Fixing issue 3206: Label control accessibility reworking (#3208)

* Moving LabelAccessibleObject to a separate file. Adding unit tests.
* Ensuring Label supports UIA providers.

src/System.Windows.Forms/src/System/Windows/Forms/Label.LabelAccessibleObject.cs

@@ -0,0 +1,46 @@
+// 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 System.Runtime.InteropServices;
+using static Interop;
+
+namespace System.Windows.Forms
+{
+    public partial class Label
+    {
+        internal class LabelAccessibleObject : ControlAccessibleObject
+        {
+            private readonly Label _owningLabel;
+
+            public LabelAccessibleObject(Label owner) : base(owner)
+            {
+                _owningLabel = owner;
+            }
+
+            public override AccessibleRole Role
+            {
+                get
+                {
+                    AccessibleRole role = _owningLabel.AccessibleRole;
+
+                    if (role != AccessibleRole.Default)
+                    {
+                        return role;
+                    }
+
+                    return AccessibleRole.StaticText;
+                }
+            }
+
+            internal override object? GetPropertyValue(UiaCore.UIA propertyID)
+                => propertyID switch
+                {
+                    UiaCore.UIA.NamePropertyId => Name,
+                    UiaCore.UIA.AutomationIdPropertyId => _owningLabel.Name,
+                    UiaCore.UIA.ControlTypePropertyId => UiaCore.UIA.TextControlTypeId,
+                    _ => base.GetPropertyValue(propertyID)
+                };
+        }
+    }
+}

src/System.Windows.Forms/src/System/Windows/Forms/Label.cs

@@ -26,7 +26,7 @@ namespace System.Windows.Forms
     [ToolboxItem("System.Windows.Forms.Design.AutoSizeToolboxItem," + AssemblyRef.SystemDesign)]
     [SRDescription(nameof(SR.DescriptionLabel))]
     // If not for FormatControl, we could inherit from ButtonBase and get foreground images for free.
-    public class Label : Control, IAutomationLiveRegion
+    public partial class Label : Control, IAutomationLiveRegion
     {
         private static readonly object EVENT_TEXTALIGNCHANGED = new object();
 
@@ -1635,98 +1635,63 @@ namespace System.Windows.Forms
             }
         }
 
-        internal class LabelAccessibleObject : ControlAccessibleObject
+        /// <summary>
+        ///  Override ImageList.Indexer to support Label's ImageList semantics.
+        /// </summary>
+        internal class LabelImageIndexer : ImageList.Indexer
         {
-            public LabelAccessibleObject(Label owner) : base(owner)
+            private readonly Label owner;
+            private bool useIntegerIndex = true;
+
+            public LabelImageIndexer(Label owner)
             {
+                this.owner = owner;
             }
 
-            public override AccessibleRole Role
+            public override ImageList ImageList
+            {
+                get { return owner?.ImageList; }
+                set { Debug.Assert(false, "Setting the image list in this class is not supported"); }
+            }
+
+            public override string Key
+            {
+                get => base.Key;
+                set
+                {
+                    base.Key = value;
+                    useIntegerIndex = false;
+                }
+            }
+
+            public override int Index
+            {
+                get => base.Index;
+                set
+                {
+                    base.Index = value;
+                    useIntegerIndex = true;
+                }
+            }
+
+            public override int ActualIndex
             {
                 get
                 {
-                    AccessibleRole role = Owner.AccessibleRole;
-                    if (role != AccessibleRole.Default)
+                    if (useIntegerIndex)
                     {
-                        return role;
+                        // The behavior of label is to return the last item in the Images collection
+                        // if the index is currently set higher than the count.
+                        return (Index < ImageList.Images.Count) ? Index : ImageList.Images.Count - 1;
                     }
-                    return AccessibleRole.StaticText;
+                    else if (ImageList != null)
+                    {
+                        return ImageList.Images.IndexOfKey(Key);
+                    }
+
+                    return -1;
                 }
             }
-
-            internal override bool IsIAccessibleExSupported() => true;
-
-            internal override object GetPropertyValue(UiaCore.UIA propertyID)
-            {
-                switch (propertyID)
-                {
-                    case UiaCore.UIA.NamePropertyId:
-                        return Name;
-                    case UiaCore.UIA.ControlTypePropertyId:
-                        return UiaCore.UIA.TextControlTypeId;
-                }
-
-                return base.GetPropertyValue(propertyID);
-            }
-        }
-    }
-
-    /// <summary>
-    ///  Override ImageList.Indexer to support Label's ImageList semantics.
-    /// </summary>
-    internal class LabelImageIndexer : ImageList.Indexer
-    {
-        private readonly Label owner;
-        private bool useIntegerIndex = true;
-
-        public LabelImageIndexer(Label owner)
-        {
-            this.owner = owner;
-        }
-
-        public override ImageList ImageList
-        {
-            get { return owner?.ImageList; }
-            set { Debug.Assert(false, "Setting the image list in this class is not supported"); }
-        }
-
-        public override string Key
-        {
-            get => base.Key;
-            set
-            {
-                base.Key = value;
-                useIntegerIndex = false;
-            }
-        }
-
-        public override int Index
-        {
-            get => base.Index;
-            set
-            {
-                base.Index = value;
-                useIntegerIndex = true;
-            }
-        }
-
-        public override int ActualIndex
-        {
-            get
-            {
-                if (useIntegerIndex)
-                {
-                    // The behavior of label is to return the last item in the Images collection
-                    // if the index is currently set higher than the count.
-                    return (Index < ImageList.Images.Count) ? Index : ImageList.Images.Count - 1;
-                }
-                else if (ImageList != null)
-                {
-                    return ImageList.Images.IndexOfKey(Key);
-                }
-
-                return -1;
-            }
         }
     }
 }

src/System.Windows.Forms/tests/UnitTests/System/Windows/Forms/LabelTests.cs

@@ -216,6 +216,13 @@ namespace System.Windows.Forms.Tests
             Assert.Equal(-1, control.ImageIndex);
         }
 
+        [WinFormsFact]
+        public void Label_SupportsUiaProviders_returns_true()
+        {
+            using var label = new Label();
+            Assert.True(label.SupportsUiaProviders);
+        }
+
         public class SubLabel : Label
         {
             public new bool CanEnableIme => base.CanEnableIme;