrolling_Down_With_Larger_Element_Does_Not_Cause_Jump_And_Arrives_At_End(double bufferFactor)
{
using var app = App();
var items = Enumerable.Range(0, 1000).Select(x => new ItemWithHeight(x)).ToList();
items[20].Height = 200;
- var (target, scroll, itemsControl) = CreateTarget(items: items, itemTemplate: CanvasWithHeightTemplate);
+ var (target, scroll, itemsControl) = CreateTarget(items: items, itemTemplate: CanvasWithHeightTemplate, bufferFactor: bufferFactor);
var index = target.FirstRealizedIndex;
@@ -841,15 +942,17 @@ namespace Avalonia.Controls.UnitTests
}
}
- [Fact]
- public void Scrolling_Up_To_Larger_Element_Does_Not_Cause_Jump()
+ [Theory]
+ [InlineData(0d)]
+ [InlineData(0.5d)]
+ public void Scrolling_Up_To_Larger_Element_Does_Not_Cause_Jump(double bufferFactor)
{
using var app = App();
var items = Enumerable.Range(0, 100).Select(x => new ItemWithHeight(x)).ToList();
items[20].Height = 200;
- var (target, scroll, itemsControl) = CreateTarget(items: items, itemTemplate: CanvasWithHeightTemplate);
+ var (target, scroll, itemsControl) = CreateTarget(items: items, itemTemplate: CanvasWithHeightTemplate, bufferFactor: bufferFactor);
// Scroll past the larger element.
scroll.Offset = new Vector(0, 600);
@@ -871,15 +974,26 @@ namespace Avalonia.Controls.UnitTests
}
}
- [Fact]
- public void Scrolling_Up_To_Smaller_Element_Does_Not_Cause_Jump()
+ [Theory]
+ [InlineData(0d)]
+ [InlineData(0.5d)]
+ public void Scrolling_Up_To_Smaller_Element_Does_Not_Cause_Jump(double bufferFactor)
{
using var app = App();
var items = Enumerable.Range(0, 100).Select(x => new ItemWithHeight(x, 30)).ToList();
items[20].Height = 25;
- var (target, scroll, itemsControl) = CreateTarget(items: items, itemTemplate: CanvasWithHeightTemplate);
+ var (target, scroll, itemsControl) = CreateTarget(items: items,
+ itemTemplate: CanvasWithHeightTemplate,
+ bufferFactor: bufferFactor);
+
+ var additionalItemsCount = bufferFactor == 0d
+ ? 1
+ // buffer factor of 0.5 and 7 visible items => will be rounded up to 4
+ // => when we scroll up and are near the _extended_ viewport,
+ // 4 additional items will be inserted above the current viewport
+ : Math.Round(target.Children.Count * target.CacheLength, MidpointRounding.AwayFromZero);
// Scroll past the larger element.
scroll.Offset = new Vector(0, 25 * items[0].Height);
@@ -900,19 +1014,21 @@ namespace Avalonia.Controls.UnitTests
target.FirstRealizedIndex <= index,
$"{target.FirstRealizedIndex} is not less than {index}");
Assert.True(
- index - target.FirstRealizedIndex <= 1,
+ index - target.FirstRealizedIndex <= additionalItemsCount,
$"FirstIndex changed from {index} to {target.FirstRealizedIndex}");
index = target.FirstRealizedIndex;
}
}
- [Fact]
- public void Does_Not_Throw_When_Estimating_Viewport_With_Ancestor_Margin()
+ [Theory]
+ [InlineData(0d)]
+ [InlineData(0.5d)]
+ public void Does_Not_Throw_When_Estimating_Viewport_With_Ancestor_Margin(double bufferFactor)
{
// Issue #11272
using var app = App();
- var (_, _, itemsControl) = CreateUnrootedTarget();
+ var (_, _, itemsControl) = CreateUnrootedTarget(bufferFactor: bufferFactor);
var container = new Decorator { Margin = new Thickness(100) };
var root = new TestRoot(true, container);
@@ -923,17 +1039,19 @@ namespace Avalonia.Controls.UnitTests
root.LayoutManager.ExecuteLayoutPass();
}
- [Fact]
- public void Supports_Null_Recycle_Key_When_Scrolling()
+ [Theory]
+ [InlineData(0d, 20)]
+ [InlineData(0.5d, 200)]
+ public void Supports_Null_Recycle_Key_When_Scrolling(double bufferFactor, int offset)
{
using var app = App();
- var (_, scroll, itemsControl) = CreateUnrootedTarget();
+ var (_, scroll, itemsControl) = CreateUnrootedTarget(bufferFactor: bufferFactor);
var root = CreateRoot(itemsControl);
root.LayoutManager.ExecuteInitialLayoutPass();
var firstItem = itemsControl.ContainerFromIndex(0)!;
- scroll.Offset = new(0, 20);
+ scroll.Offset = new(0, offset);
Layout(itemsControl);
@@ -942,11 +1060,13 @@ namespace Avalonia.Controls.UnitTests
Assert.DoesNotContain(firstItem, itemsControl.ItemsPanelRoot!.Children);
}
- [Fact]
- public void Supports_Null_Recycle_Key_When_Clearing_Items()
+ [Theory]
+ [InlineData(0d)]
+ [InlineData(0.5d)]
+ public void Supports_Null_Recycle_Key_When_Clearing_Items(double bufferFactor)
{
using var app = App();
- var (_, _, itemsControl) = CreateUnrootedTarget();
+ var (_, _, itemsControl) = CreateUnrootedTarget(bufferFactor: bufferFactor);
var root = CreateRoot(itemsControl);
root.LayoutManager.ExecuteInitialLayoutPass();
@@ -961,11 +1081,13 @@ namespace Avalonia.Controls.UnitTests
Assert.Empty(itemsControl.ItemsPanelRoot!.Children);
}
- [Fact]
- public void ScrollIntoView_On_Effectively_Invisible_Panel_Does_Not_Create_Ghost_Elements()
+ [Theory]
+ [InlineData(0d)]
+ [InlineData(0.5d)]
+ public void ScrollIntoView_On_Effectively_Invisible_Panel_Does_Not_Create_Ghost_Elements(double bufferFactor)
{
var items = new[] { "foo", "bar", "baz" };
- var (target, _, itemsControl) = CreateUnrootedTarget(items: items);
+ var (target, _, itemsControl) = CreateUnrootedTarget(items: items, bufferFactor: bufferFactor);
var container = new Decorator { Margin = new Thickness(100), Child = itemsControl };
var root = new TestRoot(true, container);
@@ -996,11 +1118,13 @@ namespace Avalonia.Controls.UnitTests
}
// https://github.com/AvaloniaUI/Avalonia/issues/10968
- [Fact]
- public void Does_Not_Realize_Items_If_Self_Outside_Viewport()
+ [Theory]
+ [InlineData(0d)]
+ [InlineData(0.5d)]
+ public void Does_Not_Realize_Items_If_Self_Outside_Viewport(double bufferFactor)
{
using var app = App();
- var (panel, _, itemsControl) = CreateUnrootedTarget();
+ var (panel, _, itemsControl) = CreateUnrootedTarget(bufferFactor: bufferFactor);
itemsControl.Margin = new Thickness(0.0, 200.0, 0.0, 0.0);
var scrollContentPresenter = new ScrollContentPresenter
@@ -1023,8 +1147,14 @@ namespace Avalonia.Controls.UnitTests
Assert.Equal(1, panel.VisualChildren.Count);
}
- [Fact]
- public void Alternating_Backgrounds_Should_Be_Correct_After_Scrolling()
+ [Theory]
+ [InlineData(0d, 0, 8, 1,9)]
+ [InlineData(0.5d, 0, 17, 0, 17)]
+ public void Alternating_Backgrounds_Should_Be_Correct_After_Scrolling(double bufferFactor,
+ int firstIndex1,
+ int lastIndex1,
+ int firstIndex2,
+ int lastIndex2)
{
// Issue #12381.
static void AssertColors(VirtualizingStackPanel target)
@@ -1059,7 +1189,7 @@ namespace Avalonia.Controls.UnitTests
Setters = { new Setter(ListBoxItem.BackgroundProperty, Brushes.Red) },
},
};
- var (target, scroll, itemsControl) = CreateUnrootedTarget();
+ var (target, scroll, itemsControl) = CreateUnrootedTarget(bufferFactor: bufferFactor);
// We need to display an odd number of items to reproduce the issue.
var root = CreateRoot(itemsControl, clientSize: new(100, 90), styles: styles);
@@ -1069,47 +1199,51 @@ namespace Avalonia.Controls.UnitTests
.Cast()
.ToList();
- Assert.Equal(0, target.FirstRealizedIndex);
- Assert.Equal(8, target.LastRealizedIndex);
+ Assert.Equal(firstIndex1, target.FirstRealizedIndex);
+ Assert.Equal(lastIndex1, target.LastRealizedIndex);
AssertColors(target);
scroll.Offset = new Vector(0, 10);
target.UpdateLayout();
- Assert.Equal(1, target.FirstRealizedIndex);
- Assert.Equal(9, target.LastRealizedIndex);
+ Assert.Equal(firstIndex2, target.FirstRealizedIndex);
+ Assert.Equal(lastIndex2, target.LastRealizedIndex);
AssertColors(target);
}
- [Fact]
- public void Inserting_Item_Before_Viewport_Preserves_FirstRealizedIndex()
+ [Theory]
+ [InlineData(0d, 20)]
+ [InlineData(0.5d, 15)]
+ public void Inserting_Item_Before_Viewport_Preserves_FirstRealizedIndex(double bufferFactor, int firstIndex)
{
// Issue #12744
using var app = App();
- var (target, scroll, itemsControl) = CreateTarget();
+ var (target, scroll, itemsControl) = CreateTarget(bufferFactor: bufferFactor);
var items = (IList)itemsControl.ItemsSource!;
// Scroll down 20 items.
scroll.Offset = new Vector(0, 200);
target.UpdateLayout();
- Assert.Equal(20, target.FirstRealizedIndex);
+ Assert.Equal(firstIndex, target.FirstRealizedIndex);
// Insert an item at the beginning.
items.Insert(0, "New Item");
target.UpdateLayout();
// The first realized index should still be 20 as the scroll should be unchanged.
- Assert.Equal(20, target.FirstRealizedIndex);
+ Assert.Equal(firstIndex, target.FirstRealizedIndex);
Assert.Equal(new(0, 200), scroll.Offset);
}
- [Fact]
- public void Can_Bind_Item_IsVisible()
+ [Theory]
+ [InlineData(0d)]
+ [InlineData(0.5d)]
+ public void Can_Bind_Item_IsVisible(double bufferFactor)
{
using var app = App();
var style = CreateIsVisibleBindingStyle();
var items = Enumerable.Range(0, 100).Select(x => new ItemWithIsVisible(x)).ToList();
- var (target, scroll, itemsControl) = CreateTarget(items: items, styles: new[] { style });
+ var (target, scroll, itemsControl) = CreateTarget(items: items, styles: new[] { style }, bufferFactor: bufferFactor);
var container = target.ContainerFromIndex(2)!;
Assert.True(container.IsVisible);
@@ -1124,13 +1258,15 @@ namespace Avalonia.Controls.UnitTests
Assert.Equal(20, target.ContainerFromIndex(3)!.Bounds.Top);
}
- [Fact]
- public void IsVisible_Binding_Persists_After_Scrolling()
+ [Theory]
+ [InlineData(0d)]
+ [InlineData(0.5d)]
+ public void IsVisible_Binding_Persists_After_Scrolling(double bufferFactor)
{
using var app = App();
var style = CreateIsVisibleBindingStyle();
var items = Enumerable.Range(0, 100).Select(x => new ItemWithIsVisible(x)).ToList();
- var (target, scroll, itemsControl) = CreateTarget(items: items, styles: new[] { style });
+ var (target, scroll, itemsControl) = CreateTarget(items: items, styles: new[] { style }, bufferFactor: bufferFactor);
var container = target.ContainerFromIndex(2)!;
Assert.True(container.IsVisible);
@@ -1147,13 +1283,16 @@ namespace Avalonia.Controls.UnitTests
Assert.False(container.IsVisible);
}
- [Fact]
- public void Recycling_A_Hidden_Control_Shows_It()
+ [Theory]
+ [InlineData(0d)]
+ [InlineData(0.5d)]
+ public void Recycling_A_Hidden_Control_Shows_It(double bufferFactor)
{
using var app = App();
var style = CreateIsVisibleBindingStyle();
- var items = Enumerable.Range(0, 3).Select(x => new ItemWithIsVisible(x)).ToList();
- var (target, scroll, itemsControl) = CreateTarget(items: items, styles: new[] { style });
+ var itemsList = Enumerable.Range(0, 3).Select(x => new ItemWithIsVisible(x)).ToList();
+ var items = new ObservableCollection(itemsList);
+ var (target, scroll, itemsControl) = CreateTarget(items: items, styles: new[] { style }, bufferFactor: bufferFactor);
var container = target.ContainerFromIndex(2)!;
Assert.True(container.IsVisible);
@@ -1171,8 +1310,10 @@ namespace Avalonia.Controls.UnitTests
Assert.True(container.IsVisible);
}
- [Fact]
- public void ScrollIntoView_With_TargetRect_Outside_Viewport_Should_Scroll_To_Item()
+ [Theory]
+ [InlineData(0d)]
+ [InlineData(0.5d)]
+ public void ScrollIntoView_With_TargetRect_Outside_Viewport_Should_Scroll_To_Item(double bufferFactor)
{
using var app = App();
var items = Enumerable.Range(0, 101).Select(x => new ItemWithHeight(x, x * 100 + 1));
@@ -1194,7 +1335,8 @@ namespace Avalonia.Controls.UnitTests
new Setter(ScrollViewer.HorizontalScrollBarVisibilityProperty, ScrollBarVisibility.Visible),
}
}
- });
+ },
+ bufferFactor: bufferFactor);
itemsControl.ContainerPrepared += (_, ev) =>
{
ev.Container.AddHandler(Control.RequestBringIntoViewEvent, (_, e) =>
@@ -1209,14 +1351,16 @@ namespace Avalonia.Controls.UnitTests
Assert.Equal(9901, scroll.Offset.X);
}
- [Fact]
- public void ScrollIntoView_Correctly_Scrolls_Down_To_A_Page_Of_Smaller_Items()
+ [Theory]
+ [InlineData(0d, 10, 10)]
+ [InlineData(0.5d, 5, 15)]
+ public void ScrollIntoView_Correctly_Scrolls_Down_To_A_Page_Of_Smaller_Items(double bufferFactor, int firstIndex, int count)
{
using var app = App();
// First 10 items have height of 20, next 10 have height of 10.
var items = Enumerable.Range(0, 20).Select(x => new ItemWithHeight(x, ((29 - x) / 10) * 10));
- var (target, scroll, itemsControl) = CreateTarget(items: items, itemTemplate: CanvasWithHeightTemplate);
+ var (target, scroll, itemsControl) = CreateTarget(items: items, itemTemplate: CanvasWithHeightTemplate, bufferFactor: bufferFactor);
// Scroll the last item into view.
target.ScrollIntoView(19);
@@ -1232,17 +1376,19 @@ namespace Avalonia.Controls.UnitTests
Assert.Equal(new Vector(0, 290), scroll.Offset);
// Items 10-19 should be visible.
- AssertRealizedItems(target, itemsControl, 10, 10);
+ AssertRealizedItems(target, itemsControl, firstIndex, count);
}
- [Fact]
- public void ScrollIntoView_Correctly_Scrolls_Down_To_A_Page_Of_Larger_Items()
+ [Theory]
+ [InlineData(0d, 15, 5, 190, 210, 110)]
+ [InlineData(0.5d, 10, 10, 253, 273, 173)]
+ public void ScrollIntoView_Correctly_Scrolls_Down_To_A_Page_Of_Larger_Items(double bufferFactor, int firstIndex, int count, int y, int extentHeight, int offset)
{
using var app = App();
// First 10 items have height of 10, next 10 have height of 20.
var items = Enumerable.Range(0, 20).Select(x => new ItemWithHeight(x, ((x / 10) + 1) * 10));
- var (target, scroll, itemsControl) = CreateTarget(items: items, itemTemplate: CanvasWithHeightTemplate);
+ var (target, scroll, itemsControl) = CreateTarget(items: items, itemTemplate: CanvasWithHeightTemplate, bufferFactor: bufferFactor);
// Scroll the last item into view.
target.ScrollIntoView(19);
@@ -1252,23 +1398,28 @@ namespace Avalonia.Controls.UnitTests
// accommodate the item height of 20. This is obviously not a perfect answer, but
// it's the best we can do without knowing the actual item heights.
var container = Assert.IsType(target.ContainerFromIndex(19));
- Assert.Equal(new Rect(0, 190, 100, 20), container.Bounds);
+ Assert.Equal(new Rect(0, y, 100, 20), container.Bounds);
Assert.Equal(new Size(100, 100), scroll.Viewport);
- Assert.Equal(new Size(100, 210), scroll.Extent);
- Assert.Equal(new Vector(0, 110), scroll.Offset);
+ Assert.Equal(new Size(100, extentHeight), scroll.Extent);
+ Assert.Equal(new Vector(0, offset), scroll.Offset);
// Items 15-19 should be visible.
- AssertRealizedItems(target, itemsControl, 15, 5);
+ AssertRealizedItems(target, itemsControl, firstIndex, count);
}
- [Fact]
- public void ScrollIntoView_Correctly_Scrolls_Right_To_A_Page_Of_Smaller_Items()
+ [Theory]
+ [InlineData(0d, 10,10)]
+ [InlineData(0.5d, 5, 15)]
+ public void ScrollIntoView_Correctly_Scrolls_Right_To_A_Page_Of_Smaller_Items(double bufferFactor, int firstIndex, int count)
{
using var app = App();
// First 10 items have width of 20, next 10 have width of 10.
var items = Enumerable.Range(0, 20).Select(x => new ItemWithWidth(x, ((29 - x) / 10) * 10));
- var (target, scroll, itemsControl) = CreateTarget(items: items, itemTemplate: CanvasWithWidthTemplate, orientation: Orientation.Horizontal);
+ var (target, scroll, itemsControl) = CreateTarget(items: items,
+ itemTemplate: CanvasWithWidthTemplate,
+ orientation: Orientation.Horizontal,
+ bufferFactor: bufferFactor);
// Scroll the last item into view.
target.ScrollIntoView(19);
@@ -1284,17 +1435,22 @@ namespace Avalonia.Controls.UnitTests
Assert.Equal(new Vector(290, 0), scroll.Offset);
// Items 10-19 should be visible.
- AssertRealizedItems(target, itemsControl, 10, 10);
+ AssertRealizedItems(target, itemsControl, firstIndex, count);
}
- [Fact]
- public void ScrollIntoView_Correctly_Scrolls_Right_To_A_Page_Of_Larger_Items()
+ [Theory]
+ [InlineData(0d, 15, 5, 190, 210, 110)]
+ [InlineData(0.5d, 10, 10, 253, 273, 173)]
+ public void ScrollIntoView_Correctly_Scrolls_Right_To_A_Page_Of_Larger_Items(double bufferFactor, int firstIndex, int count, int x, int extentWidth, int offset)
{
using var app = App();
// First 10 items have width of 10, next 10 have width of 20.
var items = Enumerable.Range(0, 20).Select(x => new ItemWithWidth(x, ((x / 10) + 1) * 10));
- var (target, scroll, itemsControl) = CreateTarget(items: items, itemTemplate: CanvasWithWidthTemplate, orientation: Orientation.Horizontal);
+ var (target, scroll, itemsControl) = CreateTarget(items: items,
+ itemTemplate: CanvasWithWidthTemplate,
+ orientation: Orientation.Horizontal,
+ bufferFactor: bufferFactor);
// Scroll the last item into view.
target.ScrollIntoView(19);
@@ -1304,28 +1460,36 @@ namespace Avalonia.Controls.UnitTests
// accommodate the item width of 20. This is obviously not a perfect answer, but
// it's the best we can do without knowing the actual item widths.
var container = Assert.IsType(target.ContainerFromIndex(19));
- Assert.Equal(new Rect(190, 0, 20, 100), container.Bounds);
+ Assert.Equal(new Rect(x, 0, 20, 100), container.Bounds);
Assert.Equal(new Size(100, 100), scroll.Viewport);
- Assert.Equal(new Size(210, 100), scroll.Extent);
- Assert.Equal(new Vector(110, 0), scroll.Offset);
+ Assert.Equal(new Size(extentWidth, 100), scroll.Extent);
+ Assert.Equal(new Vector(offset, 0), scroll.Offset);
// Items 15-19 should be visible.
- AssertRealizedItems(target, itemsControl, 15, 5);
+ AssertRealizedItems(target, itemsControl, firstIndex, count);
}
- [Fact]
- public void Extent_And_Offset_Should_Be_Updated_When_Containers_Resize()
+ [Theory]
+ [InlineData(0d,
+ 4,5,
+ 8, 11)]
+ [InlineData(0.5d,
+ 3,6,
+ 6, 13)]
+ public void Extent_And_Offset_Should_Be_Updated_When_Containers_Resize(double bufferFactor,
+ int firstIndex1, int lastIndex1,
+ int firstIndex2, int lastIndex2)
{
using var app = App();
// All containers start off with a height of 50 (2 containers fit in viewport).
var items = Enumerable.Range(0, 20).Select(x => new ItemWithHeight(x, 50)).ToList();
- var (target, scroll, itemsControl) = CreateTarget(items: items, itemTemplate: CanvasWithHeightTemplate);
+ var (target, scroll, itemsControl) = CreateTarget(items: items, itemTemplate: CanvasWithHeightTemplate, bufferFactor: bufferFactor);
// Scroll to the 5th item (containers 4 and 5 should be visible).
target.ScrollIntoView(5);
- Assert.Equal(4, target.FirstRealizedIndex);
- Assert.Equal(5, target.LastRealizedIndex);
+ Assert.Equal(firstIndex1, target.FirstRealizedIndex);
+ Assert.Equal(lastIndex1, target.LastRealizedIndex);
// The extent should be 500 (10 * 50) and the offset should be 200 (4 * 50).
var container = Assert.IsType(target.ContainerFromIndex(5));
@@ -1344,23 +1508,31 @@ namespace Avalonia.Controls.UnitTests
Assert.Equal(new Size(100, 100), scroll.Viewport);
Assert.Equal(new Size(100, 500), scroll.Extent);
Assert.Equal(new Vector(0, 200), scroll.Offset);
- Assert.Equal(8, target.FirstRealizedIndex);
- Assert.Equal(11, target.LastRealizedIndex);
+ Assert.Equal(firstIndex2, target.FirstRealizedIndex);
+ Assert.Equal(lastIndex2, target.LastRealizedIndex);
}
- [Fact]
- public void Focused_Container_Is_Positioned_Correctly_when_Container_Size_Change_Causes_It_To_Be_Moved_Out_Of_Visible_Viewport()
+ [Theory]
+ [InlineData(0d,
+ 4, 5,
+ 8, 11)]
+ [InlineData(0.5d,
+ 3, 6,
+ 6, 13)]
+ public void Focused_Container_Is_Positioned_Correctly_when_Container_Size_Change_Causes_It_To_Be_Moved_Out_Of_Visible_Viewport(double bufferFactor,
+ int firstIndex1, int lastIndex1,
+ int firstIndex2, int lastIndex2)
{
using var app = App();
// All containers start off with a height of 50 (2 containers fit in viewport).
var items = Enumerable.Range(0, 20).Select(x => new ItemWithHeight(x, 50)).ToList();
- var (target, scroll, itemsControl) = CreateTarget(items: items, itemTemplate: CanvasWithHeightTemplate);
+ var (target, scroll, itemsControl) = CreateTarget(items: items, itemTemplate: CanvasWithHeightTemplate, bufferFactor: bufferFactor);
// Scroll to the 5th item (containers 4 and 5 should be visible).
target.ScrollIntoView(5);
- Assert.Equal(4, target.FirstRealizedIndex);
- Assert.Equal(5, target.LastRealizedIndex);
+ Assert.Equal(firstIndex1, target.FirstRealizedIndex);
+ Assert.Equal(lastIndex1, target.LastRealizedIndex);
// Focus the 5th item.
var container = Assert.IsType(target.ContainerFromIndex(5));
@@ -1373,27 +1545,38 @@ namespace Avalonia.Controls.UnitTests
target.UpdateLayout();
// The focused container should now be outside the realized range.
- Assert.Equal(8, target.FirstRealizedIndex);
- Assert.Equal(11, target.LastRealizedIndex);
+ Assert.Equal(firstIndex2, target.FirstRealizedIndex);
+ Assert.Equal(lastIndex2, target.LastRealizedIndex);
// The container should still exist and be positioned outside the visible viewport.
container = Assert.IsType(target.ContainerFromIndex(5));
Assert.Equal(new Rect(0, 125, 100, 25), container.Bounds);
}
- [Fact]
- public void Focused_Container_Is_Positioned_Correctly_when_Container_Size_Change_Causes_It_To_Be_Moved_Into_Visible_Viewport()
+ [Theory]
+ [InlineData(0d,
+ 4, 7,
+ 3, 6,
+ 3, 7)]
+ [InlineData(0.5d,
+ 0, 7,
+ 0, 7,
+ 0, 9)]
+ public void Focused_Container_Is_Positioned_Correctly_when_Container_Size_Change_Causes_It_To_Be_Moved_Into_Visible_Viewport(double bufferFactor,
+ int firstIndex1, int lastIndex1,
+ int firstIndex2, int lastIndex2,
+ int firstIndex3, int lastIndex3)
{
using var app = App();
// All containers start off with a height of 25 (4 containers fit in viewport).
var items = Enumerable.Range(0, 20).Select(x => new ItemWithHeight(x, 25)).ToList();
- var (target, scroll, itemsControl) = CreateTarget(items: items, itemTemplate: CanvasWithHeightTemplate);
+ var (target, scroll, itemsControl) = CreateTarget(items: items, itemTemplate: CanvasWithHeightTemplate, bufferFactor: bufferFactor);
// Scroll to the 5th item (containers 4-7 should be visible).
target.ScrollIntoView(7);
- Assert.Equal(4, target.FirstRealizedIndex);
- Assert.Equal(7, target.LastRealizedIndex);
+ Assert.Equal(firstIndex1, target.FirstRealizedIndex);
+ Assert.Equal(lastIndex1, target.LastRealizedIndex);
// Focus the 7th item.
var container = Assert.IsType(target.ContainerFromIndex(7));
@@ -1402,8 +1585,8 @@ namespace Avalonia.Controls.UnitTests
// Scroll up to the 3rd item (containers 3-6 should still be visible).
target.ScrollIntoView(3);
- Assert.Equal(3, target.FirstRealizedIndex);
- Assert.Equal(6, target.LastRealizedIndex);
+ Assert.Equal(firstIndex2, target.FirstRealizedIndex);
+ Assert.Equal(lastIndex2, target.LastRealizedIndex);
// Update the height of all items to 20 and run a layout pass.
foreach (var item in items)
@@ -1411,14 +1594,598 @@ namespace Avalonia.Controls.UnitTests
target.UpdateLayout();
// The focused container should now be inside the realized range.
- Assert.Equal(3, target.FirstRealizedIndex);
- Assert.Equal(7, target.LastRealizedIndex);
+ Assert.Equal(firstIndex3, target.FirstRealizedIndex);
+ Assert.Equal(lastIndex3, target.LastRealizedIndex);
// The container should be positioned correctly.
container = Assert.IsType(target.ContainerFromIndex(7));
Assert.Equal(new Rect(0, 140, 100, 20), container.Bounds);
}
+ [Fact]
+ public void When_Vertical_Calculates_ViewPort_At_Start_Of_List()
+ {
+ // Arrange
+ using var app = App();
+
+ var items = Enumerable.Range(0, 100).Select(x => new ItemWithHeight(x)).ToList();
+
+ // Act
+ var (target, scroll, itemsControl) =
+ CreateTarget(
+ items: items,
+ itemTemplate: CanvasWithHeightTemplate,
+ bufferFactor:0.5d);
+
+ // Assert
+ Assert.Equal(0, target.ViewPort.Top);
+ Assert.Equal(100, target.ViewPort.Bottom);
+
+ Assert.Equal(0, target.ExtendedViewPort.Top);
+ Assert.Equal(200, target.ExtendedViewPort.Bottom);
+ }
+
+ [Fact]
+ public void When_Vertical_Calculates_ViewPort_At_End_Of_List()
+ {
+ // Arrange
+ using var app = App();
+
+ var items = Enumerable.Range(0, 100).Select(x => new ItemWithHeight(x)).ToList();
+ var (target, scroll, itemsControl) =
+ CreateTarget(
+ items: items,
+ itemTemplate: CanvasWithHeightTemplate,
+ bufferFactor: 0.5d);
+
+ // Act
+ scroll.Offset = new Vector(0, 910); // scroll to end
+ Layout(target);
+
+ // Assert
+ Assert.Equal(900, target.ViewPort.Top);
+ Assert.Equal(1000, target.ViewPort.Bottom);
+
+ Assert.Equal(800, target.ExtendedViewPort.Top);
+ Assert.Equal(1000, target.ExtendedViewPort.Bottom);
+ }
+
+ [Fact]
+ public void When_Vertical_Calculates_ViewPort_In_Middle_Of_List()
+ {
+ // Arrange
+ using var app = App();
+
+ var items = Enumerable.Range(0, 100).Select(x => new ItemWithHeight(x)).ToList();
+ var (target, scroll, itemsControl) =
+ CreateTarget(
+ items: items,
+ itemTemplate: CanvasWithHeightTemplate,
+ bufferFactor: 0.5d);
+
+ // Act
+ scroll.Offset = new Vector(0, 500); // scroll to end
+ Layout(target);
+
+ // Assert
+ Assert.Equal(500, target.ViewPort.Top);
+ Assert.Equal(600, target.ViewPort.Bottom);
+
+ Assert.Equal(450, target.ExtendedViewPort.Top);
+ Assert.Equal(650, target.ExtendedViewPort.Bottom);
+ }
+
+ [Fact]
+ public void When_Horizontal_Calculates_ViewPort_At_Start_Of_List()
+ {
+ // Arrange
+ using var app = App();
+
+ var items = Enumerable.Range(0, 100).Select(x => new ItemWithWidth(x)).ToList();
+
+ // Act
+ var (target, scroll, itemsControl) =
+ CreateTarget(
+ items: items,
+ itemTemplate: CanvasWithWidthTemplate,
+ orientation: Orientation.Horizontal,
+ bufferFactor: 0.5d);
+
+ // Assert
+ Assert.Equal(0, target.ViewPort.Left);
+ Assert.Equal(100, target.ViewPort.Right);
+
+ Assert.Equal(0, target.ExtendedViewPort.Left);
+ Assert.Equal(200, target.ExtendedViewPort.Right);
+ }
+
+ [Fact]
+ public void When_Horizontal_Calculates_ViewPort_At_End_Of_List()
+ {
+ // Arrange
+ using var app = App();
+
+ var items = Enumerable.Range(0, 100).Select(x => new ItemWithWidth(x)).ToList();
+ var (target, scroll, itemsControl) =
+ CreateTarget(
+ items: items,
+ itemTemplate: CanvasWithWidthTemplate,
+ orientation: Orientation.Horizontal,
+ bufferFactor: 0.5d);
+ // Act
+ scroll.Offset = new Vector(900, 0); // scroll to end
+ Layout(target);
+
+ // Assert
+ Assert.Equal(900, target.ViewPort.Left);
+ Assert.Equal(1000, target.ViewPort.Right);
+
+ Assert.Equal(800, target.ExtendedViewPort.Left);
+ Assert.Equal(1000, target.ExtendedViewPort.Right);
+ }
+
+ [Fact]
+ public void When_Horizontal_Calculates_ViewPort_In_Middle_Of_List()
+ {
+ // Arrange
+ using var app = App();
+
+ var items = Enumerable.Range(0, 100).Select(x => new ItemWithWidth(x)).ToList();
+ var (target, scroll, itemsControl) =
+ CreateTarget(
+ items: items,
+ itemTemplate: CanvasWithWidthTemplate,
+ orientation: Orientation.Horizontal,
+ bufferFactor: 0.5d);
+
+ // Act
+ scroll.Offset = new Vector(500, 0); // scroll to end
+ Layout(target);
+
+ // Assert
+ Assert.Equal(500, target.ViewPort.Left);
+ Assert.Equal(600, target.ViewPort.Right);
+
+ Assert.Equal(450, target.ExtendedViewPort.Left);
+ Assert.Equal(650, target.ExtendedViewPort.Right);
+ }
+
+ [Fact]
+ public void Scrolling_Down_Does_Not_Measure_Or_Arrange_Until_Extended_ViewPort_Bounds_Are_Reached()
+ {
+ using var app = App();
+
+ var items = Enumerable.Range(0, 100).Select(x => new ItemWithHeightAndMeasureArrangeCount(x)).ToList();
+
+ var (target, scroll, itemsControl) =
+ CreateTarget(
+ items: items,
+ itemTemplate: CanvasWithHeightTemplate,
+ bufferFactor: 0.5d);
+
+ Assert.True(target.LastRealizedIndex == 19,
+ $"Should show 20 items but last realized index was {target.LastRealizedIndex}");
+
+ // reset counters
+ target.ResetMeasureArrangeCounters();
+ // shows 20 items, each is 10 high.
+ // visible are 10 => need to scroll down 100px until the next 5 (visible*BufferFactor) additional items are added.
+ // until then no measure-arrange call should happen
+
+ // Scroll down until the extended viewport bounds are reached
+ while (target.LastRealizedIndex < 20)
+ {
+ scroll.Offset = new Vector(0, scroll.Offset.Y + 5);
+ Layout(target);
+ }
+
+ // Assert
+ Assert.True(target.Measured == 1, "should be measured only once");
+ Assert.True(target.Arranged == 1, "should be arranged only once");
+
+ // the first 5 additional items will be reused when scrolling down, but the remaining 10 visible + 5 additional not touched at all
+ var expectedUntouchedItems =
+ items.Skip(5 /*additional items*/).Take(15).ToList();
+ foreach (var itm in expectedUntouchedItems)
+ {
+ Assert.True(itm.Measured == 0, $"{itm.Caption} should not be measured but was {itm.Measured} times");
+ Assert.True(itm.Arranged == 0, $"{itm.Caption} should not be arranged but was {itm.Arranged} times");
+ }
+
+ var newAdditionalItems = items.Skip(20).Take(5);
+ foreach (var itm in newAdditionalItems)
+ {
+ Assert.True(itm.Measured == 1, $"{itm.Caption} should be measured but was {itm.Measured} times");
+ Assert.True(itm.Arranged == 1, $"{itm.Caption} should be measured but was {itm.Arranged} times");
+ }
+ }
+
+ [Fact]
+ public void Scrolling_Up_Does_Not_Measure_Or_Arrange_Until_Extended_ViewPort_Bounds_Are_Reached()
+ {
+ using var app = App();
+
+ var items = Enumerable.Range(0, 100).Select(x => new ItemWithHeightAndMeasureArrangeCount(x)).ToList();
+
+ var (target, scroll, itemsControl) =
+ CreateTarget(
+ items: items,
+ itemTemplate: CanvasWithHeightTemplate,
+ bufferFactor: 0.5d);
+
+ // scroll a bit down so we are not near the start of the list
+ scroll.Offset = new Vector(0, 200);
+ Layout(target);
+
+ Assert.True(target.FirstRealizedIndex == 15,
+ $"Should show items from 20 to 30 (so 15 to 35 including additional items) but first realized index was {target.FirstRealizedIndex}");
+
+ // reset counters
+ target.ResetMeasureArrangeCounters();
+ // shows 20 items, each is 10 high.
+ // visible are 10 => need to scroll down 100px until the next 5 (visible*BufferFactor) additional items are added.
+ // until then no measure-arrange call should happen
+
+ var initialFirstRealizedIndex = target.FirstRealizedIndex;
+
+ // Scroll down until the extended viewport bounds are reached
+ while (target.FirstRealizedIndex >= 15)
+ {
+ scroll.Offset = new Vector(0, scroll.Offset.Y - 5);
+ Layout(target);
+ }
+
+ // Assert
+ Assert.True(target.Measured == 1, "should be measured only once");
+ Assert.True(target.Arranged == 1, "should be arranged only once");
+
+ // the last 5 additional items will be reused when scrolling up, but the remaining 10 visible + 5 additional not touched at all
+ var expectedUntouchedItems = items.Skip(initialFirstRealizedIndex + 1).Take(15).ToList();
+ foreach (var itm in expectedUntouchedItems)
+ {
+ Assert.True(itm.Measured == 0, $"{itm.Caption} should not be measured but was {itm.Measured} times");
+ Assert.True(itm.Arranged == 0, $"{itm.Caption} should not be arranged but was {itm.Arranged} times");
+ }
+
+ // now that we scrolled up to index 19, items 18,17,16,15 and 14 should be the "additional" ones
+ var newAdditionalItems = items.Skip(initialFirstRealizedIndex - 6).Take(6);
+ foreach (var itm in newAdditionalItems)
+ {
+ Assert.True(itm.Measured == 1, $"{itm.Caption} should be measured but was {itm.Measured} times");
+ Assert.True(itm.Arranged == 1, $"{itm.Caption} should be measured but was {itm.Arranged} times");
+ }
+ }
+
+ [Fact]
+ public void Scrolling_Down_To_End_Of_List_Only_Measures_Once_When_Last_Item_Is_Reached()
+ {
+ using var app = App();
+
+ var items = Enumerable.Range(0, 100).Select(x => new ItemWithHeightAndMeasureArrangeCount(x)).ToList();
+
+ var (target, scroll, itemsControl) =
+ CreateTarget(
+ items: items,
+ itemTemplate: CanvasWithHeightTemplate,
+ bufferFactor: 0.5d);
+
+ // scroll a bit down so we are near the end of the list
+ scroll.Offset = new Vector(0, 800); // so we render 75 to 95 with a buffer size of 5
+ Layout(target);
+
+ Assert.True(target.LastRealizedIndex == 94,
+ $"Should show 20 items but last realized index was {target.LastRealizedIndex}");
+
+ // reset counters
+ target.ResetMeasureArrangeCounters();
+ // shows 20 items, each is 10 high.
+ // visible are 10 => need to scroll down 100px until the next 5 (visible*BufferFactor) additional items are added.
+ // until then no measure-arrange call should happen
+
+ var initialLastRealizedIndex = target.LastRealizedIndex;
+
+ // Scroll down until we reached the very last item
+ while (target.LastRealizedIndex < 99)
+ {
+ scroll.Offset = new Vector(0, scroll.Offset.Y + 5);
+ Layout(target);
+ }
+
+ // Assert
+ Assert.True(target.Measured == 1, "should be measured only once even though we are at the end of the list");
+ Assert.True(target.Arranged == 1, "should be arranged only once even though we are at the end of the list");
+
+ // the first 5 additional items will be reused when scrolling down, but the remaining 10 visible + 5 additional not touched at all
+ var expectedUntouchedItems =
+ items.Skip(initialLastRealizedIndex + 1 - 15).Take(15).ToList();
+ foreach (var itm in expectedUntouchedItems)
+ {
+ Assert.True(itm.Measured == 0, $"{itm.Caption} should not be measured but was {itm.Measured} times");
+ Assert.True(itm.Arranged == 0, $"{itm.Caption} should not be arranged but was {itm.Arranged} times");
+ }
+
+ var newAdditionalItems = items.Skip(initialLastRealizedIndex + 1).Take(5);
+ foreach (var itm in newAdditionalItems)
+ {
+ Assert.True(itm.Measured == 1, $"{itm.Caption} should be measured but was {itm.Measured} times");
+ Assert.True(itm.Arranged == 1, $"{itm.Caption} should be measured but was {itm.Arranged} times");
+ }
+ }
+
+ [Fact]
+ public void Scrolling_Up_To_Start_Of_List_Only_Measures_Once_When_First_Item_Is_Reached()
+ {
+ using var app = App();
+
+ var items = Enumerable.Range(0, 100).Select(x => new ItemWithHeightAndMeasureArrangeCount(x)).ToList();
+
+ var (target, scroll, itemsControl) =
+ CreateTarget(
+ items: items,
+ itemTemplate: CanvasWithHeightTemplate,
+ bufferFactor: 0.5d);
+
+ // scroll a bit down so we are not near the start of the list
+ scroll.Offset = new Vector(0, 105);
+ Layout(target);
+
+ Assert.True(target.FirstRealizedIndex == 5,
+ $"Should show items from 10 to 20 (so 5 to 25 including additional items) but first realized index was {target.FirstRealizedIndex}");
+
+ // reset counters
+ target.ResetMeasureArrangeCounters();
+ // shows 20 items, each is 10 high.
+ // visible are 10 => need to scroll down 100px until the next 5 (visible*BufferFactor) additional items are added.
+ // until then no measure-arrange call should happen
+
+ // Scroll down until the extended viewport bounds are reached
+ while (target.FirstRealizedIndex > 0)
+ {
+ scroll.Offset = new Vector(0, scroll.Offset.Y - 5);
+ Layout(target);
+ }
+
+ // Assert
+ Assert.True(target.Measured == 1, "should be measured only once even though we are at the start of the list");
+ Assert.True(target.Arranged == 1, "should be arranged only once even though we are at the start of the list");
+
+ // the last 5 additional items will be reused when scrolling up, but the remaining 10 visible + 5 additional not touched at all
+ var expectedMeasuredItems = items.Take(20).ToList();
+ foreach (var itm in expectedMeasuredItems)
+ {
+ Assert.True(itm.Measured == 1, $"{itm.Caption} should be measured but was {itm.Measured} times");
+ Assert.True(itm.Arranged == 1, $"{itm.Caption} should be arranged but was {itm.Arranged} times");
+ }
+
+ // now that we scrolled up to index 19, items 18,17,16,15 and 14 should be the "additional" ones
+ var untouchedItems = items.Skip(20).ToList();
+ foreach (var itm in untouchedItems)
+ {
+ Assert.True(itm.Measured == 0, $"{itm.Caption} should not be measured but was {itm.Measured} times");
+ Assert.True(itm.Arranged == 0, $"{itm.Caption} should not be measured but was {itm.Arranged} times");
+ }
+ }
+
+ [Fact]
+ public void Scrolling_Right_Does_Not_Measure_Or_Arrange_Until_Extended_ViewPort_Bounds_Are_Reached()
+ {
+ using var app = App();
+
+ var items = Enumerable.Range(0, 100).Select(x => new ItemWithWidthAndMeasureArrangeCount(x)).ToList();
+
+ var (target, scroll, itemsControl) =
+ CreateTarget(
+ items: items,
+ itemTemplate: CanvasWithWidthTemplate,
+ orientation: Orientation.Horizontal,
+ bufferFactor: 0.5d);
+
+ Assert.True(target.LastRealizedIndex == 19,
+ $"Should show 20 items but last realized index was {target.LastRealizedIndex}");
+
+ // reset counters
+ target.ResetMeasureArrangeCounters();
+ // shows 20 items, each is 10 high.
+ // visible are 10 => need to scroll down 100px until the next 5 (visible*BufferFactor) additional items are added.
+ // until then no measure-arrange call should happen
+
+ // Scroll down until the extended viewport bounds are reached
+ while (target.LastRealizedIndex < 20)
+ {
+ scroll.Offset = new Vector(scroll.Offset.X + 5, 0);
+ Layout(target);
+ }
+
+ // Assert
+ Assert.True(target.Measured == 1, "should be measured only once");
+ Assert.True(target.Arranged == 1, "should be arranged only once");
+
+ // the first 5 additional items will be reused when scrolling down, but the remaining 10 visible + 5 additional not touched at all
+ var expectedUntouchedItems =
+ items.Skip(5 /*additional items*/).Take(15).ToList();
+ foreach (var itm in expectedUntouchedItems)
+ {
+ Assert.True(itm.Measured == 0, $"{itm.Caption} should not be measured but was {itm.Measured} times");
+ Assert.True(itm.Arranged == 0, $"{itm.Caption} should not be arranged but was {itm.Arranged} times");
+ }
+
+ var newAdditionalItems = items.Skip(20).Take(5);
+ foreach (var itm in newAdditionalItems)
+ {
+ Assert.True(itm.Measured == 1, $"{itm.Caption} should be measured but was {itm.Measured} times");
+ Assert.True(itm.Arranged == 1, $"{itm.Caption} should be measured but was {itm.Arranged} times");
+ }
+ }
+
+ [Fact]
+ public void Scrolling_Left_Does_Not_Measure_Or_Arrange_Until_Extended_ViewPort_Bounds_Are_Reached()
+ {
+ using var app = App();
+
+ var items = Enumerable.Range(0, 100).Select(x => new ItemWithWidthAndMeasureArrangeCount(x)).ToList();
+
+ var (target, scroll, itemsControl) =
+ CreateTarget(
+ items: items,
+ itemTemplate: CanvasWithWidthTemplate,
+ orientation: Orientation.Horizontal,
+ bufferFactor: 0.5d);
+
+ // scroll a bit down so we are not near the start of the list
+ scroll.Offset = new Vector(200, 0);
+ Layout(target);
+
+ Assert.True(target.FirstRealizedIndex == 15,
+ $"Should show items from 20 to 30 (so 15 to 35 including additional items) but first realized index was {target.FirstRealizedIndex}");
+
+ // reset counters
+ target.ResetMeasureArrangeCounters();
+ // shows 20 items, each is 10 high.
+ // visible are 10 => need to scroll down 100px until the next 5 (visible*BufferFactor) additional items are added.
+ // until then no measure-arrange call should happen
+
+ var initialFirstRealizedIndex = target.FirstRealizedIndex;
+
+ // Scroll down until the extended viewport bounds are reached
+ while (target.FirstRealizedIndex >= 15)
+ {
+ scroll.Offset = new Vector(scroll.Offset.X - 5, 0);
+ Layout(target);
+ }
+
+ // Assert
+ Assert.True(target.Measured == 1, "should be measured only once");
+ Assert.True(target.Arranged == 1, "should be arranged only once");
+
+ // the last 5 additional items will be reused when scrolling up, but the remaining 10 visible + 5 additional not touched at all
+ var expectedUntouchedItems = items.Skip(initialFirstRealizedIndex + 1).Take(15).ToList();
+ foreach (var itm in expectedUntouchedItems)
+ {
+ Assert.True(itm.Measured == 0, $"{itm.Caption} should not be measured but was {itm.Measured} times");
+ Assert.True(itm.Arranged == 0, $"{itm.Caption} should not be arranged but was {itm.Arranged} times");
+ }
+
+ // now that we scrolled up to index 19, items 18,17,16,15 and 14 should be the "additional" ones
+ var newAdditionalItems = items.Skip(initialFirstRealizedIndex - 6).Take(6);
+ foreach (var itm in newAdditionalItems)
+ {
+ Assert.True(itm.Measured == 1, $"{itm.Caption} should be measured but was {itm.Measured} times");
+ Assert.True(itm.Arranged == 1, $"{itm.Caption} should be measured but was {itm.Arranged} times");
+ }
+ }
+
+ [Fact]
+ public void Scrolling_Right_To_End_Of_List_Only_Measures_Once_When_Last_Item_Is_Reached()
+ {
+ using var app = App();
+
+ var items = Enumerable.Range(0, 100).Select(x => new ItemWithWidthAndMeasureArrangeCount(x)).ToList();
+
+ var (target, scroll, itemsControl) =
+ CreateTarget(
+ items: items,
+ itemTemplate: CanvasWithWidthTemplate,
+ orientation: Orientation.Horizontal,
+ bufferFactor: 0.5d);
+
+ // scroll a bit down so we are near the end of the list
+ scroll.Offset = new Vector(800, 0); // so we render 75 to 95 with a buffer size of 5
+ Layout(target);
+
+ Assert.True(target.LastRealizedIndex == 94,
+ $"Should show 20 items but last realized index was {target.LastRealizedIndex}");
+
+ // reset counters
+ target.ResetMeasureArrangeCounters();
+ // shows 20 items, each is 10 high.
+ // visible are 10 => need to scroll down 100px until the next 5 (visible*BufferFactor) additional items are added.
+ // until then no measure-arrange call should happen
+
+ var initialLastRealizedIndex = target.LastRealizedIndex;
+
+ // Scroll down until we reached the very last item
+ while (target.LastRealizedIndex < 99)
+ {
+ scroll.Offset = new Vector(scroll.Offset.X + 5, 0);
+ Layout(target);
+ }
+
+ // Assert
+ Assert.True(target.Measured == 1, "should be measured only once even though we are at the end of the list");
+ Assert.True(target.Arranged == 1, "should be arranged only once even though we are at the end of the list");
+
+ // the first 5 additional items will be reused when scrolling down, but the remaining 10 visible + 5 additional not touched at all
+ var expectedUntouchedItems =
+ items.Skip(initialLastRealizedIndex + 1 - 15).Take(15).ToList();
+ foreach (var itm in expectedUntouchedItems)
+ {
+ Assert.True(itm.Measured == 0, $"{itm.Caption} should not be measured but was {itm.Measured} times");
+ Assert.True(itm.Arranged == 0, $"{itm.Caption} should not be arranged but was {itm.Arranged} times");
+ }
+
+ var newAdditionalItems = items.Skip(initialLastRealizedIndex + 1).Take(5);
+ foreach (var itm in newAdditionalItems)
+ {
+ Assert.True(itm.Measured == 1, $"{itm.Caption} should be measured but was {itm.Measured} times");
+ Assert.True(itm.Arranged == 1, $"{itm.Caption} should be measured but was {itm.Arranged} times");
+ }
+ }
+
+ [Fact]
+ public void Scrolling_Left_To_Start_Of_List_Only_Measures_Once_When_First_Item_Is_Reached()
+ {
+ using var app = App();
+
+ var items = Enumerable.Range(0, 100).Select(x => new ItemWithWidthAndMeasureArrangeCount(x)).ToList();
+
+ var (target, scroll, itemsControl) =
+ CreateTarget(
+ items: items,
+ itemTemplate: CanvasWithWidthTemplate,
+ orientation: Orientation.Horizontal,
+ bufferFactor: 0.5d);
+
+ // scroll a bit down so we are not near the start of the list
+ scroll.Offset = new Vector(105, 0);
+ Layout(target);
+
+ Assert.True(target.FirstRealizedIndex == 5,
+ $"Should show items from 10 to 20 (so 5 to 25 including additional items) but first realized index was {target.FirstRealizedIndex}");
+
+ // reset counters
+ target.ResetMeasureArrangeCounters();
+ // shows 20 items, each is 10 high.
+ // visible are 10 => need to scroll down 100px until the next 5 (visible*BufferFactor) additional items are added.
+ // until then no measure-arrange call should happen
+
+ // Scroll down until the extended viewport bounds are reached
+ while (target.FirstRealizedIndex > 0)
+ {
+ scroll.Offset = new Vector(scroll.Offset.X - 5, 0);
+ Layout(target);
+ }
+
+ // Assert
+ Assert.True(target.Measured == 1, "should be measured only once even though we are at the start of the list");
+ Assert.True(target.Arranged == 1, "should be arranged only once even though we are at the start of the list");
+
+ // the last 5 additional items will be reused when scrolling up, but the remaining 10 visible + 5 additional not touched at all
+ var expectedMeasuredItems = items.Take(20).ToList();
+ foreach (var itm in expectedMeasuredItems)
+ {
+ Assert.True(itm.Measured == 1, $"{itm.Caption} should be measured but was {itm.Measured} times");
+ Assert.True(itm.Arranged == 1, $"{itm.Caption} should be arranged but was {itm.Arranged} times");
+ }
+
+ // now that we scrolled up to index 19, items 18,17,16,15 and 14 should be the "additional" ones
+ var untouchedItems = items.Skip(20).ToList();
+ foreach (var itm in untouchedItems)
+ {
+ Assert.True(itm.Measured == 0, $"{itm.Caption} should not be measured but was {itm.Measured} times");
+ Assert.True(itm.Arranged == 0, $"{itm.Caption} should not be measured but was {itm.Arranged} times");
+ }
+ }
+
private static IReadOnlyList GetRealizedIndexes(VirtualizingStackPanel target, ItemsControl itemsControl)
{
return target.GetRealizedElements()
@@ -1465,28 +2232,33 @@ namespace Avalonia.Controls.UnitTests
.ToList();
Assert.Equal(Enumerable.Range(firstIndex, count), childIndexes);
}
-
private static (VirtualizingStackPanel, ScrollViewer, ItemsControl) CreateTarget(
IEnumerable? items = null,
Optional itemTemplate = default,
IEnumerable