Code:
/ 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / wpf / src / Framework / System / Windows / Documents / WinEventHandler.cs / 1305600 / WinEventHandler.cs
//---------------------------------------------------------------------------- // //// Copyright (C) Microsoft Corporation. All rights reserved. // // // // Description: WinEventHandler implementation. // // History: // 02/04/2005 : yutakas - created. // //--------------------------------------------------------------------------- using System; using System.Collections; using System.Runtime.InteropServices; using System.ComponentModel; using System.Diagnostics; using System.Security; using System.Security.Permissions; using System.Windows.Threading; using MS.Win32; using MS.Internal; namespace System.Windows.Documents { internal class WinEventHandler : IDisposable { //----------------------------------------------------- // // Constructors // //----------------------------------------------------- #region Constructors // ctor that takes a range of events ////// Critical - as this calls the setter for _winEventProc.Value. /// Safe - as this doesn't allow an arbitrary value to be set. /// [SecurityCritical, SecurityTreatAsSafe] internal WinEventHandler(int eventMin, int eventMax) { _eventMin = eventMin; _eventMax = eventMax; _winEventProc.Value = new NativeMethods.WinEventProcDef(WinEventDefaultProc); // Keep the garbage collector from moving things around _gchThis = GCHandle.Alloc(_winEventProc.Value); // Workaround for bug 150666. Dispatcher dispatcher = Dispatcher.CurrentDispatcher; if (dispatcher != null) { dispatcher.ShutdownFinished += new EventHandler(OnDispatcherShutDown); } } ~WinEventHandler() { Clear(); } #endregion Constructors //------------------------------------------------------ // // Internal Methods // //----------------------------------------------------- #region Internal Methods public void Dispose() { // no need to call this finalizer. GC.SuppressFinalize(this); Clear(); } // callback for the class inherited from this. internal virtual void WinEventProc(int eventId, IntPtr hwnd) { } ////// Critical: This code frees the gchandle and is critical because it calls GCHandle /// TreatAsSafe: Ok to call free on a handle that we have allocated /// [SecurityCritical,SecurityTreatAsSafe] internal void Clear() { // Make sure that the hooks is uninitialzied. Stop(); // free GC handle. if (_gchThis.IsAllocated) { _gchThis.Free(); } } // install WinEvent hook and start getting the callback. ////// Critical - as this calls SetWinEventHook which has a SUC on it and also calls /// the setter for _hHook. /// Safe - as this does not allow an arbitrary method to be set up as a hook and /// also doesn't allow an aribtrary value to be set on _hHook.Value. /// [SecurityCritical, SecurityTreatAsSafe] internal void Start() { if (_gchThis.IsAllocated) { _hHook.Value = UnsafeNativeMethods.SetWinEventHook(_eventMin, _eventMax, IntPtr.Zero, _winEventProc.Value, 0, 0, NativeMethods.WINEVENT_OUTOFCONTEXT); if (_hHook.Value == IntPtr.Zero ) { Stop(); } } } // uninstall WinEvent hook. ////// Critical - as this calls UnhookWinEvent which has a SUC on it and also /// calls the setter for _hHook.Value. /// Safe - as this does not allow an arbitrary hook to be removed and sets /// _hHook.Value to IntPtr.Zero which is safe. /// [SecurityCritical, SecurityTreatAsSafe] internal void Stop() { if (_hHook.Value != IntPtr.Zero ) { UnsafeNativeMethods.UnhookWinEvent(_hHook.Value); _hHook.Value = IntPtr.Zero ; } } #endregion Internal Methods //------------------------------------------------------ // // Private Methods // //------------------------------------------------------ #region Private Methods private void WinEventDefaultProc(int winEventHook, int eventId, IntPtr hwnd, int idObject, int idChild, int eventThread, int eventTime) { WinEventProc(eventId , hwnd); } // Workaround for bug 150666. private void OnDispatcherShutDown(object sender, EventArgs args) { Stop(); } #endregion Private Methods //----------------------------------------------------- // // Private Fields // //------------------------------------------------------ #region Private Fields // min WinEvent. private int _eventMin; // max WinEvent. private int _eventMax; // hook handle private SecurityCriticalDataForSet_hHook; // the callback. private SecurityCriticalDataForSet _winEventProc; // GCHandle to keep the garbage collector from moving things around private GCHandle _gchThis; #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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