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Avoid unnecessary delegate/closure allocations in UIElementAutomationPeer #10691

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Avoid unnecessary delegate/closure allocations in UIElementAutomationPeer #10691

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1af1a9f
Avoid constant IteratorCallback allocations
h3xds1nz Mar 31, 2025
aa9948a
Add nullability, swap branch for perf
h3xds1nz Apr 1, 2025
80e1f43
Add a comment
h3xds1nz Apr 1, 2025
95de67b
Make the delegate private
h3xds1nz Apr 1, 2025
3d5663b
Share the implementation between 2D and 3D
h3xds1nz Apr 1, 2025
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1 change: 1 addition & 0 deletions src/Microsoft.DotNet.Wpf/src/PresentationCore/PresentationCore.csproj
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Original file line number Diff line number Diff line change
Expand Up @@ -459,6 +459,7 @@
<Compile Include="System\Windows\Automation\Peers\GenericRootAutomationPeer.cs" />
<Compile Include="System\Windows\Automation\Peers\UIElement3DAutomationPeer.cs" />
<Compile Include="System\Windows\Automation\Peers\UIElementAutomationPeer.cs" />
<Compile Include="System\Windows\Automation\Peers\UIElementAutomationUtils.cs" />
<Compile Include="System\Windows\Diagnostics\VisualDiagnostics.cs" />
<Compile Include="System\Windows\Diagnostics\VisualTreeChangeEventArgs.cs" />
<Compile Include="System\Windows\Diagnostics\XamlSourceInfo.cs" />
Expand Down
68 changes: 19 additions & 49 deletions ...Net.Wpf/src/PresentationCore/System/Windows/Automation/Peers/UIElement3DAutomationPeer.cs
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Original file line number Diff line number Diff line change
@@ -1,4 +1,4 @@
// Licensed to the .NET Foundation under one or more agreements.
// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.

using System.Windows.Input;
Expand Down Expand Up @@ -54,61 +54,31 @@ public static AutomationPeer FromElement(UIElement3D element)

return element.GetAutomationPeer();
}

///
override protected List<AutomationPeer> GetChildrenCore()

#nullable enable

/// <summary>
/// Retrieves the automation peers for the <see cref="UIElement"/> / <see cref="UIElement3D"/> children of this <see cref="_owner"/>.
/// </summary>
/// <returns>
/// Returns <see langword="null"/> if the <see cref="_owner"/> has no children of given type, otherwise a list of children.
/// </returns>
protected override List<AutomationPeer>? GetChildrenCore()
{
List<AutomationPeer> children = null;
List<AutomationPeer>? children = null;

iterate(_owner,
(IteratorCallback)delegate(AutomationPeer peer)
{
if (children == null)
children = new List<AutomationPeer>();
UIElementAutomationUtils.Iterate(_owner, ref children, static (ref List<AutomationPeer>? children, AutomationPeer peer) =>
{
children ??= new List<AutomationPeer>();
children.Add(peer);

children.Add(peer);
return (false);
});
return false;
});

return children;
}

private delegate bool IteratorCallback(AutomationPeer peer);

//
private static bool iterate(DependencyObject parent, IteratorCallback callback)
{
bool done = false;

if(parent != null)
{
AutomationPeer peer = null;
int count = VisualTreeHelper.GetChildrenCount(parent);
for (int i = 0; i < count && !done; i++)
{
DependencyObject child = VisualTreeHelper.GetChild(parent, i);

if( child != null
&& child is UIElement
&& (peer = UIElementAutomationPeer.CreatePeerForElement((UIElement)child)) != null )
{
done = callback(peer);
}
else if ( child != null
&& child is UIElement3D
&& (peer = CreatePeerForElement(((UIElement3D)child))) != null )
{
done = callback(peer);
}
else
{
done = iterate(child, callback);
}
}
}

return done;
}
#nullable disable

///
override public object GetPattern(PatternInterface patternInterface)
Expand Down
86 changes: 28 additions & 58 deletions ...otNet.Wpf/src/PresentationCore/System/Windows/Automation/Peers/UIElementAutomationPeer.cs
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Original file line number Diff line number Diff line change
@@ -1,4 +1,4 @@
// Licensed to the .NET Foundation under one or more agreements.
// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.

using System.Windows.Input;
Expand Down Expand Up @@ -52,81 +52,51 @@ public static AutomationPeer FromElement(UIElement element)

return element.GetAutomationPeer();
}

///
override protected List<AutomationPeer> GetChildrenCore()

#nullable enable

/// <summary>
/// Retrieves the automation peers for the <see cref="UIElement"/> / <see cref="UIElement3D"/> children of this <see cref="_owner"/>.
/// </summary>
/// <returns>
/// Returns <see langword="null"/> if the <see cref="_owner"/> has no children of given type, otherwise a list of children.
/// </returns>
protected override List<AutomationPeer>? GetChildrenCore()
{
List<AutomationPeer> children = null;
List<AutomationPeer>? children = null;

iterate(_owner,
(IteratorCallback)delegate(AutomationPeer peer)
{
if (children == null)
children = new List<AutomationPeer>();
UIElementAutomationUtils.Iterate(_owner, ref children, static (ref List<AutomationPeer>? children, AutomationPeer peer) =>
{
children ??= new List<AutomationPeer>();
children.Add(peer);

children.Add(peer);
return (false);
});
return false;
});

return children;
}

///
internal static AutomationPeer GetRootAutomationPeer(Visual rootVisual, IntPtr hwnd)
internal static AutomationPeer? GetRootAutomationPeer(Visual rootVisual, IntPtr hwnd)
{
AutomationPeer root = null;
AutomationPeer? root = null;

iterate(rootVisual,
(IteratorCallback)delegate(AutomationPeer peer)
{
root = peer;
return (true);
});
UIElementAutomationUtils.Iterate(rootVisual, ref root, static (ref AutomationPeer? root, AutomationPeer peer) =>
{
root = peer;

return true;
});

if (root != null)
if (root is not null)
{
root.Hwnd = hwnd;
}

return root;
}

private delegate bool IteratorCallback(AutomationPeer peer);

//
private static bool iterate(DependencyObject parent, IteratorCallback callback)
{
bool done = false;

if(parent != null)
{
AutomationPeer peer = null;
int count = VisualTreeHelper.GetChildrenCount(parent);
for (int i = 0; i < count && !done; i++)
{
DependencyObject child = VisualTreeHelper.GetChild(parent, i);

if( child != null
&& child is UIElement
&& (peer = CreatePeerForElement((UIElement)child)) != null )
{
done = callback(peer);
}
else if ( child != null
&& child is UIElement3D
&& (peer = UIElement3DAutomationPeer.CreatePeerForElement(((UIElement3D)child))) != null )
{
done = callback(peer);
}
else
{
done = iterate(child, callback);
}
}
}

return done;
}
#nullable disable

///
override public object GetPattern(PatternInterface patternInterface)
Expand Down
51 changes: 51 additions & 0 deletions ...tNet.Wpf/src/PresentationCore/System/Windows/Automation/Peers/UIElementAutomationUtils.cs
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Original file line number Diff line number Diff line change
@@ -0,0 +1,51 @@
// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.

#nullable enable

using System.Windows.Media;

namespace System.Windows.Automation.Peers;

/// <summary>
/// Provides utility methods shared by <see cref="UIElementAutomationPeer"/> and <see cref="UIElement3DAutomationPeer"/>.
/// </summary>
internal static class UIElementAutomationUtils
{
/// <summary>
/// Generic callback for the <see cref="Iterate{T}"/> function.
/// </summary>
internal delegate bool UIElementIteratorCallback<T>(ref T? capture, AutomationPeer peer);

/// <summary>
/// Iterates through the children of the given <paramref name="parent"/> and either attempts to create
/// or retrieve the current <see cref="AutomationPeer"/> for the given <see cref="UIElement"/> / <see cref="UIElement3D"/>.
/// </summary>
internal static bool Iterate<T>(DependencyObject? parent, ref T? callbackParameter, UIElementIteratorCallback<T> callback)
{
bool done = false;

if (parent is not null)
{
int childrenCount = VisualTreeHelper.GetChildrenCount(parent);

for (int i = 0; i < childrenCount && !done; i++)
{
DependencyObject child = VisualTreeHelper.GetChild(parent, i);
AutomationPeer? peer;

if ((child is UIElement uiElement && (peer = uiElement.CreateAutomationPeer()) is not null) ||
(child is UIElement3D uiElement3D && (peer = uiElement3D.CreateAutomationPeer()) is not null))
{
done = callback(ref callbackParameter, peer);
}
else
{
done = Iterate(child, ref callbackParameter, callback);
}
}
}

return done;
}
}