// 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;
 
public partial class Control
{
    private readonly ref struct MultithreadSafeCallScope
    {
        // Use local stack variable rather than a refcount since we're
        // guaranteed that these 'scopes' are properly nested.
        private readonly bool _resultedInSet;
 
        private MultithreadSafeCallScope(bool resultedInSet)
            => _resultedInSet = resultedInSet;
 
        internal static MultithreadSafeCallScope Create()
        {
            // Only access the thread-local stuff if we're going to be
            // checking for illegal thread calling (no need to incur the
            // expense otherwise).
            if (CheckForIllegalCrossThreadCalls && !t_inCrossThreadSafeCall)
            {
                t_inCrossThreadSafeCall = true;
                return new MultithreadSafeCallScope(true);
            }
            else
            {
                return new MultithreadSafeCallScope(false);
            }
        }
 
        public void Dispose()
        {
            if (_resultedInSet)
            {
                t_inCrossThreadSafeCall = false;
            }
        }
    }
}