Accessible.cs source code in C# .NET

                        Code:
                         / 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / wpf / src / UIAutomation / UIAutomationClient / MS / Internal / Automation / Accessible.cs / 1305600 / Accessible.cs
                        
                        
                            //---------------------------------------------------------------------------- 
//
// 
//    Copyright (C) Microsoft Corporation.  All rights reserved.
//  
//
// 
// Description: Wraps some of IAccessible to support Focus and top-level window creates 
//
// History: 
//  06/02/2003 : BrendanM Ported to WCP
//
//---------------------------------------------------------------------------
 
using System.Windows.Automation;
using System; 
using Accessibility; 
using System.Text;
using System.Diagnostics; 
using MS.Win32;

// PRESHARP: In order to avoid generating warnings about unkown message numbers and unknown pragmas.
#pragma warning disable 1634, 1691 

namespace MS.Internal.Automation 
{ 
    internal class Accessible
    { 
        internal Accessible(IAccessible acc, object child)
        {
            Debug.Assert(acc != null, "null IAccessible");
            _acc = acc; 
            _child = child;
        } 
 
        // Create an Accessible object; may return null
        internal static Accessible Create( IntPtr hwnd, int idObject, int idChild ) 
        {
            IAccessible acc = null;
            object child = null;
            if( UnsafeNativeMethods.AccessibleObjectFromEvent( hwnd, idObject, idChild, ref acc, ref child ) != 0 /*S_OK*/ || acc == null ) 
                return null;
 
            // Per SDK must use the ppacc and pvarChild from AccessibleObjectFromEvent 
            // to access information about this UI element.
            return new Accessible( acc, child ); 
        }

        internal int State
        { 
            get
            { 
                try 
                {
                    return (int)_acc.get_accState(_child); 
                }
                catch (Exception e)
                {
                    if (IsCriticalMSAAException(e)) 
                        // PRESHARP will flag this as a warning 56503/6503: Property get methods should not throw exceptions
                        // Since this Property is internal, we CAN throw an exception 
#pragma warning suppress 6503 
                        throw;
 
                    return UnsafeNativeMethods.STATE_SYSTEM_UNAVAILABLE;
                }
            }
        } 

        internal IntPtr Window 
        { 
            get
            { 
                if (_hwnd == IntPtr.Zero)
                {
                    try
                    { 
                        if (UnsafeNativeMethods.WindowFromAccessibleObject(_acc, ref _hwnd) != 0/*S_OK*/)
                        { 
                            _hwnd = IntPtr.Zero; 
                        }
                    } 
                    catch( Exception e )
                    {
                        if (IsCriticalMSAAException(e))
                            // PRESHARP will flag this as a warning 56503/6503: Property get methods should not throw exceptions 
                            // Since this Property is internal, we CAN throw an exception
#pragma warning suppress 6503 
                            throw; 

                        _hwnd = IntPtr.Zero; 
                    }
                }
                return _hwnd;
            } 
        }
 
        // miscellaneous functions used with Accessible 

        internal static bool CompareClass(IntPtr hwnd, string szClass) 
        {
            return ProxyManager.GetClassName(NativeMethods.HWND.Cast(hwnd)) == szClass;
        }
 
        internal static bool IsComboDropdown(IntPtr hwnd)
        { 
            return CompareClass(hwnd, "ComboLBox"); 
        }
 
        internal static bool IsStatic(IntPtr hwnd)
        {
            return CompareClass(hwnd, "Static");
        } 

        private bool IsCriticalMSAAException(Exception e) 
        { 
            // Some OLEACC proxies produce out-of-memory for non-critical reasons:
            // notably, the treeview proxy will raise this if the target HWND no longer exists, 
            // GetWindowThreadProcessID fails and it therefore won't be able to allocate shared
            // memory in the target process, so it incorrectly assumes OOM.
            // Some Native impls (media player) return E_POINTER, which COM Interop translates
            // into NullRefException; need to ignore those too. 
            // should ignore those
            return !(e is OutOfMemoryException) 
                && !(e is NullReferenceException) 
                && Misc.IsCriticalException(e);
        } 
        private IntPtr _hwnd;
        private IAccessible _acc;
        private Object _child;
    } 
}

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
// Copyright (c) Microsoft Corporation. All rights reserved.
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Accessible.cs source code in C# .NET

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