// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
 
namespace System.Windows.Forms;
 
/// <summary>
///  We need a special way to defer to the ListView's image list for indexing purposes.
///  ListViewGroupImageIndexer is a class used to support <see cref="ListViewGroup.TitleImageIndex"/> and
///  <see cref="ListViewGroup.TitleImageKey"/>.
/// </summary>
internal class ListViewGroupImageIndexer : ImageList.Indexer
{
    private readonly ListViewGroup _owner;
 
    /// <summary>
    ///  Initializes a new instance of the <see cref="ListViewGroupImageIndexer"/> class.
    /// </summary>
    /// <param name="group">The <see cref="ListViewGroup"/> that this object belongs to.</param>
    public ListViewGroupImageIndexer(ListViewGroup group)
    {
        _owner = group;
    }
 
    /// <summary>
    ///  Gets the <see cref="ListView.GroupImageList"/> of the <see cref="ListView"/>
    ///  associated with the group.
    /// </summary>
    public override ImageList? ImageList
    {
        get => _owner.ListView?.GroupImageList;
        set => Debug.Fail("We should never set the image list");
    }
}