Windows Automation tree breaking change

[Tobiidave]

Description

Dotnet 8 renders the controls in the Windows automation tree differently compared to earlier dotnet versions. Buttons in an itemscontrol can't be found anymore, breaking the existing automation.

Using the "Accessabilitiy Insights for Windows" shows a different graph compared to dotnet 6/7 (see below)

Reproduction Steps

WpfApp3.zip

Expected behavior

With <TargetFramework>net7.0-windows</TargetFramework> , the automation tree looks like pane "Desktop 1" window "MainWindow" title bar '' button "TopButton" button "ItemButton1"

Actual behavior

With <TargetFramework>net8.0-windows</TargetFramework>, the automation tree looks like

pane "Desktop 1" window "MainWindow" title bar '' button "TopButton" list view #note that here was the "ItemButton1" - now it is not present anymore!

Regression?

Yes

Known Workarounds

No response

Impact

The UI Tests for our applications breaks; need workarounds

Configuration

Microsoft.WindowsDesktop.App 8.0.1 Microsoft.NETCore.App 8.0.1 windows 10.19045.3803 x64

Vs2022

Other information

No response

[lindexi]

@Tobiidave Maybe this behavior be changed by https://github.com/dotnet/wpf/pull/6862

I'm not sure.

[Tobiidave]

I don't know how the 6862 affected this. But the problem exists in both 8.0.0 and 8.0.1

[psmulovics]

I do not think you can expect automation trees to stay intact between major version upgrades - I would consider it business-as-usual these getting broken on major upgrade.

[Tobiidave]

@psmulovics In this case the WPF controls change type and are not usable anymore, I edited and tried to emphasize this by a small comment. It is not only a tree re-ordering issue, but elements that were clickable can not be found anymore! Ofc, any suggested workarounds are welcome! We have paused dotnet8 migration due to this, the automation tech is central to our development.

[lindexi]

We have paused dotnet8 migration due to this

@Tobiidave Sorry hear that. I still haven't found the exact change code for this issues.

[jimm98y]

I've created a test app and I've tried to restore the original behavior simply by setting this in OnStartup:

System.AppContext.SetSwitch("Switch.System.Windows.Controls.ItemsControlDoesNotSupportAutomation", true);

Unfortunately, it looks like it's too late and the value is already set and cached. So I had to use reflection instead:

var accessibilitySwitches = Type.GetType("System.Windows.AccessibilitySwitches, WindowsBase, Version=8.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089");
var field = accessibilitySwitches.GetField("_ItemsControlDoesNotSupportAutomation", System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Static | BindingFlags.DeclaredOnly);
field.SetValue(null, 1);

This seems to fix the issue and restore the original pre-NET8 behavior. To test it, I used the following piece of code in the test app from this bug report:

public static void VerifyMainWindowAccessibility()
{
    AutomationElement mainWindow = AutomationElement.RootElement.FindFirst(TreeScope.Children, new PropertyCondition(AutomationElement.NameProperty, "MainWindow"));
    Debug.WriteLine(DumpUIATree(mainWindow));
}

private static string DumpUIATree(AutomationElement element)
{
    var s = element.Current.Name + " : " + element.Current.ControlType.ProgrammaticName;
    DumpChildrenRecursively(element, 1, ref s);
    return s;
}

private static List<AutomationElement> GetChildNodes(AutomationElement automationElement)
{
    var children = new List<AutomationElement>();
    TreeWalker walker = TreeWalker.ControlViewWalker;
    AutomationElement child = walker.GetFirstChild(automationElement);
    while (child != null)
    {
        children.Add(child);
        child = walker.GetNextSibling(child);
    }
    return children;
}

private static void DumpChildrenRecursively(AutomationElement node, int level, ref string s)
{
    var children = GetChildNodes(node);
    foreach (AutomationElement child in children)
    {
        if (child != null)
        {
            for (int i = 0; i < level; i++)
                s += "-";
            s += " " + child.Current.Name + " : " + child.Current.ControlType?.ProgrammaticName + "\r\n";
            DumpChildrenRecursively(child, level + 1, ref s);
        }
    }
}

NET8 before the fix:

- TopButton : ControlType.Button
-- TopButton : ControlType.Text
-  : ControlType.List
-- ItemButton1 : ControlType.DataItem
--- ItemButton1 : ControlType.Text

NET8 after the fix:

- TopButton : ControlType.Button
-- TopButton : ControlType.Text
- ItemButton1 : ControlType.Button
-- ItemButton1 : ControlType.Text

NET6 behavior:

- TopButton : ControlType.Button
-- TopButton : ControlType.Text
- ItemButton1 : ControlType.Button
-- ItemButton1 : ControlType.Text

[Kuldeep-MS]

I am investigating the issue from my end.

[Tobiidave]

Good work guys - but be sure to test this with the ms app "Accessibilities for Windows" to make sure it looks the same. It shows larger differences than what I see from your inspection using the TreeWalker-code above!

[walterlv]

I've tested this code below to set the AppContext switch and find it worked.

public class Program
{
    [STAThread]
    static void Main()
    {
        AppContext.SetSwitch("Switch.System.Windows.Controls.ItemsControlDoesNotSupportAutomation", true);

        var app = new App();
        app.InitializeComponent();
        app.Run();
    }
}

This means that if it is late on startup, it can be set before the WPF initialization which reflection is not needed. @jimm98y

[Tobiidave]

Hi. So now when .Net7 is out of support and this issue is blocking from moving to .Net8, what do think we should do with our app and +1000 customers?

[lindexi]

@Tobiidave Sorry, I do not think the PR can enter .NET 9

[Tobiidave]

So how would we handle these changes in the windows automation tree?

[Kuldeep-MS]

@Tobiidave - Could you please take a look at this comment, where the same scenario is explained in detail? Please let us know if it isn't working for you.

[Tobiidave]

Hi - I took the test project attached to this thread, added

    public App()
    {
        AppContext.SetSwitch("Switch.System.Windows.Controls.ItemsControlDoesNotSupportAutomation", true);

        // Create the startup window
        MainWindow mainWindow = new MainWindow();
        mainWindow.Show();
    }

But the automation tree did not change.