More work on ComboBox OSX a11y.

Implement "Show Menu" and "Perform Press" actions.

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

@@ -222,11 +222,33 @@ public:
     return [self accessibilityTopLevelUIElement];
 }
 
-- (BOOL)accessibilityPerformPress
+- (BOOL)isAccessibilityExpanded
 {
-    if (!_peer->IsInvokeProvider())
+    if (!_peer->IsExpandCollapseProvider())
         return NO;
-    _peer->InvokeProvider_Invoke();
+    return _peer->ExpandCollapseProvider_IsExpanded();
+}
+
+- (void)setAccessibilityExpanded:(BOOL)accessibilityExpanded
+{
+    if (!_peer->IsExpandCollapseProvider())
+        return;
+    if (accessibilityExpanded)
+        _peer->ExpandCollapseProvider_Expand();
+    else
+        _peer->ExpandCollapseProvider_Collapse();
+}
+
+- (BOOL)accessibilityPerformPress
+{
+    if (_peer->IsInvokeProvider())
+    {
+        _peer->InvokeProvider_Invoke();
+    }
+    else if (_peer->IsExpandCollapseProvider())
+    {
+        _peer->ExpandCollapseProvider_Expand();
+    }
     return YES;
 }
 
@@ -250,11 +272,27 @@ public:
     return YES;
 }
 
+- (BOOL)accessibilityPerformShowMenu
+{
+    if (!_peer->IsExpandCollapseProvider())
+        return NO;
+    _peer->ExpandCollapseProvider_Expand();
+    return YES;
+}
+
 - (BOOL)isAccessibilitySelectorAllowed:(SEL)selector
 {
-    if (selector == @selector(accessibilityPerformPress))
+    if (selector == @selector(accessibilityPerformShowMenu))
+    {
+        return _peer->IsExpandCollapseProvider() && _peer->ExpandCollapseProvider_ShowsMenu();
+    }
+    else if (selector == @selector(isAccessibilityExpanded))
+    {
+        return _peer->IsExpandCollapseProvider();
+    }
+    else if (selector == @selector(accessibilityPerformPress))
     {
-        return _peer->IsInvokeProvider();
+        return _peer->IsInvokeProvider() || _peer->IsExpandCollapseProvider();
     }
     else if (selector == @selector(accessibilityPerformIncrement) ||
              selector == @selector(accessibilityPerformDecrement))

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

@@ -20,6 +20,7 @@ namespace Avalonia.Automation.Peers
         public new ComboBox Owner => (ComboBox)base.Owner;
 
         public ExpandCollapseState ExpandCollapseState => ToState(Owner.IsDropDownOpen);
+        public bool ShowsMenu => true;
         public void Collapse() => Owner.IsDropDownOpen = false;
         public void Expand() => Owner.IsDropDownOpen = true;
 

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

@@ -11,6 +11,15 @@
         /// </summary>
         ExpandCollapseState ExpandCollapseState { get; }
 
+        /// <summary>
+        /// Gets a value indicating whether expanding the element shows a menu of items to the user,
+        /// such as drop-down list.
+        /// </summary>
+        /// <remarks>
+        /// Used in OSX to enable the "Show Menu" action on the element.
+        /// </remarks>
+        bool ShowsMenu { get; }
+        
         /// <summary>
         /// Displays all child nodes, controls, or content of the control.
         /// </summary>

src/Avalonia.Native/AvnAutomationPeer.cs

@@ -1,5 +1,6 @@
 using System.Collections.Generic;
 using System.Linq;
+using Avalonia.Automation;
 using Avalonia.Automation.Peers;
 using Avalonia.Automation.Provider;
 using Avalonia.Native.Interop;
@@ -75,6 +76,19 @@ namespace Avalonia.Native
             return Wrap(result);
         }
 
+        public int IsExpandCollapseProvider() => (_inner is IExpandCollapseProvider).AsComBool();
+
+        public int ExpandCollapseProvider_IsExpanded() => ((IExpandCollapseProvider)_inner).ExpandCollapseState switch
+        {
+            ExpandCollapseState.Expanded => 1,
+            ExpandCollapseState.PartiallyExpanded => 1,
+            _ => 0,
+        };
+
+        public int ExpandCollapseProvider_ShowsMenu() => ((IExpandCollapseProvider)_inner).ShowsMenu.AsComBool();
+        public void ExpandCollapseProvider_Expand() => ((IExpandCollapseProvider)_inner).Expand();
+        public void ExpandCollapseProvider_Collapse() => ((IExpandCollapseProvider)_inner).Collapse();
+
         public int IsInvokeProvider() => (_inner is IInvokeProvider).AsComBool();
         public void InvokeProvider_Invoke() => ((IInvokeProvider)_inner).Invoke();
 

src/Avalonia.Native/avn.idl

@@ -816,6 +816,12 @@ interface IAvnAutomationPeer : IUnknown
      IAvnAutomationPeer* RootProvider_GetFocus();
      IAvnAutomationPeer* RootProvider_GetPeerFromPoint(AvnPoint point);
      
+     bool IsExpandCollapseProvider();
+     bool ExpandCollapseProvider_IsExpanded();
+     bool ExpandCollapseProvider_ShowsMenu();
+     void ExpandCollapseProvider_Expand();
+     void ExpandCollapseProvider_Collapse();
+     
      bool IsInvokeProvider();
      void InvokeProvider_Invoke();