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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: Lightweight class to wrap Win32 WinEvents.
// PRESHARP: In order to avoid generating warnings about unkown message numbers and unknown pragmas.
#pragma warning disable 1634, 1691
using System;
using System.Collections;
using System.Runtime.InteropServices;
using System.ComponentModel;
using System.Diagnostics;
using MS.Win32;
namespace MS.Internal.Automation
{
// Lightweight class to wrap Win32 WinEvents. Users of this class would
// inherit from WinEventWrap do the following:
// 1. Call the base constructor with a params array of event identifiers
// 2. Override WinEventProc to provide an implementation.
internal class WinEventWrap
{
//------------------------------------------------------
//
// Constructors
//
//------------------------------------------------------
#region Constructors
// ctor that takes an array of events
internal WinEventWrap(int [] eventIds)
{
Debug.Assert(eventIds != null && eventIds.Length > 0, "eventIds is invalid");
_eventIds = (int [])eventIds.Clone();
_hHooks = new IntPtr[_eventIds.Length];
Init();
}
~WinEventWrap()
{
Clear();
}
#endregion Constructors
//------------------------------------------------------
//
// Internal Methods
//
//------------------------------------------------------
#region Internal Methods
internal virtual void WinEventProc(int eventId, IntPtr hwnd, int idObject, int idChild, uint eventTime)
{
// override this to provide an implementation
}
internal void Clear()
{
StopListening();
lock(this)
{
_clientCallbacks.Clear ();
}
if (_gchThis.IsAllocated)
{
_gchThis.Free();
}
}
internal void AddCallback(object clientCallback)
{
lock (this)
{
_clientCallbacks.Add(clientCallback);
}
}
internal bool RemoveCallback(object clientCallback)
{
if (clientCallback == null)
return true; // temp until cleanup of WinEvent code is complete
bool listIsEmpty = true;
lock (this)
{
if (_clientCallbacks.Count == 0)
return true;
// remove a specific callback
_clientCallbacks.Remove(clientCallback);
listIsEmpty = (_clientCallbacks.Count == 0);
}
return listIsEmpty;
}
// install WinEvent hook and start getting the callback.
internal void StartListening()
{
_fBusy = true;
int i = 0;
foreach (int eventId in _eventIds)
{
// There is no indication in the Windows SDK documentation that SetWinEventHook()
// will set an error to be retrieved with GetLastError, so set the pragma to ignore
// the PERSHARP warning.
#pragma warning suppress 6523
_hHooks[i] = UnsafeNativeMethods.SetWinEventHook(eventId, eventId, IntPtr.Zero, _winEventProc, 0, 0, _fFlags);
if (_hHooks[i] == IntPtr.Zero)
{
StopListening();
throw new Win32Exception();
}
i++;
}
_fBusy = false;
}
internal void StopListening()
{
// ASSUMPTION: Before StopListening is called, all callback delegates have been removed
// so that any events received while hooks are being removed become noops (since there's
// no handlers for them to call).
_fBusy = true;
for (int i=0;i<_hHooks.Length;i++)
{
if (_hHooks[i] != IntPtr.Zero)
{
// There is no indication in the Windows SDK documentation that UnhookWinEvent()
// will set an error to be retrieved with GetLastError, so set the pragma to ignore
// the PERSHARP warning.
#pragma warning suppress 6523
UnsafeNativeMethods.UnhookWinEvent(_hHooks[i]);
_hHooks[i] = IntPtr.Zero;
}
}
if (_qEvents != null)
{
_qEvents.Clear();
}
_fBusy = false;
}
// Handlers may make a call to another process so don't want to lock around code that protects _clientCallbacks.
// Instead, grab the callbacks w/in a lock then call them outside of the lock. This technique has potential for
// error if (for instance) handler A could remove both itself and handler B but for now don't need to worry
// about handlers getting out of sync with the ones in the master array because the callbacks are defined w/in
// this code and the handler for new UI doesn't remove itself (or anyone else).
internal object[] GetHandlers()
{
lock (this)
{
object[] handlers = new object[_clientCallbacks.Count];
for (int i = 0; i < _clientCallbacks.Count; i++)
handlers[i] = _clientCallbacks[i];
return handlers;
}
}
#endregion Internal Methods
//------------------------------------------------------
//
// Private Methods
//
//------------------------------------------------------
#region Private Methods
// queue winevents so that the get processed in the order we receive them. If we just
// dispatch them as we get them, we'll end up getting some _while_ we are processing others,
// and end up completing those events out of order, making the event order appear backwards.
// This code checks whether we are currently processing an event, and if so, queues it so that
// we process it when we're done with the current event.
private void WinEventReentrancyFilter(int winEventHook, int eventId, IntPtr hwnd, int idObject, int idChild, int eventThread, uint eventTime)
{
if ( _fBusy )
{
_qEvents.Enqueue(new WinEvent(eventId, hwnd, idObject, idChild, eventTime));
}
else
{
_fBusy = true;
try
{
PreWinEventProc(eventId, hwnd, idObject, idChild, eventTime); // deliver this event
}
catch( Exception e )
{
if( Misc.IsCriticalException( e ) )
throw;
// ignore exceptions for now since we've no way to let clients add exception handlers
}
while (_qEvents.Count > 0)
{
WinEvent e = (WinEvent)_qEvents.Dequeue(); // process queued events
try
{
PreWinEventProc(e._eventId, e._hwnd, e._idObject, e._idChild, e._eventTime);
}
catch( Exception ex )
{
if( Misc.IsCriticalException( ex ) )
throw;
// ignore exceptions for now since we've no way to let clients add exception handlers
}
}
_fBusy = false;
}
}
private void PreWinEventProc(int eventId, IntPtr hwnd, int idObject, int idChild, uint eventTime)
{
// Ignore events from the UIA->MSAA bridge: these are recognizable as having
// >0 idObject, and the target HWND having a UIA impl.
if (idObject > 0)
{
if (UiaCoreApi.UiaHasServerSideProvider(hwnd))
{
// Bridge event - ignore it.
return;
}
}
// 0 is used as a marker value elsewhere, so bump up to 1
if(eventTime == 0)
{
eventTime = 1;
}
WinEventProc(eventId, hwnd, idObject, idChild, eventTime);
}
private void Init()
{
// Keep the garbage collector from moving things around
_winEventProc = new NativeMethods.WinEventProcDef(WinEventReentrancyFilter);
_gchThis = GCHandle.Alloc(_winEventProc);
_clientCallbacks = new ArrayList(2);
_qEvents = new Queue(16, (float)2.0); // (initial cap, growth factor)
_fFlags = NativeMethods.WINEVENT_OUTOFCONTEXT;
}
#endregion Private Methods
//------------------------------------------------------
//
// Private Fields
//
//------------------------------------------------------
#region Private Fields
private class WinEvent
{
internal WinEvent(int eventId, IntPtr hwnd, int idObject, int idChild, uint eventTime)
{
_eventId = eventId;
_hwnd = hwnd;
_idObject = idObject;
_idChild = idChild;
_eventTime = eventTime;
}
public int _eventId;
public IntPtr _hwnd;
public int _idObject;
public int _idChild;
public uint _eventTime;
}
private Queue _qEvents; // Queue of events waiting to be processed
private int [] _eventIds; // the WinEvent(s) this instance is handling
private IntPtr [] _hHooks; // the returned handles(s) from SetWinEventHook
private bool _fBusy; // Flag indicating if we're busy processing
private int _fFlags; // SetWinEventHook flags
private GCHandle _gchThis; // GCHandle to keep GCs from moving this callback
private NativeMethods.WinEventProcDef _winEventProc; // the callback handed to USER for WinEvents
protected ArrayList _clientCallbacks; // the client callback interface objects
#endregion Private Fields
}
}
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