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// 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:
// 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.Runtime.InteropServices;
using System.Windows.Media.Animation;
using System.Windows.Media.Composition;
using Microsoft.Win32;
using MS.Internal;
using MS.Internal.PresentationCore;
using MS.Internal.Interop;
using MS.Win32;
using System.Security;
using SR=MS.Internal.PresentationCore.SR;
using DllImport=MS.Internal.PresentationCore.DllImport;
namespace System.Windows.Media
{
/// <summary>
/// The MediaContextNotificationWindow class provides its owner
/// MediaContext with the ability to receive and forward window
/// messages broadcasted to top-level windows.
/// </summary>
internal class MediaContextNotificationWindow : IDisposable
{
/// <summary>
/// Initializes static variables for this class.
/// </summary>
static MediaContextNotificationWindow()
{
s_channelNotifyMessage = UnsafeNativeMethods.RegisterWindowMessage("MilChannelNotify");
s_dwmRedirectionEnvironmentChanged = UnsafeNativeMethods.RegisterWindowMessage("DwmRedirectionEnvironmentChangedHint");
}
//+---------------------------------------------------------------------
//
// Internal Methods
//
//----------------------------------------------------------------------
#region Internal Methods
/// <summary>
/// Sets the owner MediaContext and creates the notification window.
/// </summary>
internal MediaContextNotificationWindow(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<HwndWrapper>(hwndNotification);
_hwndNotification.Value.AddHook(_hwndNotificationHook);
_isDisposed = false;
//
// On Vista, we need to know when the Magnifier goes on and off
// in order to switch to and from software rendering because the
// Vista Magnifier cannot magnify D3D content. To receive the
// window message informing us of this, we must tell the DWM
// we are MIL content.
//
// The Win7 Magnifier can magnify D3D content so it's not an
// issue there. In fact, Win7 doesn't even send the WM.
//
// If the DWM is not running, this call will result in NoOp.
//
ChangeWindowMessageFilter(s_dwmRedirectionEnvironmentChanged, 1 /* MSGFLT_ADD */);
MS.Internal.HRESULT.Check(MilContent_AttachToHwnd(_hwndNotification.Value.Handle));
}
public void Dispose()
{
if (!_isDisposed)
{
//
// If DWM is not running, this call will result in NoOp.
//
MS.Internal.HRESULT.Check(MilContent_DetachFromHwnd(_hwndNotification.Value.Handle));
_hwndNotification.Value.Dispose();
_hwndNotificationHook = null;
_hwndNotification = null;
_ownerMediaContext = null;
_isDisposed = true;
GC.SuppressFinalize(this);
}
}
#endregion Internal Methods
//+---------------------------------------------------------------------
//
// Private Methods
//
//----------------------------------------------------------------------
#region Private Methods
/// <summary>
/// Tells a channel to send notifications to a particular target's window.
/// </summary>
/// <param name="channel">
/// The channel from which we want notifications.
/// </param>
internal void SetAsChannelNotificationWindow()
{
ObjectDisposedException.ThrowIf(_isDisposed, typeof(MediaContextNotificationWindow));
_ownerMediaContext.Channel.SetNotificationWindow(_hwndNotification.Value.Handle, s_channelNotifyMessage);
}
/// <summary>
/// If any of the interesting broadcast messages is seen, forward them to the owner MediaContext.
/// </summary>
private IntPtr MessageFilter(IntPtr hwnd, int msg, IntPtr wParam, IntPtr lParam, ref bool handled)
{
ObjectDisposedException.ThrowIf(_isDisposed, typeof(MediaContextNotificationWindow));
WindowMessage message = (WindowMessage)msg;
Debug.Assert(_ownerMediaContext != null);
if (message == WindowMessage.WM_DWMCOMPOSITIONCHANGED)
{
//
// We need to register as MIL content to receive the Vista Magnifier messages
// (see comments in ctor).
//
// We're going to attempt to attach to DWM every time the desktop composition
// state changes to ensure that we properly handle DWM crashing/restarting/etc.
//
MS.Internal.HRESULT.Check(MilContent_AttachToHwnd(_hwndNotification.Value.Handle));
}
else if (message == s_channelNotifyMessage)
{
_ownerMediaContext.NotifyChannelMessage();
}
else if (message == s_dwmRedirectionEnvironmentChanged)
{
MediaSystem.NotifyRedirectionEnvironmentChanged();
}
return IntPtr.Zero;
}
[DllImport(DllImport.MilCore)]
private static extern int MilContent_AttachToHwnd(
IntPtr hwnd
);
[DllImport(DllImport.MilCore)]
private static extern int MilContent_DetachFromHwnd(
IntPtr hwnd
);
/// <summary>
/// Allow lower integrity applications to send specified window messages
/// in case we are elevated. Failure is non-fatal and on down-level
/// platforms this call will result in a no-op.
/// </summary>
private void ChangeWindowMessageFilter(WindowMessage message, uint flag)
{
// Find the address of ChangeWindowMessageFilter in user32.dll.
IntPtr user32Module = UnsafeNativeMethods.GetModuleHandle("user32.dll");
// Get the address of the function. If this fails it means the OS
// doesn't support this function, in which case we don't
// need to do anything further.
IntPtr functionAddress = UnsafeNativeMethods.GetProcAddressNoThrow(
new HandleRef(null, user32Module),
"ChangeWindowMessageFilter");
if (functionAddress != IntPtr.Zero)
{
// Convert the function pointer into a callable delegate and then call it
ChangeWindowMessageFilterNative function = Marshal.GetDelegateForFunctionPointer(
functionAddress,
typeof(ChangeWindowMessageFilterNative)) as ChangeWindowMessageFilterNative;
function(message, flag);
}
}
/// <summary>
/// Prototype for user32's ChangeWindowMessageFilter function, which we load dynamically on Vista+.
/// </summary>
[UnmanagedFunctionPointer(CallingConvention.Winapi)]
private delegate void ChangeWindowMessageFilterNative(WindowMessage message, uint flag);
#endregion Private Methods
//+---------------------------------------------------------------------
//
// Private Fields
//
//----------------------------------------------------------------------
#region Private Fields
private bool _isDisposed;
// The owner MediaContext
private MediaContext _ownerMediaContext;
// A top-level hidden window.
private SecurityCriticalDataClass<HwndWrapper> _hwndNotification;
// The message filter hook for the top-level hidden window.
private HwndWrapperHook _hwndNotificationHook;
// The window message used to announce a channel notification.
private static WindowMessage s_channelNotifyMessage;
// We receive this when the Vista Magnifier goes on/off
private static WindowMessage s_dwmRedirectionEnvironmentChanged;
#endregion Private Fields
}
}
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