Code:
/ 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / wpf / src / Core / CSharp / MS / Internal / Automation / EventPropertyMap.cs / 1305600 / EventPropertyMap.cs
//---------------------------------------------------------------------------- // //// Copyright (C) Microsoft Corporation. All rights reserved. // // // // Description: // Accessibility event map classes are used to determine if, and how many // listeners there are for events and property changes. // // History: // 07/23/2003 : BrendanM Ported to WCP // //--------------------------------------------------------------------------- using System; using System.Collections; using System.Windows; using System.Diagnostics; namespace MS.Internal.Automation { // Manages the property map that is used to determine if there are // Automation clients interested in properties. internal class EventPropertyMap { //----------------------------------------------------- // // Constructors // //----------------------------------------------------- #region Constructors // static class, private ctor to prevent creation private EventPropertyMap() { } #endregion Constructors //------------------------------------------------------ // // Internal Methods // //----------------------------------------------------- #region Internal Methods // Called during queueing of property change events to check if there are any // listeners that are interested in this property. Returns true if there are // else false. This function could be called frequently; it must be fast. internal static bool IsInterestingDP(DependencyProperty dp) { using (_propertyLock.ReadLock) { if (_propertyTable != null && _propertyTable.ContainsKey(dp)) { return true; } } return false; } // Updates the list of DynamicProperties that are currently being listened to. // Called by AccEvent class when certain events are added. // // Returns: true if the event property map was created during this call and // false if the property map was not created during this call. internal static bool AddPropertyNotify(DependencyProperty [] properties) { if (properties == null) return false; bool createdMap = false; using (_propertyLock.WriteLock) { // If it doesn't exist, create the property map (key=dp value=listener count) if (_propertyTable == null) { // Up to 20 properties before resize and // small load factor optimizes for speed _propertyTable = new Hashtable(20, .1f); createdMap = true; } int cDPStart = _propertyTable.Count; // properties is an array of the properties one listener is interested in foreach (DependencyProperty dp in properties) { if (dp == null) continue; int cDP = 0; // If the property is in the table, increment it's count if (_propertyTable.ContainsKey(dp)) { cDP = (int)_propertyTable[dp]; } cDP++; _propertyTable[dp] = cDP; } } return createdMap; } // Updates the list of DynamicProperties that are currently being listened to. // Called by AccEvent class when removing certain events. // Returns: true if the property table is empty after this operation. internal static bool RemovePropertyNotify(DependencyProperty [] properties) { Debug.Assert(properties != null); bool isEmpty = false; using (_propertyLock.WriteLock) { if (_propertyTable != null) { int cDPStart = _propertyTable.Count; // properties is an array of the properties one listener is no longer interested in foreach (DependencyProperty dp in properties) { if (_propertyTable.ContainsKey(dp)) { int cDP = (int)_propertyTable[dp]; // Update or remove the entry based on remaining listeners cDP--; if (cDP > 0) { _propertyTable[dp] = cDP; } else { _propertyTable.Remove(dp); } } } // If there are no more properties in the map then delete it; the idea is if there // are no listeners, don't make the property system do extra work. if (_propertyTable.Count == 0) { _propertyTable = null; } } isEmpty = (_propertyTable == null); } return isEmpty; } #endregion Internal Methods //------------------------------------------------------ // // Private Fields // //------------------------------------------------------ #region Private Fields // static class, no instance data... private static ReaderWriterLockWrapper _propertyLock = new ReaderWriterLockWrapper(); private static Hashtable _propertyTable; // key=DP, data=listener count #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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