From e08c7f8149e45abac786637e44523e4a25fb139b Mon Sep 17 00:00:00 2001
From: Jumar Macato <16554748+jmacato@users.noreply.github.com>
Date: Wed, 17 Jun 2026 03:47:25 +0800
Subject: [PATCH] Expose tree item selection to macOS accessibility (#21598)

TreeViewItemAutomationPeer implements ISelectionItemProvider, and AvnAccessibilityElement maps setAccessibilitySelected to it, so AX clients can select a TreeViewItem.
---
 native/Avalonia.Native/src/OSX/automation.mm  | 10 ++++
 .../Peers/TreeViewItemAutomationPeer.cs       | 49 ++++++++++++++++++-
 src/Avalonia.Native/AvnAutomationPeer.cs      |  1 +
 src/Avalonia.Native/avn.idl                   |  1 +
 4 files changed, 59 insertions(+), 2 deletions(-)

diff --git a/native/Avalonia.Native/src/OSX/automation.mm b/native/Avalonia.Native/src/OSX/automation.mm
index 7897a76973..f355634de4 100644
--- a/native/Avalonia.Native/src/OSX/automation.mm
+++ b/native/Avalonia.Native/src/OSX/automation.mm
@@ -474,6 +474,12 @@
     return NO;
 }
 
+- (void)setAccessibilitySelected:(BOOL)accessibilitySelected
+{
+    if (accessibilitySelected && _peer->IsSelectionItemProvider())
+        _peer->SelectionItemProvider_Select();
+}
+
 - (BOOL)isAccessibilitySelectorAllowed:(SEL)selector
 {
     if (selector == @selector(setAccessibilityValue:))
@@ -492,6 +498,10 @@
     {
         return _peer->IsInvokeProvider() || _peer->IsExpandCollapseProvider() || _peer->IsToggleProvider();
     }
+    else if (selector == @selector(setAccessibilitySelected:))
+    {
+        return _peer->IsSelectionItemProvider();
+    }
     else if (selector == @selector(accessibilityPerformIncrement) ||
              selector == @selector(accessibilityPerformDecrement) ||
              selector == @selector(accessibilityMinValue) ||
diff --git a/src/Avalonia.Controls/Automation/Peers/TreeViewItemAutomationPeer.cs b/src/Avalonia.Controls/Automation/Peers/TreeViewItemAutomationPeer.cs
index 9629a75267..74bbf53ef9 100644
--- a/src/Avalonia.Controls/Automation/Peers/TreeViewItemAutomationPeer.cs
+++ b/src/Avalonia.Controls/Automation/Peers/TreeViewItemAutomationPeer.cs
@@ -1,14 +1,59 @@
+using Avalonia.Automation.Provider;
 using Avalonia.Controls;
 
 namespace Avalonia.Automation.Peers;
 
-public class TreeViewItemAutomationPeer : ItemsControlAutomationPeer
+public class TreeViewItemAutomationPeer : ItemsControlAutomationPeer,
+    ISelectionItemProvider
 {
     public TreeViewItemAutomationPeer(TreeViewItem owner)
         : base(owner)
     {
     }
-   
+
+    public bool IsSelected => Owner.GetValue(TreeViewItem.IsSelectedProperty);
+
+    public ISelectionProvider? SelectionContainer
+    {
+        get
+        {
+            if (Owner is TreeViewItem { TreeViewOwner: { } treeView })
+            {
+                var parentPeer = GetOrCreate(treeView);
+                return parentPeer.GetProvider<ISelectionProvider>();
+            }
+
+            return null;
+        }
+    }
+
+    public void Select()
+    {
+        EnsureEnabled();
+
+        if (Owner is TreeViewItem item)
+        {
+            item.TreeViewOwner?.SelectedItems.Clear();
+            item.IsSelected = true;
+        }
+    }
+
+    void ISelectionItemProvider.AddToSelection()
+    {
+        EnsureEnabled();
+
+        if (Owner is TreeViewItem item)
+            item.IsSelected = true;
+    }
+
+    void ISelectionItemProvider.RemoveFromSelection()
+    {
+        EnsureEnabled();
+
+        if (Owner is TreeViewItem item)
+            item.IsSelected = false;
+    }
+
     protected override AutomationControlType GetAutomationControlTypeCore()
     {
         return AutomationControlType.TreeItem;
diff --git a/src/Avalonia.Native/AvnAutomationPeer.cs b/src/Avalonia.Native/AvnAutomationPeer.cs
index 4a679e3ed7..b448d5cb1a 100644
--- a/src/Avalonia.Native/AvnAutomationPeer.cs
+++ b/src/Avalonia.Native/AvnAutomationPeer.cs
@@ -187,6 +187,7 @@ namespace Avalonia.Native
 
         public int IsSelectionItemProvider() => IsProvider<ISelectionItemProvider>();
         public int SelectionItemProvider_IsSelected() => SelectionItemProvider.IsSelected.AsComBool();
+        public void SelectionItemProvider_Select() => SelectionItemProvider.Select();
 
         public IAvnAutomationPeer? ScrollProvider_GetHorizontalScrollBar()
             => _inner is ScrollViewerAutomationPeer scrollViewer ? Wrap(scrollViewer.GetHorizontalScrollBarPeer()) : null;
diff --git a/src/Avalonia.Native/avn.idl b/src/Avalonia.Native/avn.idl
index a1b57f7d14..5b1b97fa37 100644
--- a/src/Avalonia.Native/avn.idl
+++ b/src/Avalonia.Native/avn.idl
@@ -1318,6 +1318,7 @@ interface IAvnAutomationPeer : IUnknown
      
      bool IsSelectionItemProvider();
      bool SelectionItemProvider_IsSelected();
+     void SelectionItemProvider_Select();
 
      IAvnAutomationPeer* ScrollProvider_GetHorizontalScrollBar();
      IAvnAutomationPeer* ScrollProvider_GetVerticalScrollBar();