MediaContextNotificationWindow.cs source code in C# .NET

Source code for the .NET framework in C#

                        

Code:

/ DotNET / DotNET / 8.0 / untmp / WIN_WINDOWS / lh_tools_devdiv_wpf / Windows / wcp / Core / System / Windows / Media / MediaContextNotificationWindow.cs / 1 / MediaContextNotificationWindow.cs

                            //------------------------------------------------------------------------------ 
//
// 
//    Copyright (c) Microsoft Corporation.  All rights reserved.
//  
//
// Description: 
//      A wrapper for a top-level hidden window that is used to process 
//      messages broadcasted to top-level windows only (such as DWM's
//      WM_DWMCOMPOSITIONCHANGED). If the WPF application doesn't have 
//      a top-level window (as it is the case for XBAP applications),
//      such messages would have been ignored.
//
//----------------------------------------------------------------------------- 

using System; 
using System.Windows.Threading; 

using System.Collections; 
using System.Diagnostics;
using System.Windows.Media.Animation;
using System.Windows.Media.Composition;
using Microsoft.Win32; 
using Microsoft.Internal;
using MS.Internal; 
using MS.Win32; 
using System.Security;
using System.Security.Permissions; 

using SR=MS.Internal.PresentationCore.SR;
using SRID=MS.Internal.PresentationCore.SRID;
using UnsafeNativeMethods=MS.Win32.PresentationCore.UnsafeNativeMethods.MilCoreApi; 
using SafeNativeMethods=MS.Win32.PresentationCore.SafeNativeMethods;
 
namespace System.Windows.Media 
{
    ///  
    /// The MediaContextNotificationWindow structure provides its owner
    /// MediaContext with the ability to receive and forward window
    /// messages broadcasted to top-level windows.
    ///  
    internal struct MediaContextNotificationWindow
    { 
        //+--------------------------------------------------------------------- 
        //
        //  Internal Methods 
        //
        //---------------------------------------------------------------------

        #region Internal Methods 

        ///  
        /// Sets the owner MediaContext and creates the notification window. 
        /// 
        ///  
        ///     Critical - Creates an HwndWrapper and adds a hook.
        ///     TreatAsSafe: The _hwndNotification window is critical and this function is safe to call
        /// 
        [SecurityCritical, SecurityTreatAsSafe] 
        internal void CreateNotificationWindow(MediaContext ownerMediaContext)
        { 
            // Remember the pointer to the owner MediaContext that we'll forward the broadcasts to. 
            _ownerMediaContext = ownerMediaContext;
 
            // Create a top-level, invisible window so we can get the WM_DWMCOMPOSITIONCHANGED
            // and other DWM notifications that are broadcasted to top-level windows only.
            HwndWrapper hwndNotification;
            hwndNotification = new HwndWrapper(0, NativeMethods.WS_POPUP, 0, 0, 0, 0, 0, "MediaContextNotificationWindow", IntPtr.Zero, null); 

            _hwndNotificationHook = new HwndWrapperHook(MessageFilter); 
 
            _hwndNotification = new SecurityCriticalDataClass(hwndNotification);
            _hwndNotification.Value.AddHook(_hwndNotificationHook); 
        }

        ///
        ///     Critical - Calls dispose on the critical hwnd wrapper. 
        ///     TreatAsSafe: It is safe to dispose the wrapper
        /// 
        [SecurityCritical, SecurityTreatAsSafe] 
        internal void DisposeNotificationWindow()
        { 
            if (_hwndNotification != null)
                _hwndNotification.Value.Dispose();

            _hwndNotificationHook = null; 
            _hwndNotification = null;
 
            _ownerMediaContext = null; 
        }
 
        #endregion Internal Methods


        //+---------------------------------------------------------------------- 
        //
        //  Private Methods 
        // 
        //---------------------------------------------------------------------
 
        #region Private Methods

        /// 
        /// If any of the interesting broadcast messages is seen, forward them to the owner MediaContext. 
        /// 
        private IntPtr MessageFilter(IntPtr hwnd, int msg, IntPtr wParam, IntPtr lParam, ref bool handled) 
        { 
            Debug.Assert(_ownerMediaContext != null);
 
            if (msg == NativeMethods.WM_DWMCOMPOSITIONCHANGED)
            {
                _ownerMediaContext.OnDWMCompositionChanged();
            } 

            return IntPtr.Zero; 
        } 

        #endregion Private Methods 


        //+----------------------------------------------------------------------
        // 
        //  Private Fields
        // 
        //---------------------------------------------------------------------- 

        #region Private Fields 

        // The owner MediaContext
        private MediaContext _ownerMediaContext;
 
        // A top-level hidden window.
        private SecurityCriticalDataClass _hwndNotification; 
 
        // The message filter hook for the top-level hidden window.
        private HwndWrapperHook _hwndNotificationHook; 

        #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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