EventListenerClientSide.cs source code in C# .NET

                        Code:
                         / DotNET / DotNET / 8.0 / untmp / WIN_WINDOWS / lh_tools_devdiv_wpf / Windows / AccessibleTech / longhorn / Automation / UIAutomationClient / MS / Internal / Automation / EventListenerClientSide.cs / 1 / EventListenerClientSide.cs
                        
                        
                            //---------------------------------------------------------------------------- 
//
// 
//    Copyright (C) Microsoft Corporation.  All rights reserved.
//  
//
// 
// Description: This class wraps an event listener object on the client side. 
//
// History: 
//  06/17/2003 : [....] Ported to WCP
//
//---------------------------------------------------------------------------
 
using System;
using System.Diagnostics; 
using System.Windows.Automation; 
using System.ComponentModel;    // needed by AsyncOperation
using System.Runtime.InteropServices; 
using MS.Win32;

namespace MS.Internal.Automation
{ 
    // This class wraps an event listener object on the client side.
    internal class EventListenerClientSide : MarshalByRefObject 
    { 
        //-----------------------------------------------------
        // 
        //  Constructors
        //
        //-----------------------------------------------------
 
        #region Constructors
 
        internal EventListenerClientSide(AutomationElement elRoot, Delegate clientCallback, EventListener l) 
        {
            _eventListener = l; 
            _refElement = elRoot;
            // Ensure that RuntimeId is cached on elRoot so that later compares can be done w/o accessing the native element
            _refRid = elRoot.GetRuntimeId();
            _clientCallback = clientCallback; 
            _callbackDelegate = new UiaCoreApi.UiaEventCallback(OnEvent);
            _gch = GCHandle.Alloc(_callbackDelegate); 
 
            //
 



 
        }
 
        #endregion Constructors 

        //------------------------------------------------------ 
        //
        //  Internal Methods
        //
        //----------------------------------------------------- 

        #region Internal Methods 
 
        // Unmanaged DLL calls back on this to notify a UIAccess client of an event.
        internal void OnEvent(IntPtr argsAddr, object[,] requestedData, string treeStructure) 
        {
            AutomationEventArgs e = UiaCoreApi.GetUiaEventArgs(argsAddr);
            if (e.EventId == AutomationElement.AutomationFocusChangedEvent)
            { 
                uint eventTime = SafeNativeMethods.GetTickCount();
                if (eventTime == 0) // 0 is used as a marker value, so bump up to 1 if we get it. 
                    eventTime = 1; 

                // There's no FocusChangedEventArgs in core, but clients expect one, so substitute if needed... 
                // (otherwise the cast in InvokeHandlers will fail...)
                e = new InternalAutomationFocusChangedEventArgs(0, 0, eventTime);
            }
            UiaCoreApi.UiaCacheResponse cacheResponse = new UiaCoreApi.UiaCacheResponse(requestedData, treeStructure, _eventListener.CacheRequest); 
            // Invoke the listener's callback but not on this thread.  Queuing this onto a worker thread allows
            // OnEvent to return (which allows the call on the server-side to complete) and avoids a deadlock 
            // situation when the client accesses properties on the source element. 
            ClientEventManager.CBQ.PostWorkItem(new CalloutQueueItem(_clientCallback, cacheResponse, e, _eventListener.CacheRequest));
        } 


        // IsListeningFor - called by UIAccess client during removal of listeners. Returns
        // true if rid, eventId and clientCallback represent this listener instance. 
        internal bool IsListeningFor(AutomationEvent eventId, AutomationElement el, Delegate clientCallback)
        { 
            // Removing the event handler using the element RuntimeId prevents problems with dead elements 
            int[] rid = null;
            try 
            {
                rid = el.GetRuntimeId();
            }
            catch( ElementNotAvailableException ) 
            {
                // This can't be the element this instance is holding because when 
                // creating this instance we caused the RuntimeId to be cached. 
                return false;
            } 

            if( !Misc.Compare( _refRid, rid ) )
                return false;
 
            if( _eventListener.EventId != eventId )
                return false; 
 
            if (_clientCallback != clientCallback)
                return false; 

            return true;
        }
 
        // WithinScope - returns true if el is within the scope of this listener.
        internal bool WithinScope(AutomationElement el) 
        { 
            // Quick look: If want all elements then no compare is necessary
            if ((_eventListener.TreeScope & TreeScope.Subtree) == TreeScope.Subtree && 
                 Misc.Compare(_refRid, AutomationElement.RootElement.GetRuntimeId()))
            {
                return true;
            } 

 
            // If our weak reference is still alive, then get it 
            AutomationElement elThis = AutomationElement;
            if (elThis == null) 
            {
                return false;   // reference is no longer alive
            }
 
            // Quick look: If they want this element
            if ((_eventListener.TreeScope & TreeScope.Element) != 0 && Misc.Compare(el, elThis)) 
            { 
                return true;
            } 

            AutomationElement elParent;

            // Quick look (sort of): If they want to include children 
            if (((_eventListener.TreeScope & TreeScope.Children) != 0 || (_eventListener.TreeScope & TreeScope.Descendants) != 0))
            { 
                elParent = TreeWalker.RawViewWalker.GetParent(el); 
                if (elParent != null && Misc.Compare(elParent, elThis))
                    return true; 
            }

            // Quick look (sort of): If they want to include the parent
            if (((_eventListener.TreeScope & TreeScope.Parent) != 0 || (_eventListener.TreeScope & TreeScope.Ancestors) != 0)) 
            {
                elParent = TreeWalker.RawViewWalker.GetParent(elThis); 
                if (elParent != null && Misc.Compare(elParent, el)) 
                    return true;
            } 

            // More work if they want to include any descendents of this element
            if ((_eventListener.TreeScope & TreeScope.Descendants) != 0 && IsChildOf(elThis, el))
            { 
                return true;
            } 
 
            // More work if they want to include any anscestors of this element
            if ((_eventListener.TreeScope & TreeScope.Ancestors) != 0 && IsChildOf(el, elThis)) 
            {
                return true;
            }
 
            return false;
        } 
 
        // WithinScope - returns true if rid is the RuntimeId of this listener or listening for all elements.
        internal bool WithinScope( int [] rid ) 
        {
            // Quick look: If want all elements then no compare is necessary
            if ((_eventListener.TreeScope & TreeScope.Subtree) == TreeScope.Subtree &&
                 Misc.Compare(_refRid, AutomationElement.RootElement.GetRuntimeId())) 
            {
                return true; 
            } 

            // Can only determine if ref element is the element using RuntimeId; 
            // can't determine other relationships.
            if ( ( _eventListener.TreeScope & TreeScope.Element ) == 0 )
            {
                return false; 
            }
 
            // Quick look: If they want this element but use our ref RuntimeId 
            // since the weak reference may be gone.
            if ( Misc.Compare( rid, _refRid ) ) 
            {
                return true;
            }
 
            // rid is not the ref element
            return false; 
        } 
        #endregion Internal Methods
 

        //------------------------------------------------------
        //
        //  Internal Properties 
        //
        //------------------------------------------------------ 
 
        #region Internal Properties
 
        internal EventListener EventListener
        {
            get
            { 
                return _eventListener;
            } 
        } 

        internal Delegate ClientCallback 
        {
            get
            {
                return _clientCallback; 
            }
        } 
 
        internal AutomationElement AutomationElement
        { 
            get
            {
                return _refElement;
            } 
        }
 
        internal UiaCoreApi.UiaEventCallback CallbackDelegate 
        {
            get 
            {
                return _callbackDelegate;
            }
        } 

        internal SafeEventHandle EventHandle 
        { 
            get
            { 
                return _eventHandle;
            }

            set 
            {
                _eventHandle = value; 
            } 
        }
        #endregion Internal Properties 


        //-----------------------------------------------------
        // 
        //  Private Methods
        // 
        //------------------------------------------------------ 

        #region Private Methods 

        // return true if el is a child of elPossibleParent
        private bool IsChildOf(AutomationElement elPossibleParent, AutomationElement el)
        { 
            // Do the work [slower] using the proxies
            if( ! Misc.Compare( el, elPossibleParent ) ) 
            { 
                AutomationElement elPossibleChild = TreeWalker.RawViewWalker.GetParent(el);
                while( elPossibleChild != null ) 
                {
                    if( Misc.Compare( elPossibleChild, elPossibleParent ) )
                    {
                        return true; 
                    }
                    elPossibleChild = TreeWalker.RawViewWalker.GetParent(elPossibleChild); 
                } 
            }
            return false; 
        }

        #endregion Private Methods
 

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

        #region Private Fields
 
        private EventListener _eventListener;
        private AutomationElement _refElement; 
        private int [] _refRid; 
        private Delegate _clientCallback;
        private UiaCoreApi.UiaEventCallback _callbackDelegate; 
        private GCHandle _gch; // GCHandle to keep GCs from moving the callback
        private SafeEventHandle _eventHandle;

        #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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EventListenerClientSide.cs source code in C# .NET

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