Adding Splitter UIA accessibility (#3246)

src/System.Windows.Forms/src/PublicAPI.Unshipped.txt

@@ -1,6 +1,7 @@
+~override System.Windows.Forms.Splitter.CreateAccessibilityInstance() -> System.Windows.Forms.AccessibleObject
 System.Windows.Forms.ListViewGroup.TitleImageIndex.get -> int
 System.Windows.Forms.ListViewGroup.TitleImageIndex.set -> void
 System.Windows.Forms.ListViewGroup.TitleImageKey.get -> string!
 System.Windows.Forms.ListViewGroup.TitleImageKey.set -> void
 ~System.Windows.Forms.ListView.GroupImageList.get -> System.Windows.Forms.ImageList
-~System.Windows.Forms.ListView.GroupImageList.set -> void
+~System.Windows.Forms.ListView.GroupImageList.set -> void

src/System.Windows.Forms/src/System/Windows/Forms/Splitter.SplitterAccessibleObject.cs

@@ -0,0 +1,34 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using static Interop;
+
+namespace System.Windows.Forms
+{
+    public partial class Splitter
+    {
+        internal class SplitterAccessibleObject : ControlAccessibleObject
+        {
+            internal SplitterAccessibleObject(Splitter owner) : base(owner)
+            {
+            }
+
+            internal override object? GetPropertyValue(UiaCore.UIA propertyID)
+                => propertyID switch
+                {
+                    UiaCore.UIA.NamePropertyId
+                        => Name,
+                    UiaCore.UIA.AutomationIdPropertyId
+                        => Owner.Name,
+                    UiaCore.UIA.ControlTypePropertyId
+                        => UiaCore.UIA.PaneControlTypeId,
+                    UiaCore.UIA.IsKeyboardFocusablePropertyId
+                        // This is necessary for compatibility with MSAA proxy:
+                        // IsKeyboardFocusable = true regardless the control is enabled/disabled.
+                        => true,
+                    _ => base.GetPropertyValue(propertyID)
+                };
+        }
+    }
+}

src/System.Windows.Forms/src/System/Windows/Forms/Splitter.cs

@@ -22,7 +22,7 @@ namespace System.Windows.Forms
     [DefaultProperty(nameof(Dock))]
     [SRDescription(nameof(SR.DescriptionSplitter))]
     [Designer("System.Windows.Forms.Design.SplitterDesigner, " + AssemblyRef.SystemDesign)]
-    public class Splitter : Control
+    public partial class Splitter : Control
     {
         private const int DRAW_START = 1;
         private const int DRAW_MOVE = 2;
@@ -207,6 +207,9 @@ namespace System.Windows.Forms
             }
         }
 
+        protected override AccessibleObject CreateAccessibilityInstance()
+            => new SplitterAccessibleObject(this);
+
         /// <summary>
         ///  Returns the parameters needed to create the handle.  Inheriting classes
         ///  can override this to provide extra functionality.  They should not,
@@ -428,6 +431,8 @@ namespace System.Windows.Forms
             }
         }
 
+        internal override bool SupportsUiaProviders => true;
+
         [Browsable(false)]
         [EditorBrowsable(EditorBrowsableState.Never)]
         new public bool TabStop

src/System.Windows.Forms/tests/UnitTests/AccessibleObjects/Splitter.SplitterAccessibleObjectTests.cs

@@ -0,0 +1,127 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Xunit;
+using static Interop.UiaCore;
+
+namespace System.Windows.Forms.Tests
+{
+    public class Splitter_SplitterAccessibleObjectTests
+    {
+        [WinFormsFact]
+        public void SplitterAccessibleObject_Ctor_NullControl_ThrowsArgumentNullException()
+        {
+            Assert.Throws<ArgumentNullException>("ownerControl", () => new Splitter.SplitterAccessibleObject(null));
+        }
+
+        [WinFormsFact]
+        public void SplitterAccessibleObject_Ctor_Default()
+        {
+            using var splitter = new Splitter();
+            Assert.False(splitter.IsHandleCreated);
+            var splitterAccessibleObject = new Splitter.SplitterAccessibleObject(splitter);
+
+            Assert.NotNull(splitterAccessibleObject.Owner);
+            // TODO: ControlAccessibleObject shouldn't force handle creation, tracked in https://github.com/dotnet/winforms/issues/3062
+            Assert.True(splitter.IsHandleCreated);
+        }
+
+        [WinFormsFact]
+        public void SplitterAccessibleObject_Descrpition_ReturnsExpected()
+        {
+            using var splitter = new Splitter
+            {
+                AccessibleDescription = "TestDescription"
+            };
+
+            Assert.False(splitter.IsHandleCreated);
+            var splitterAccessibleObject = new Splitter.SplitterAccessibleObject(splitter);
+
+            Assert.Equal("TestDescription", splitterAccessibleObject.Description);
+            // TODO: ControlAccessibleObject shouldn't force handle creation, tracked in https://github.com/dotnet/winforms/issues/3062
+            Assert.True(splitter.IsHandleCreated);
+        }
+
+        [WinFormsFact]
+        public void SplitterAccessibleObject_Name_ReturnsExpected()
+        {
+            using var splitter = new Splitter
+            {
+                AccessibleName = "TestName"
+            };
+
+            Assert.False(splitter.IsHandleCreated);
+            var splitterAccessibleObject = new Splitter.SplitterAccessibleObject(splitter);
+
+            Assert.Equal("TestName", splitterAccessibleObject.Name);
+            // TODO: ControlAccessibleObject shouldn't force handle creation, tracked in https://github.com/dotnet/winforms/issues/3062
+            Assert.True(splitter.IsHandleCreated);
+        }
+
+        [WinFormsFact]
+        public void SplitterAccessibleObject_CustomRole_ReturnsExpected()
+        {
+            using var splitter = new Splitter
+            {
+                AccessibleRole = AccessibleRole.PushButton
+            };
+
+            Assert.False(splitter.IsHandleCreated);
+            var splitterAccessibleObject = new Splitter.SplitterAccessibleObject(splitter);
+
+            Assert.Equal(AccessibleRole.PushButton, splitterAccessibleObject.Role);
+            // TODO: ControlAccessibleObject shouldn't force handle creation, tracked in https://github.com/dotnet/winforms/issues/3062
+            Assert.True(splitter.IsHandleCreated);
+        }
+
+        [WinFormsFact]
+        public void SplitterAccessibleObject_DefaultRole_ReturnsExpected()
+        {
+            using var splitter = new Splitter();
+            Assert.False(splitter.IsHandleCreated);
+            var splitterAccessibleObject = new Splitter.SplitterAccessibleObject(splitter);
+
+            Assert.Equal(AccessibleRole.Client, splitterAccessibleObject.Role);
+            // TODO: ControlAccessibleObject shouldn't force handle creation, tracked in https://github.com/dotnet/winforms/issues/3062
+            Assert.True(splitter.IsHandleCreated);
+        }
+
+        [WinFormsTheory]
+        [InlineData((int)UIA.NamePropertyId, "TestName")]
+        [InlineData((int)UIA.ControlTypePropertyId, UIA.PaneControlTypeId)]
+        [InlineData((int)UIA.IsKeyboardFocusablePropertyId, true)]
+        [InlineData((int)UIA.AutomationIdPropertyId, "Splitter1")]
+        public void SplitterAccessibleObject_GetPropertyValue_Invoke_ReturnsExpected(int propertyID, object expected)
+        {
+            using var splitter = new Splitter
+            {
+                Name = "Splitter1",
+                AccessibleName = "TestName"
+            };
+
+            Assert.False(splitter.IsHandleCreated);
+            var splitterAccessibleObject = new Splitter.SplitterAccessibleObject(splitter);
+            object value = splitterAccessibleObject.GetPropertyValue((UIA)propertyID);
+
+            Assert.Equal(expected, value);
+            // TODO: ControlAccessibleObject shouldn't force handle creation, tracked in https://github.com/dotnet/winforms/issues/3062
+            Assert.True(splitter.IsHandleCreated);
+        }
+
+        [WinFormsFact]
+        public void SplitterAccessibleObject_IsPatternSupported_Invoke_ReturnsTrue_ForLegacyIAccessiblePattern()
+        {
+            using var splitter = new Splitter
+            {
+                Name = "Splitter1"
+            };
+            Assert.False(splitter.IsHandleCreated);
+            var splitterAccessibleObject = new Splitter.SplitterAccessibleObject(splitter);
+
+            Assert.True(splitterAccessibleObject.IsPatternSupported(UIA.LegacyIAccessiblePatternId));
+            // TODO: ControlAccessibleObject shouldn't force handle creation, tracked in https://github.com/dotnet/winforms/issues/3062
+            Assert.True(splitter.IsHandleCreated);
+        }
+    }
+}