// 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.
 
//
//
// Description: Manager for the LostFocus event in the "weak event listener"
//              pattern.  See WeakEventTable.cs for an overview.
//
 
using System;
using System.Windows;       // WeakEventManager
using MS.Internal;          // Helper
 
namespace System.Windows
{
    /// <summary>
    /// Manager for the DependencyObject.LostFocus event.
    /// </summary>
    public class LostFocusEventManager : WeakEventManager
    {
        #region Constructors
 
        //
        //  Constructors
        //
 
        private LostFocusEventManager()
        {
        }
 
        #endregion Constructors
 
        #region Public Methods
 
        //
        //  Public Methods
        //
 
        /// <summary>
        /// Add a listener to the given source's event.
        /// </summary>
        public static void AddListener(DependencyObject source, IWeakEventListener listener)
        {
            ArgumentNullException.ThrowIfNull(source);
            ArgumentNullException.ThrowIfNull(listener);
 
            CurrentManager.ProtectedAddListener(source, listener);
        }
 
        /// <summary>
        /// Remove a listener to the given source's event.
        /// </summary>
        public static void RemoveListener(DependencyObject source, IWeakEventListener listener)
        {
            ArgumentNullException.ThrowIfNull(source);
            ArgumentNullException.ThrowIfNull(listener);
 
            CurrentManager.ProtectedRemoveListener(source, listener);
        }
 
        /// <summary>
        /// Add a handler for the given source's event.
        /// </summary>
        public static void AddHandler(DependencyObject source, EventHandler<RoutedEventArgs> handler)
        {
            ArgumentNullException.ThrowIfNull(handler);
 
            CurrentManager.ProtectedAddHandler(source, handler);
        }
 
        /// <summary>
        /// Remove a handler for the given source's event.
        /// </summary>
        public static void RemoveHandler(DependencyObject source, EventHandler<RoutedEventArgs> handler)
        {
            ArgumentNullException.ThrowIfNull(handler);
 
            CurrentManager.ProtectedRemoveHandler(source, handler);
        }
 
        #endregion Public Methods
 
        #region Protected Methods
 
        //
        //  Protected Methods
        //
 
        /// <summary>
        /// Return a new list to hold listeners to the event.
        /// </summary>
        protected override ListenerList NewListenerList()
        {
            return new ListenerList<RoutedEventArgs>();
        }
 
        /// <summary>
        /// Listen to the given source for the event.
        /// </summary>
        protected override void StartListening(object source)
        {
            DependencyObject typedSource = (DependencyObject)source;
            FrameworkElement fe;
            FrameworkContentElement fce;
            Helper.DowncastToFEorFCE(typedSource, out fe, out fce, true);
 
            if (fe != null)
                fe.LostFocus += new RoutedEventHandler(OnLostFocus);
            else if (fce != null)
                fce.LostFocus += new RoutedEventHandler(OnLostFocus);
        }
 
        /// <summary>
        /// Stop listening to the given source for the event.
        /// </summary>
        protected override void StopListening(object source)
        {
            DependencyObject typedSource = (DependencyObject)source;
            FrameworkElement fe;
            FrameworkContentElement fce;
            Helper.DowncastToFEorFCE(typedSource, out fe, out fce, true);
 
            if (fe != null)
                fe.LostFocus -= new RoutedEventHandler(OnLostFocus);
            else if (fce != null)
                fce.LostFocus -= new RoutedEventHandler(OnLostFocus);
        }
 
        #endregion Protected Methods
 
        #region Private Properties
 
        //
        //  Private Properties
        //
 
        // get the event manager for the current thread
        private static LostFocusEventManager CurrentManager
        {
            get
            {
                Type managerType = typeof(LostFocusEventManager);
                LostFocusEventManager manager = (LostFocusEventManager)GetCurrentManager(managerType);
 
                // at first use, create and register a new manager
                if (manager == null)
                {
                    manager = new LostFocusEventManager();
                    SetCurrentManager(managerType, manager);
                }
 
                return manager;
            }
        }
 
        #endregion Private Properties
 
        #region Private Methods
 
        //
        //  Private Methods
        //
 
        // event handler for LostFocus event
        private void OnLostFocus(object sender, RoutedEventArgs args)
        {
            DeliverEvent(sender, args);
        }
 
        #endregion Private Methods
    }
}