HighContrastHelper.cs source code in C# .NET

                        Code:
                         / 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / wpf / src / Framework / MS / Internal / Ink / HighContrastHelper.cs / 1305600 / HighContrastHelper.cs
                        
                        
                            //---------------------------------------------------------------------------- 
//
// File: HighContrastHelper.cs
//
// Description: 
//      A helper class for tracking the change of the system high contrast setting.
// 
// Features: 
//
// History: 
//  06/15/2005 waynezen:       Created
//
// Copyright (C) 2001 by Microsoft Corporation.  All rights reserved.
// 
//---------------------------------------------------------------------------
 
using System; 
using System.Collections.Generic;
using System.Diagnostics; 
using System.Security;
using System.Security.Permissions;
using System.Windows;
using System.Windows.Media; 
using System.Windows.Threading;
 
namespace MS.Internal.Ink 
{
    ///  
    /// HighContrastCallback Classs - An abstract helper class
    /// 
    internal abstract class HighContrastCallback
    { 
        /// 
        /// TurnHighContrastOn 
        ///  
        /// 
        internal abstract void TurnHighContrastOn(Color highContrastColor); 

        /// 
        /// TurnHighContrastOff
        ///  
        internal abstract void TurnHighContrastOff();
 
        ///  
        /// Returns the dispatcher if the object is associated to a UIContext.
        ///  
        internal abstract Dispatcher Dispatcher
        {
            get;
        } 
    }
 
    ///  
    /// StylusEditingBehavior - a base class for all stylus related editing behaviors
    ///  
    internal static class HighContrastHelper
    {
        //-------------------------------------------------------------------------------
        // 
        // Constructors
        // 
        //------------------------------------------------------------------------------- 

        #region Constructors 

        /// 
        /// Constructor
        ///  
        static HighContrastHelper()
        { 
            __highContrastCallbackList = new List(); 
            __increaseCount = 0;
        } 

        #endregion Constructors

 
        //--------------------------------------------------------------------------------
        // 
        // Internal Methods 
        //
        //------------------------------------------------------------------------------- 

        #region Internal Methods

        ///  
        /// Register the weak references for HighContrastCallback
        ///  
        ///  
        internal static void RegisterHighContrastCallback(HighContrastCallback highContrastCallback)
        { 
            lock ( __lock )
            {
                int count = __highContrastCallbackList.Count;
                int i = 0; 
                int j = 0;
 
                // Every 100 items, We go through the list to remove the references 
                // which have been collected by GC.
                if ( __increaseCount > CleanTolerance ) 
                {
                    while ( i < count )
                    {
                        WeakReference weakRef = __highContrastCallbackList[j]; 
                        if ( weakRef.IsAlive )
                        { 
                            j++; 
                        }
                        else 
                        {
                            // Remove the unavaliable reference from the list
                            __highContrastCallbackList.RemoveAt(j);
                        } 
                        i++;
                    } 
 
                    // Reset the count
                    __increaseCount = 0; 
                }

                __highContrastCallbackList.Add(new WeakReference(highContrastCallback));
                __increaseCount++; 
            }
        } 
 
        /// 
        /// The method is called from SystemResources.SystemThemeFilterMessage 
        /// 
        internal static void OnSettingChanged()
        {
            UpdateHighContrast(); 
        }
 
        #endregion Internal Methods 

        //-------------------------------------------------------------------------------- 
        //
        // Private Methods
        //
        //-------------------------------------------------------------------------------- 

        #region Private Methods 
 
        /// 
        /// UpdateHighContrast which calls out all the registered callbacks. 
        /// 
        private static void UpdateHighContrast()
        {
            lock ( __lock ) 
            {
                int count = __highContrastCallbackList.Count; 
                int i = 0; 
                int j = 0;
 
                // Now go through the list,
                // And we will notify the alive callbacks
                // or remove the references which have been collected by GC.
                while ( i < count ) 
                {
                    WeakReference weakRef = __highContrastCallbackList[j]; 
                    if ( weakRef.IsAlive ) 
                    {
                        HighContrastCallback highContrastCallback = weakRef.Target as HighContrastCallback; 

                        if ( highContrastCallback.Dispatcher != null )
                        {
                            highContrastCallback.Dispatcher.BeginInvoke(DispatcherPriority.Background, 
                                new UpdateHighContrastCallback(OnUpdateHighContrast),
                                highContrastCallback); 
                        } 
                        else
                        { 
                            OnUpdateHighContrast(highContrastCallback);
                        }

                        j++; 
                    }
                    else 
                    { 
                        // Remove the dead ones
                        __highContrastCallbackList.RemoveAt(j); 
                    }
                    i++;
                }
 
                // Reset the count
                __increaseCount = 0; 
 
            }
        } 

        private delegate void UpdateHighContrastCallback(HighContrastCallback highContrastCallback);

        ///  
        /// Invoke the callback
        ///  
        ///  
        private static void OnUpdateHighContrast(HighContrastCallback highContrastCallback)
        { 
            // Get the current setting.
            bool isHighContrast = SystemParameters.HighContrast;
            Color windowTextColor = SystemColors.WindowTextColor;
 
            if ( isHighContrast )
            { 
                highContrastCallback.TurnHighContrastOn(windowTextColor); 
            }
            else 
            {
                highContrastCallback.TurnHighContrastOff();
            }
        } 

        #endregion Private Methods 
 
        //-------------------------------------------------------------------------------
        // 
        // Private Fields
        //
        //--------------------------------------------------------------------------------
 
        #region Private Fields
 
        private static object                   __lock = new object(); 
        private static List      __highContrastCallbackList;
        private static int                      __increaseCount; 
        private const int                       CleanTolerance = 100;

        #endregion Private Fields
 

    } 
} 

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
// Copyright (c) Microsoft Corporation. All rights reserved.
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HighContrastHelper.cs source code in C# .NET

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