ManagedWndProcTracker.cs source code in C# .NET

                        Code:
                         / DotNET / DotNET / 8.0 / untmp / WIN_WINDOWS / lh_tools_devdiv_wpf / Windows / wcp / Shared / MS / Win32 / ManagedWndProcTracker.cs / 1 / ManagedWndProcTracker.cs
                        
                        
                            //#define LOGGING 

using System;
using System.Collections;
using System.Threading; 

using System.Runtime.InteropServices; 
using MS.Internal; 
using System.Security;
using System.Security.Permissions; 

// The SecurityHelper class differs between assemblies and could not actually be
//  shared, so it is duplicated across namespaces to prevent name collision.
#if WINDOWS_BASE 
    using MS.Internal.WindowsBase;
#elif PRESENTATION_CORE 
    using MS.Internal.PresentationCore; 
#elif PRESENTATIONFRAMEWORK
    using MS.Internal.PresentationFramework; 
#elif DRT
    using MS.Internal.Drt;
#else
#error Attempt to use a class (duplicated across multiple namespaces) from an unknown assembly. 
#endif
 
namespace MS.Win32 
{
    internal static class ManagedWndProcTracker 
    {
        /// 
        ///     Critical: This code calls into Link demanded methods to attach handlers
        ///     TreatAsSafe: This code does not take any parameter or return state. 
        ///     It simply attaches private call back.
        ///  
        [SecurityCritical,SecurityTreatAsSafe] 
        static ManagedWndProcTracker()
        { 
            // Listen for ProcessExit so we can detach ourselves when the CLR shuts down
            // and avoid unmanaged code from calling back in to managed code during shutdown.
            AppDomain.CurrentDomain.ProcessExit += new EventHandler(OnAppDomainProcessExit);
            AppDomain.CurrentDomain.DomainUnload += new EventHandler(OnAppDomainProcessExit); 
        }
 
        ///  
        ///     Critical: Uses critical member _hwndList
        ///  
        [SecurityCritical]
        internal static void TrackHwndSubclass(HwndSubclass subclass, IntPtr hwnd)
        {
            lock (_hwndList) 
            {
                // We use HwndSubclass as the key and the hwnd ptr as the value. 
                // This supports the case where two (or more) HwndSubclasses 
                // get attached to the same Hwnd.  At AppDomain shutdown, we may
                // end up sending the Detach message to the Hwnd more than once, 
                // but that won't cause any harm.
                _hwndList[subclass] = hwnd;
            }
 
#if LOGGING
            LogStartHWND(hwnd, "Core HwndWrapper..ctor"); 
#endif 
        }
 
        /// 
        ///     Critical: Uses critical member _hwndList
        /// 
        [SecurityCritical] 
        internal static void UnhookHwndSubclass(HwndSubclass subclass)
        { 
            // if exiting the AppDomain, ignore this call.  This avoids changing 
            // the list during the loop in OnAppDomainProcessExit
            if (_exiting) 
                return;

            lock (_hwndList)
            { 
                _hwndList.Remove(subclass);
            } 
        } 

        /// 
        ///     Critical performs an elevation to call HookUpDefWindowProc.
        ///     TreatAsSafe - net effect of this is to remove our already registered WndProc's on domain shutdown.
        ///                          safe - as you had to elevate to add these already. Removing them is considered safe.
        /// 
        [SecurityCritical, SecurityTreatAsSafe]
        private static void OnAppDomainProcessExit(object sender, EventArgs e) 
        { 
            // AppDomain is exiting -- if anyone tries to call back into managed code
            // after this point, bad things will happen.  We must remove all unmanaged 
            // code references to our WndProc delegates.  USER will explode if we set the
            // WndProc to null, so the next most reasonable thing we can do is hook up
            // the DefaultWindowProc.
            //DbgUserBreakPoint(); 

            _exiting = true; 
 
            lock (_hwndList)
            { 
                new SecurityPermission(SecurityPermissionFlag.UnmanagedCode).Assert(); // BlessedAssert:
                try
                {
                    foreach (DictionaryEntry entry in _hwndList) 
                    {
                        IntPtr hwnd = (IntPtr)entry.Value; 
 
                        // tell all the HwndSubclass WndProcs on this window's chain
                        // to detach themselves 
                        UnsafeNativeMethods.SendMessage(hwnd, HwndSubclass.DetachMessage,
                                                            IntPtr.Zero /* wildcard */,
                                                            (IntPtr) 2 /* force and forward */);
 
                        // the last WndProc on the chain might be managed as well
                        // (see HwndSubclass.SubclassWndProc for explanation). 
                        // Just in case, restore the DefaultWindowProc. 
                        HookUpDefWindowProc(hwnd);
                    } 
                }
                finally
                {
                    CodeAccessPermission.RevertAssert(); 
                }
 
            } 
        }
 
        /// 
        ///  TreatAsSafe:  Demands for unmanaged code
        ///  Critical: Elevates by calling an unverifieds UnsafeNativeMethod call
        /// 
        [SecurityTreatAsSafe, SecurityCritical]
        private static void HookUpDefWindowProc(IntPtr hwnd) 
        { 

            SecurityHelper.DemandUnmanagedCode(); 

#if LOGGING
            LogFinishHWND(hwnd, "Core HookUpDWP");
#endif 

            IntPtr result = IntPtr.Zero ; 
 
            // We've already cleaned up, return immediately.
            if (hwnd == IntPtr.Zero) 
            {
                return;
            }
 
            IntPtr defWindowProc = GetDefWindowProcAddress(hwnd);
 
            if (defWindowProc != IntPtr.Zero) 
            {
                try 
                {
                    result = UnsafeNativeMethods.SetWindowLong(new HandleRef(null,hwnd), NativeMethods.GWL_WNDPROC, defWindowProc);

                } 
                catch(System.ComponentModel.Win32Exception e)
                { 
                    // We failed to change the window proc.  Now what? 

                    if (e.NativeErrorCode != 1400) // ERROR_INVALID_WINDOW_HANDLE 
                    {
                        // For debugging purposes, throw an exception so we can debug
                        // this and know if it's possible to call SetWindowLong on
                        // the wrong thread. 
                        throw;
                    } 
                } 
                if (result != IntPtr.Zero )
                { 
                    UnsafeNativeMethods.PostMessage(new HandleRef(null,hwnd), NativeMethods.WM_CLOSE, IntPtr.Zero, IntPtr.Zero);
                }
            }
        } 

        // Get the DWP for the given HWND -- returns DefWindowProcA or DefWindowProcW 
        // depending on IsWindowUnicode(hwnd). 
        private static IntPtr GetDefWindowProcAddress(IntPtr hwnd)
        { 
            // We need to swap back in the DefWindowProc, but which one we use depends on
            // what the Unicode-ness of the window.
            if (SafeNativeMethods.IsWindowUnicode(new HandleRef(null,hwnd)))
            { 
                if (_cachedDefWindowProcW == IntPtr.Zero)
                { 
                    _cachedDefWindowProcW = GetUser32ProcAddress("DefWindowProcW"); 
                }
 
                return _cachedDefWindowProcW;
            }
            else
            { 
                if (_cachedDefWindowProcA == IntPtr.Zero)
                { 
                    _cachedDefWindowProcA = GetUser32ProcAddress("DefWindowProcA") ; 
                }
 
                return _cachedDefWindowProcA;
            }
        }
 
        ///
        ///  SecurityCritical: elevates via a call to unsafe native methods 
        ///  SecurityTreatAsSafe: Demands unmgd code permission via SecurityHelper 
        ///
        [SecurityCritical, SecurityTreatAsSafe] 
        private static IntPtr GetUser32ProcAddress(string export)
        {

            SecurityHelper.DemandUnmanagedCode(); 
            IntPtr hModule = UnsafeNativeMethods.GetModuleHandle(ExternDll.User32);
 
 
            if (hModule != IntPtr.Zero)
            { 
                return UnsafeNativeMethods.GetProcAddress(new HandleRef(null, hModule), export);

            }
            return IntPtr.Zero; 
        }
 
#if LOGGING 
        [DllImport("ntdll.dll")]
        private static extern void DbgUserBreakPoint(); 

        [DllImport("ntdll.dll")]
        private static extern void DbgPrint(string msg);
 
        internal static void LogStartHWND(IntPtr hwnd, string fromWhere)
        { 
            string msg = String.Format("BEGIN: {0:X} -- Setting DWP, process = {1} ({2}) {3}", 
                   hwnd,
                   System.Diagnostics.Process.GetCurrentProcess().ProcessName, 
                   fromWhere,
                   System.Environment.NewLine);

            Log(msg); 
        }
 
        internal static void LogFinishHWND(IntPtr hwnd, string fromWhere) 
        {
            string msg = String.Format("END:   {0:X} -- Setting DWP, process = {1} ({2}) {3}", 
                   hwnd,
                   System.Diagnostics.Process.GetCurrentProcess().ProcessName,
                   fromWhere,
                   System.Environment.NewLine); 

            Log(msg); 
        } 

        private static void Log(string msg) 
        {
            //DbgUserBreakPoint();
            /*
            byte[] msgBytes = System.Text.Encoding.ASCII.GetBytes(msg); 
            System.IO.FileStream fs = System.IO.File.Open("c:\\dwplog.txt", System.IO.FileMode.Append, System.IO.FileAccess.Write, System.IO.FileShare.ReadWrite);
 
            fs.Write(msgBytes, 0, msgBytes.Length); 
            fs.Flush();
            fs.Close(); 
            */
        }

#endif 

        private static IntPtr _cachedDefWindowProcA = IntPtr.Zero; 
        private static IntPtr _cachedDefWindowProcW = IntPtr.Zero; 

        /// 
        ///     Critical - used as input to unsafe calls
        ///
        [SecurityCritical]
        private static Hashtable _hwndList = new Hashtable(10); 
        private static bool _exiting = false;
    } 
} 

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
// Copyright (c) Microsoft Corporation. All rights reserved.
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