FrameworkContextData.cs source code in C# .NET

Source code for the .NET framework in C#

                        
Code:

                         / 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / wpf / src / Framework / System / Windows / FrameworkContextData.cs / 1305600 / FrameworkContextData.cs
                        

                        
                             
using System.Windows.Threading;

using MS.Utility;
 
using System;
using System.Collections.Generic; 
using System.Diagnostics; 

namespace System.Windows 
{
    internal class FrameworkContextData
    {
        public static FrameworkContextData From(Dispatcher context) 
        {
            FrameworkContextData data = (FrameworkContextData)context.Reserved2; 
 
            if (data == null)
            { 
                data = new FrameworkContextData();
                context.Reserved2 = data;
            }
 
            return data;
        } 
 
        // Enforce never creating except via static constructor above.
        private FrameworkContextData() 
        {
        }

        // 
        // Property Invalidation of Inheritable Properties
        // 
        // At the context level, we need to keep track of all inheritable property invalidations currently 
        // in action.  The reason that there can be multiple invalidations going on at the same time is because
        // an invalidation of one property can cause an invalidation of a different property.  The result is that 
        // the first invalidation *pauses* while the second invalidation is delivered to the tree.
        //
        // We keep track of these invalidations to be able to optimize a recursion of the same property
        // invalidation from an element to that element's children.  FrameworkElement.InvalidateTree will 
        // check the stack of walkers here and, if it finds a match, will conclude that a new DescendentsWalker
        // need not be spun up.  And there was much rejoicing. 
        // 

        public void AddWalker(object data, DescendentsWalkerBase walker) 
        {
            // push a new walker on the top of the stack
            WalkerEntry walkerEntry = new WalkerEntry();
            walkerEntry.Data = data; 
            walkerEntry.Walker = walker;
 
            _currentWalkers.Add(walkerEntry); 
        }
 
        public void RemoveWalker(object data, DescendentsWalkerBase walker)
        {
            // pop the walker off the top of the stack
            int last = _currentWalkers.Count - 1; 
#if DEBUG
            WalkerEntry walkerEntry = _currentWalkers[last]; 
 
            Debug.Assert((walkerEntry.Data == data) && (walkerEntry.Walker == walker),
                "Inheritance DescendentsWalker tracker removal failed"); 
#endif
            _currentWalkers.RemoveAt(last);
        }
 
        public bool WasNodeVisited(DependencyObject d, object data)
        { 
            // check to see if the given property on the given object is going to be visited by the 
            // DescendentsWalker on the top of the stack
            if (_currentWalkers.Count > 0) 
            {
                int last = _currentWalkers.Count - 1;

                WalkerEntry walkerEntry = _currentWalkers[last]; 

                if (walkerEntry.Data == data) 
                { 
                    return walkerEntry.Walker.WasVisited(d);
                } 
            }

            return false;
        } 

        private struct WalkerEntry 
        { 
            public object Data; // either the inheritable DP being invalidated, or the AncestorChangedDelegate, or the ResourceChangedDelegate
            public DescendentsWalkerBase Walker; 
        }

        private List _currentWalkers = new List(4);
    } 
}
 

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

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