Allow embedded root automation peers.

native/Avalonia.Native/src/OSX/automation.mm

@@ -73,6 +73,13 @@ + (AvnAccessibilityElement *)acquire:(IAvnAutomationPeer *)peer
     if (peer->IsRootProvider())
     {
         auto window = peer->RootProvider_GetWindow();
+
+        if (window == nullptr)
+        {
+            NSLog(@"IRootProvider.PlatformImpl returned null or a non-WindowBaseImpl.");
+            return nil;
+        }
+
         auto holder = dynamic_cast<INSWindowHolder*>(window);
         auto view = holder->GetNSView();
         return [[AvnRootAccessibilityElement alloc] initWithPeer:peer owner:view];
@@ -284,8 +291,8 @@ - (id)accessibilityTopLevelUIElement
 
 - (id)accessibilityWindow
 {
-    id topLevel = [self accessibilityTopLevelUIElement];
-    return [topLevel isKindOfClass:[NSWindow class]] ? topLevel : nil;
+    auto rootPeer = _peer->GetVisualRoot();
+    return [AvnAccessibilityElement acquire:rootPeer];
 }
 
 - (BOOL)isAccessibilityExpanded

src/Avalonia.Controls/Automation/Peers/AutomationPeer.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using Avalonia.Automation.Provider;
 
 namespace Avalonia.Automation.Peers
 {
@@ -115,9 +116,14 @@ public abstract class AutomationPeer
         /// <summary>
         /// Gets the <see cref="AutomationPeer"/> that is the parent of this <see cref="AutomationPeer"/>.
         /// </summary>
-        /// <returns></returns>
         public AutomationPeer? GetParent() => GetParentCore();
 
+        /// <summary>
+        /// Gets the <see cref="AutomationPeer"/> that is the root of this <see cref="AutomationPeer"/>'s
+        /// visual tree.
+        /// </summary>
+        public AutomationPeer? GetVisualRoot() => GetVisualRootCore();
+
         /// <summary>
         /// Gets a value that indicates whether the element that is associated with this automation
         /// peer currently has keyboard focus.
@@ -247,6 +253,21 @@ protected virtual AutomationControlType GetControlTypeOverrideCore()
             return GetAutomationControlTypeCore();
         }
 
+        protected virtual AutomationPeer? GetVisualRootCore()
+        {
+            var peer = this;
+            var parent = peer.GetParent();
+
+            while (peer.GetProvider<IRootProvider>() is null && parent is not null)
+            {
+                peer = parent;
+                parent = peer.GetParent();
+            }
+
+            return peer;
+        }
+
+
         protected virtual bool IsContentElementOverrideCore()
         {
             return IsControlElement() && IsContentElementCore();

src/Avalonia.Controls/Automation/Peers/ControlAutomationPeer.cs

@@ -120,6 +120,13 @@ protected override IReadOnlyList<AutomationPeer> GetOrCreateChildrenCore()
             return _parent;
         }
 
+        protected override AutomationPeer? GetVisualRootCore()
+        {
+            if (Owner.GetVisualRoot() is Control c)
+                return CreatePeerForElement(c);
+            return null;
+        }
+
         /// <summary>
         /// Invalidates the peer's children and causes a re-read from <see cref="GetChildrenCore"/>.
         /// </summary>

src/Avalonia.Controls/Automation/Peers/ItemsControlAutomationPeer.cs

@@ -28,7 +28,7 @@ protected virtual IScrollProvider? Scroller
                 if (!_searchedForScrollable)
                 {
                     if (Owner.GetValue(ListBox.ScrollProperty) is Control scrollable)
-                        _scroller = GetOrCreate(scrollable) as IScrollProvider;
+                        _scroller = GetOrCreate(scrollable).GetProvider<IScrollProvider>();
                     _searchedForScrollable = true;
                 }
 

src/Avalonia.Controls/Automation/Peers/ListItemAutomationPeer.cs

@@ -22,7 +22,7 @@ public ISelectionProvider? SelectionContainer
                 if (Owner.Parent is Control parent)
                 {
                     var parentPeer = GetOrCreate(parent);
-                    return parentPeer as ISelectionProvider;
+                    return parentPeer.GetProvider<ISelectionProvider>();
                 }
 
                 return null;

src/Avalonia.Controls/Automation/Peers/WindowBaseAutomationPeer.cs

@@ -1,5 +1,6 @@
 using System;
 using System.ComponentModel;
+using System.Globalization;
 using Avalonia.Automation.Provider;
 using Avalonia.Controls;
 using Avalonia.Input;
@@ -32,7 +33,21 @@ protected override AutomationControlType GetAutomationControlTypeCore()
         public AutomationPeer? GetPeerFromPoint(Point p)
         {
             var hit = Owner.GetVisualAt(p)?.FindAncestorOfType<Control>(includeSelf: true);
-            return hit is object ? GetOrCreate(hit) : null;
+
+            if (hit is null)
+                return null;
+
+            var peer = GetOrCreate(hit);
+
+            while (peer != this && peer.GetProvider<IEmbeddedRootProvider>() is { } embedded)
+            {
+                var embeddedHit = embedded.GetPeerFromPoint(p);
+                if (embeddedHit is null)
+                    break;
+                peer = embeddedHit;
+            }
+
+            return peer;
         }
 
         protected void StartTrackingFocus()

src/Avalonia.Controls/Automation/Provider/IEmbeddedRootProvider.cs

@@ -0,0 +1,33 @@
+using System;
+using Avalonia.Automation.Peers;
+
+namespace Avalonia.Automation.Provider
+{
+    /// <summary>
+    /// Exposure methods and properties to support UI Automation client access to the root of an
+    /// automation tree hosted by another UI framework.
+    /// </summary>
+    /// <remarks>
+    /// This interface is implemented by the <see cref="AutomationPeer"/> class, and can be used
+    /// to embed an automation tree from a 3rd party UI framework that wishes to use Avalonia's
+    /// automation support.
+    /// </remarks>
+    public interface IEmbeddedRootProvider
+    {
+        /// <summary>
+        /// Gets the currently focused element.
+        /// </summary>
+        AutomationPeer? GetFocus();
+
+        /// <summary>
+        /// Gets the element at the specified point, expressed in top-level coordinates.
+        /// </summary>
+        /// <param name="p">The point.</param>
+        AutomationPeer? GetPeerFromPoint(Point p);
+
+        /// <summary>
+        /// Raised by the automation peer when the focus changes.
+        /// </summary>
+        event EventHandler? FocusChanged;
+    }
+}

src/Avalonia.Controls/Automation/Provider/IRootProvider.cs

@@ -4,11 +4,36 @@
 
 namespace Avalonia.Automation.Provider
 {
+    /// <summary>
+    /// Exposes methods and properties to support UI Automation client access to the root of an
+    /// automation tree.
+    /// </summary>
+    /// <remarks>
+    /// This interface is implemented by the <see cref="AutomationPeer"/> class, and should only
+    /// be implemented on true root elements, such as Windows. To embed an automation tree, use
+    /// <see cref="IEmbeddedRootProvider"/> instead.
+    /// </remarks>
     public interface IRootProvider
     {
+        /// <summary>
+        /// Gets the platform implementation of the TopLevel for the element.
+        /// </summary>
         ITopLevelImpl? PlatformImpl { get; }
+
+        /// <summary>
+        /// Gets the currently focused element.
+        /// </summary>
         AutomationPeer? GetFocus();
+
+        /// <summary>
+        /// Gets the element at the specified point, expressed in top-level coordinates.
+        /// </summary>
+        /// <param name="p">The point.</param>
         AutomationPeer? GetPeerFromPoint(Point p);
+
+        /// <summary>
+        /// Raised by the automation peer when the focus changes.
+        /// </summary>
         event EventHandler? FocusChanged;
     }
 }

src/Avalonia.Native/AvnAutomationPeer.cs

@@ -22,8 +22,8 @@ private AvnAutomationPeer(AutomationPeer inner)
         {
             _inner = inner;
             _inner.ChildrenChanged += (_, _) => Node?.ChildrenChanged();
-            if (inner is WindowBaseAutomationPeer window)
-                window.FocusChanged += (_, _) => Node?.FocusChanged(); 
+            if (inner is IRootProvider root)
+                root.FocusChanged += (_, _) => Node?.FocusChanged(); 
         }
 
         ~AvnAutomationPeer() => Node?.Dispose();
@@ -39,6 +39,7 @@ private AvnAutomationPeer(AutomationPeer inner)
         public IAvnAutomationPeer? LabeledBy => Wrap(_inner.GetLabeledBy());
         public IAvnString Name => _inner.GetName().ToAvnString();
         public IAvnAutomationPeer? Parent => Wrap(_inner.GetParent());
+        public IAvnAutomationPeer? VisualRoot => Wrap(_inner.GetVisualRoot());
 
         public int HasKeyboardFocus() => _inner.HasKeyboardFocus().AsComBool();
         public int IsContentElement() => _inner.IsContentElement().AsComBool();
@@ -48,14 +49,21 @@ private AvnAutomationPeer(AutomationPeer inner)
         public void SetFocus() => _inner.SetFocus();
         public int ShowContextMenu() => _inner.ShowContextMenu().AsComBool();
 
+        public void SetNode(IAvnAutomationNode node)
+        {
+            if (Node is not null)
+                throw new InvalidOperationException("The AvnAutomationPeer already has a node.");
+            Node = node;
+        }
+
         public IAvnAutomationPeer? RootPeer
         {
             get
             {
                 var peer = _inner;
                 var parent = peer.GetParent();
 
-                while (peer is not IRootProvider && parent is not null)
+                while (peer.GetProvider<IRootProvider>() is null && parent is not null)
                 {
                     peer = parent;
                     parent = peer.GetParent();
@@ -65,26 +73,23 @@ public IAvnAutomationPeer? RootPeer
             }
         }
 
-        public void SetNode(IAvnAutomationNode node)
-        {
-            if (Node is not null)
-                throw new InvalidOperationException("The AvnAutomationPeer already has a node.");
-            Node = node;
-        }
-
-        public int IsRootProvider() => (_inner is IRootProvider).AsComBool();
+        private IEmbeddedRootProvider EmbeddedRootProvider => GetProvider<IEmbeddedRootProvider>();
+        private IExpandCollapseProvider ExpandCollapseProvider => GetProvider<IExpandCollapseProvider>();
+        private IInvokeProvider InvokeProvider => GetProvider<IInvokeProvider>();
+        private IRangeValueProvider RangeValueProvider => GetProvider<IRangeValueProvider>();
+        private IRootProvider RootProvider => GetProvider<IRootProvider>();
+        private ISelectionItemProvider SelectionItemProvider => GetProvider<ISelectionItemProvider>();
+        private IToggleProvider ToggleProvider => GetProvider<IToggleProvider>();
+        private IValueProvider ValueProvider => GetProvider<IValueProvider>();
 
-        public IAvnWindowBase RootProvider_GetWindow()
-        {
-            var window = (WindowBase)((ControlAutomationPeer)_inner).Owner;
-            return ((WindowBaseImpl)window.PlatformImpl!).Native;
-        }
-
-        public IAvnAutomationPeer? RootProvider_GetFocus() => Wrap(((IRootProvider)_inner).GetFocus());
+        public int IsRootProvider() => IsProvider<IRootProvider>();
+
+        public IAvnWindowBase? RootProvider_GetWindow() => (RootProvider.PlatformImpl as WindowBaseImpl)?.Native;
+        public IAvnAutomationPeer? RootProvider_GetFocus() => Wrap(RootProvider.GetFocus());
 
         public IAvnAutomationPeer? RootProvider_GetPeerFromPoint(AvnPoint point)
         {
-            var result = ((IRootProvider)_inner).GetPeerFromPoint(point.ToAvaloniaPoint());
+            var result = RootProvider.GetPeerFromPoint(point.ToAvaloniaPoint());
 
             if (result is null)
                 return null;
@@ -103,46 +108,80 @@ public IAvnWindowBase RootProvider_GetWindow()
             return Wrap(result);
         }
 
-        public int IsExpandCollapseProvider() => (_inner is IExpandCollapseProvider).AsComBool();
 
-        public int ExpandCollapseProvider_GetIsExpanded() => ((IExpandCollapseProvider)_inner).ExpandCollapseState switch
+        public int IsEmbeddedRootProvider() => IsProvider<IEmbeddedRootProvider>();
+
+        public IAvnAutomationPeer? EmbeddedRootProvider_GetFocus() => Wrap(EmbeddedRootProvider.GetFocus());
+
+        public IAvnAutomationPeer? EmbeddedRootProvider_GetPeerFromPoint(AvnPoint point)
+        {
+            var result = EmbeddedRootProvider.GetPeerFromPoint(point.ToAvaloniaPoint());
+
+            if (result is null)
+                return null;
+
+            // The OSX accessibility APIs expect non-ignored elements when hit-testing.
+            while (!result.IsControlElement())
+            {
+                var parent = result.GetParent();
+
+                if (parent is not null)
+                    result = parent;
+                else
+                    break;
+            }
+
+            return Wrap(result);
+        }
+
+        public int IsExpandCollapseProvider() => IsProvider<IExpandCollapseProvider>();
+
+        public int ExpandCollapseProvider_GetIsExpanded() => ExpandCollapseProvider.ExpandCollapseState switch
         {
             ExpandCollapseState.Expanded => 1,
             ExpandCollapseState.PartiallyExpanded => 1,
             _ => 0,
         };
 
-        public int ExpandCollapseProvider_GetShowsMenu() => ((IExpandCollapseProvider)_inner).ShowsMenu.AsComBool();
-        public void ExpandCollapseProvider_Expand() => ((IExpandCollapseProvider)_inner).Expand();
-        public void ExpandCollapseProvider_Collapse() => ((IExpandCollapseProvider)_inner).Collapse();
+        public int ExpandCollapseProvider_GetShowsMenu() => ExpandCollapseProvider.ShowsMenu.AsComBool();
+        public void ExpandCollapseProvider_Expand() => ExpandCollapseProvider.Expand();
+        public void ExpandCollapseProvider_Collapse() => ExpandCollapseProvider.Collapse();
 
-        public int IsInvokeProvider() => (_inner is IInvokeProvider).AsComBool();
-        public void InvokeProvider_Invoke() => ((IInvokeProvider)_inner).Invoke();
+        public int IsInvokeProvider() => IsProvider<IInvokeProvider>();
+        public void InvokeProvider_Invoke() => InvokeProvider.Invoke();
 
-        public int IsRangeValueProvider() => (_inner is IRangeValueProvider).AsComBool();
-        public double RangeValueProvider_GetValue() => ((IRangeValueProvider)_inner).Value;
-        public double RangeValueProvider_GetMinimum() => ((IRangeValueProvider)_inner).Minimum;
-        public double RangeValueProvider_GetMaximum() => ((IRangeValueProvider)_inner).Maximum;
-        public double RangeValueProvider_GetSmallChange() => ((IRangeValueProvider)_inner).SmallChange;
-        public double RangeValueProvider_GetLargeChange() => ((IRangeValueProvider)_inner).LargeChange;
-        public void RangeValueProvider_SetValue(double value) => ((IRangeValueProvider)_inner).SetValue(value);
+        public int IsRangeValueProvider() => IsProvider<IRangeValueProvider>();
+        public double RangeValueProvider_GetValue() => RangeValueProvider.Value;
+        public double RangeValueProvider_GetMinimum() => RangeValueProvider.Minimum;
+        public double RangeValueProvider_GetMaximum() => RangeValueProvider.Maximum;
+        public double RangeValueProvider_GetSmallChange() => RangeValueProvider.SmallChange;
+        public double RangeValueProvider_GetLargeChange() => RangeValueProvider.LargeChange;
+        public void RangeValueProvider_SetValue(double value) => RangeValueProvider.SetValue(value);
 
-        public int IsSelectionItemProvider() => (_inner is ISelectionItemProvider).AsComBool();
-        public int SelectionItemProvider_IsSelected() => ((ISelectionItemProvider)_inner).IsSelected.AsComBool();
+        public int IsSelectionItemProvider() => IsProvider<ISelectionItemProvider>();
+        public int SelectionItemProvider_IsSelected() => SelectionItemProvider.IsSelected.AsComBool();
 
-        public int IsToggleProvider() => (_inner is IToggleProvider).AsComBool();
-        public int ToggleProvider_GetToggleState() => (int)((IToggleProvider)_inner).ToggleState;
-        public void ToggleProvider_Toggle() => ((IToggleProvider)_inner).Toggle();
+        public int IsToggleProvider() => IsProvider<IToggleProvider>();
+        public int ToggleProvider_GetToggleState() => (int)ToggleProvider.ToggleState;
+        public void ToggleProvider_Toggle() => ToggleProvider.Toggle();
 
-        public int IsValueProvider() => (_inner is IValueProvider).AsComBool();
-        public IAvnString ValueProvider_GetValue() => ((IValueProvider)_inner).Value.ToAvnString();
-        public void ValueProvider_SetValue(string value) => ((IValueProvider)_inner).SetValue(value);
+        public int IsValueProvider() => IsProvider<IValueProvider>();
+        public IAvnString ValueProvider_GetValue() => ValueProvider.Value.ToAvnString();
+        public void ValueProvider_SetValue(string value) => ValueProvider.SetValue(value);
 
         [return: NotNullIfNotNull("peer")]
         public static AvnAutomationPeer? Wrap(AutomationPeer? peer)
         {
             return peer is null ? null : s_wrappers.GetValue(peer, x => new(peer));
         }
+
+        private T GetProvider<T>()
+        {
+            return _inner.GetProvider<T>() ?? throw new InvalidOperationException(
+                $"The peer {_inner} does not implement {typeof(T)}.");
+        }
+
+        private int IsProvider<T>() => (_inner.GetProvider<T>() is not null).AsComBool();
     }
 
     internal class AvnAutomationPeerArray : NativeCallbackBase, IAvnAutomationPeerArray