Fix rectangle of the ListViewGroup (dotnet#4800)

Fixes dotnet#4778


## Proposed changes
- The issue with the incorrect rectangle is reproduced because the "FragmentRoot" property was not overridden. Added an override for the "FragmentRoot" property.
- Fixed issue with getting a rectangle for a ListViewGroup. Now, instead of the ListViewGroup index, we use the group ID. Fixed a issue with getting an incorrect ListViewGroup index.
- Added unit tests. Fixed typos in unit-tests naming


<!-- We are in TELL-MODE the following section must be completed -->

## Customer Impact
### Case 1
**Before fix:**
![Issue-4778-case1-before](https://user-images.githubusercontent.com/23376742/114997193-41c42500-9ea8-11eb-9d8d-dd2fed7be588.png)

**After fix:**
![Issue-4778-case1-after](https://user-images.githubusercontent.com/23376742/114997486-8e0f6500-9ea8-11eb-8e14-0aae753335ac.png)

### Case 2
**Before fix:**
![Issue-4778-case2-before](https://user-images.githubusercontent.com/23376742/114997915-0bd37080-9ea9-11eb-8203-d76619915de9.png)

**After fix:**
![Issue-4778-case2-after](https://user-images.githubusercontent.com/23376742/114997927-1130bb00-9ea9-11eb-80fe-bee59783f3cf.png)

## Regression? 

- Yes (from dotnet#3224)

## Risk

- Minimal

## Test methodology <!-- How did you ensure quality? -->
- CTI team
- unit tests

## Accessibility testing  <!-- Remove this section if PR does not change UI -->
- Inspector

## Test environment(s) <!-- Remove any that don't apply -->
- Microsoft Windows [Version 10.0.19041.388]
- .NET Core SDK: 6.0.100-preview.2.21155.3

src/System.Windows.Forms.Primitives/src/Interop/ComCtl32/Interop.LVGGR.cs

@@ -0,0 +1,17 @@
+// 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.
+
+internal static partial class Interop
+{
+    internal static partial class ComCtl32
+    {
+        public enum LVGGR
+        {
+            GROUP = 0,
+            HEADER = 1,
+            LABEL = 2,
+            SUBSETLINK = 3
+        }
+    }
+}

src/System.Windows.Forms/src/System/Windows/Forms/ListView.ListViewAccessibleObject.cs

@@ -26,11 +26,11 @@ internal override bool CanSelectMultiple
             internal override int ColumnCount
                 => _owningListView.Columns.Count;
 
-            private bool OwnerHasDefaultGroup
+            internal bool OwnerHasDefaultGroup
             {
                 get
                 {
-                    if (!_owningListView.IsHandleCreated || !_owningListView.ShowGroups || _owningListView.VirtualMode)
+                    if (!_owningListView.ShowGroups || _owningListView.VirtualMode)
                     {
                         return false;
                     }
@@ -77,7 +77,7 @@ internal override int[]? RuntimeId
             }
 
             // ListViewGroup are not displayed when the ListView is in "List" view
-            private bool ShowGroupAccessibleObject => _owningListView.View != View.List && _owningListView.GroupsEnabled;
+            internal bool ShowGroupAccessibleObject => _owningListView.View != View.List && _owningListView.GroupsEnabled;
 
             internal override UiaCore.IRawElementProviderFragment? ElementProviderFromPoint(double x, double y)
             {

src/System.Windows.Forms/src/System/Windows/Forms/ListView.cs

@@ -3501,22 +3501,6 @@ internal int GetColumnIndex(ColumnHeader ch)
             return -1;
         }
 
-        internal int GetGroupIndex(ListViewGroup owningGroup)
-        {
-            if (Groups.Count == 0)
-            {
-                return -1;
-            }
-
-            // Default group it's last group in accessibility and not specified in Groups collection, therefore default group index = Groups.Count
-            if (DefaultGroup == owningGroup)
-            {
-                return Groups.Count;
-            }
-
-            return Groups.IndexOf(owningGroup);
-        }
-
         /// <summary>
         ///  Returns the current ListViewItem corresponding to the specific
         ///  x,y co-ordinate.

src/System.Windows.Forms/src/System/Windows/Forms/ListViewGroup.ListViewGroupAccessibleObject.cs

@@ -4,6 +4,7 @@
 
 using System.Collections.Generic;
 using System.Drawing;
+using System.Runtime.InteropServices;
 using static System.Windows.Forms.ListView;
 using static Interop;
 using static Interop.ComCtl32;
@@ -42,28 +43,55 @@ public override Rectangle Bounds
             {
                 get
                 {
-                    if (!_owningListView.IsHandleCreated || _owningListView.VirtualMode)
+                    if (!_owningListView.IsHandleCreated || !_owningListViewAccessibilityObject.ShowGroupAccessibleObject)
                     {
                         return Rectangle.Empty;
                     }
 
-                    RECT groupRect = new RECT();
-                    User32.SendMessageW(_owningListView, (User32.WM)ComCtl32.LVM.GETGROUPRECT, (IntPtr)CurrentIndex, ref groupRect);
+                    if (GetVisibleItems().Count == 0)
+                    {
+                        return Rectangle.Empty;
+                    }
+
+                    int nativeGroupId = GetNativeGroupId();
+                    if (nativeGroupId == -1)
+                    {
+                        return Rectangle.Empty;
+                    }
 
-                    return new Rectangle(
-                        _owningListViewAccessibilityObject.Bounds.X + groupRect.left,
-                        _owningListViewAccessibilityObject.Bounds.Y + groupRect.top,
-                        groupRect.right - groupRect.left,
-                        groupRect.bottom - groupRect.top);
+                    LVGGR rectType = _owningGroup.CollapsedState == ListViewGroupCollapsedState.Collapsed
+                        ? LVGGR.HEADER
+                        : LVGGR.GROUP;
+
+                    // Get the native rectangle
+                    RECT groupRect = new();
+
+                    // Using the "top" property, we set which rectangle type of the group we want to get
+                    // This is described in more detail in https://docs.microsoft.com/windows/win32/controls/lvm-getgrouprect
+                    groupRect.top = (int)rectType;
+                    User32.SendMessageW(_owningListView, (User32.WM)LVM.GETGROUPRECT, (IntPtr)nativeGroupId, ref groupRect);
+
+                    // Using the following code, we limit the size of the ListViewGroup rectangle
+                    // so that it does not go beyond the rectangle of the ListView
+                    Rectangle listViewBounds = _owningListView.AccessibilityObject.Bounds;
+                    groupRect = _owningListView.RectangleToScreen(groupRect);
+                    groupRect.top = Math.Max(listViewBounds.Top, groupRect.top);
+                    groupRect.bottom = Math.Min(listViewBounds.Bottom, groupRect.bottom);
+                    groupRect.left = Math.Max(listViewBounds.Left, groupRect.left);
+                    groupRect.right = Math.Min(listViewBounds.Right, groupRect.right);
+
+                    return groupRect;
                 }
             }
 
-            private int CurrentIndex
+            internal int CurrentIndex
+                // The default group has 0 index, as it is always displayed first.
                 => _owningGroupIsDefault
-                    // Default group has the last index out of the Groups.Count
-                    // upper bound: so the DefaultGroup.Index == Groups.Count.
-                    ? _owningListView.Groups.Count
-                    : _owningListView.Groups.IndexOf(_owningGroup);
+                    ? 0
+                    // When calculating the index of other groups, we add a shift if the default group is displayed
+                    : _owningListViewAccessibilityObject.OwnerHasDefaultGroup
+                        ? _owningListView.Groups.IndexOf(_owningGroup) + 1
+                        : _owningListView.Groups.IndexOf(_owningGroup);
 
             public override string DefaultAction
                 => SR.AccessibleActionDoubleClick;
@@ -73,6 +101,8 @@ internal override UiaCore.ExpandCollapseState ExpandCollapseState
                     ? UiaCore.ExpandCollapseState.Collapsed
                     : UiaCore.ExpandCollapseState.Expanded;
 
+            internal override UiaCore.IRawElementProviderFragmentRoot FragmentRoot => _owningListView.AccessibilityObject;
+
             public override string Name
                 => _owningGroup.Header;
 
@@ -131,7 +161,26 @@ private bool GetNativeFocus()
                     return false;
                 }
 
-                return LVGS.FOCUSED == unchecked((LVGS)(long)User32.SendMessageW(_owningListView, (User32.WM)LVM.GETGROUPSTATE, (IntPtr)CurrentIndex, (IntPtr)LVGS.FOCUSED));
+                int nativeGroupId = GetNativeGroupId();
+                if (nativeGroupId == -1)
+                {
+                    return false;
+                }
+
+                return LVGS.FOCUSED == unchecked((LVGS)(long)User32.SendMessageW(_owningListView, (User32.WM)LVM.GETGROUPSTATE, (IntPtr)nativeGroupId, (IntPtr)LVGS.FOCUSED));
+            }
+
+            private unsafe int GetNativeGroupId()
+            {
+                LVGROUPW lvgroup = new LVGROUPW
+                {
+                    cbSize = (uint)sizeof(LVGROUPW),
+                    mask = LVGF.GROUPID,
+                };
+
+                return User32.SendMessageW(_owningListView, (User32.WM)LVM.GETGROUPINFOBYINDEX, (IntPtr)CurrentIndex, ref lvgroup) == IntPtr.Zero
+                    ? -1
+                    : lvgroup.iGroupId;
             }
 
             internal override object? GetPropertyValue(UiaCore.UIA propertyID)
@@ -157,6 +206,19 @@ private bool GetNativeFocus()
             internal IReadOnlyList<ListViewItem> GetVisibleItems()
             {
                 List<ListViewItem> visibleItems = new();
+                if (_owningGroupIsDefault)
+                {
+                    foreach (ListViewItem? listViewItem in _owningListView.Items)
+                    {
+                        if (listViewItem is not null && listViewItem.Group is null)
+                        {
+                            visibleItems.Add(listViewItem);
+                        }
+                    }
+
+                    return visibleItems;
+                }
+
                 foreach (ListViewItem listViewItem in _owningGroup.Items)
                 {
                     if (listViewItem.ListView is not null)
@@ -213,26 +275,13 @@ internal IReadOnlyList<ListViewItem> GetVisibleItems()
                     return null;
                 }
 
-                if (!_owningGroupIsDefault)
+                IReadOnlyList<ListViewItem> visibleItems = GetVisibleItems();
+                if (index < 0 || index >= visibleItems.Count)
                 {
-                    IReadOnlyList<ListViewItem> visibleItems = GetVisibleItems();
-                    if (index < 0 || index >= visibleItems.Count)
-                    {
-                        return null;
-                    }
-
-                    return visibleItems[index].AccessibilityObject;
-                }
-
-                foreach (ListViewItem? item in _owningListView.Items)
-                {
-                    if (item is not null && item.Group is null && index-- == 0)
-                    {
-                        return item.AccessibilityObject;
-                    }
+                    return null;
                 }
 
-                return null;
+                return visibleItems[index].AccessibilityObject;
             }
 
             private int GetChildIndex(AccessibleObject child)
@@ -300,23 +349,7 @@ public override int GetChildCount()
                     return -1;
                 }
 
-                if (_owningGroupIsDefault)
-                {
-                    int count = 0;
-                    foreach (ListViewItem? item in _owningListView.Items)
-                    {
-                        if (item is not null && item.Group is null)
-                        {
-                            count++;
-                        }
-                    }
-
-                    return count;
-                }
-                else
-                {
-                    return GetVisibleItems().Count;
-                }
+                return GetVisibleItems().Count;
             }
 
             internal override bool IsPatternSupported(UiaCore.UIA patternId)

src/System.Windows.Forms/src/System/Windows/Forms/ListViewItem.ListViewItemAccessibleObject.cs

@@ -179,7 +179,10 @@ internal override int[]? RuntimeId
                         runtimeId[0] = owningListViewRuntimeId[0];
                         runtimeId[1] = owningListViewRuntimeId[1];
                         runtimeId[2] = 4; // Win32-control specific RuntimeID constant, is used in similar Win32 controls and is used in WinForms controls for consistency.
-                        runtimeId[3] = _owningListView.GetGroupIndex(_owningGroup);
+                        runtimeId[3] = _owningGroup.AccessibilityObject is ListViewGroupAccessibleObject listViewGroupAccessibleObject
+                                        ? listViewGroupAccessibleObject.CurrentIndex
+                                        : -1;
+
                         runtimeId[4] = CurrentIndex;
 
                         return runtimeId;

src/System.Windows.Forms/tests/UnitTests/System/Windows/Forms/ListVIew.ListViewAccessibleObjectTests.cs

@@ -424,7 +424,7 @@ public static IEnumerable<object[]> ListViewAccessibleObject_OwnerHasDefaultGrou
                 {
                     foreach (bool createHandle in new[] { true, false })
                     {
-                        bool expected = showGroups && createHandle;
+                        bool expected = showGroups;
                         yield return new object[] { showGroups, createHandle, expected };
                     }
                 }