Code:
/ DotNET / DotNET / 8.0 / untmp / WIN_WINDOWS / lh_tools_devdiv_wpf / Windows / AccessibleTech / longhorn / Automation / UIAutomationClient / MS / Internal / Automation / CacheHelper.cs / 1 / CacheHelper.cs
//---------------------------------------------------------------------------- // //// Copyright (C) Microsoft Corporation. All rights reserved. // // // // Description: Static class that manages prefetching and normalization // // History: // 03/10/2004 : [....] Created // //--------------------------------------------------------------------------- using System; using System.Diagnostics; using System.Windows; using System.Windows.Automation; using System.Windows.Automation.Provider; using System.ComponentModel; using MS.Win32; // For methods that support prefetching, ClientAPI sends the UiaCoreApi // a cacherequest that lists the relatives of the element (TreeScope) // and properties/patterns to return. The API returns with a CacheResponse // with all this information "flattened out" - this class has the task // of inflating that response into a tree of AutomationElements. // // The response consists of two parts: // A 2-D array of property values: // There is one row for every element (usually just the target element // itself, but can also include rows for children and descendants if // TreeScope was used). // Each row then consists of: // - a value that is the hnode for the element (unless AutomationElementMode // is empty, in which case this slot is null). // - values for the requested properties // - values for the requetsed patterns // // The values in the 2-D array are Variant-based objects when we get them // back from the unmanaged API - we immediately convert them to the appropriate // CLR type before we use that array - this conversion is done in the CacheResponse // ctor in UiaCoreApis. This conversion, for example: // converts ints to appropriate enums // converts int[]s to Rects for BoundingRectangle // converts the inital object representing the hnode to a SafeHandle // converts objects representing hpatterns to SafeHandles. // // The second part of the response is a string describing the tree structure // - this is a lisp-like tree description, and it describes a traversal // of the tree - a '(' every time a node is entered, and a ')' every time // a node is left. // A simple tree consisting of a single node with two children would be // represented by the string "(()())". // The AutomationElement tree structure can be determined by parsing this // string. // // This string is modified slightly from the description above - if a node // in the tree also has a row of properties in the table - which is the // usual case - then the '(' is replaced with a 'P'. The rows in the table // are stored in "preorder traversal order", so they can easily be matched // up with successive 'P's from the tree description string. namespace MS.Internal.Automation { static class CacheHelper { //----------------------------------------------------- // // Internal Methods // //----------------------------------------------------- #region Internal Methods internal static AutomationElement BuildAutomationElementsFromResponse( UiaCoreApi.UiaCacheRequest cacheRequest, UiaCoreApi.UiaCacheResponse response) { if (response.TreeStructure == null) { Debug.Assert(response.RequestedData == null, "both RequestedData and TreeStructure should be null or non-null"); return null; } // FrozenCacheRequest should not be null one new AE code, but may // still be null on old code paths - eg. top level window events - where // prefetching is not yet enabled. if (cacheRequest == null) { cacheRequest = CacheRequest.DefaultUiaCacheRequest; } // ParseTreeDescription is the method that parses the returned data // and builds up the tree, setting properties on each node as it goes along... // index and propIndex keep track of where it is, and we check afterwards // that all are pointing to the end, to ensure that everything matched // up as expected. int index = 0; int propIndex = 0; bool askedForChildren = (cacheRequest.TreeScope & TreeScope.Children) != 0; bool askedForDescendants = (cacheRequest.TreeScope & TreeScope.Descendants) != 0; AutomationElement root = ParseTreeDescription(response.TreeStructure, response.RequestedData, ref index, ref propIndex, cacheRequest, askedForChildren, askedForDescendants); if (index != response.TreeStructure.Length) { Debug.Assert(false, "Internal error: got malformed tree description string (extra chars at end)"); return null; } if (response.RequestedData != null && propIndex != response.RequestedData.GetLength(0)) { Debug.Assert(false, "Internal error: mismatch between count of property buckets and nodes claiming them"); return null; } // Properties are wrapped (eg. pattern classes inserted in front of interface) as // they are being returned to the caller, in the AutomationElement accessors, not here. return root; } #endregion Internal Methods //------------------------------------------------------ // // Private Methods // //----------------------------------------------------- #region Private Methods // Parses the string as returned from ElementSearcher - see ElementSearcher.cs // for a description of the format string. Summary is that it is a lisp-like // set of parens indicating tree structure (eg. "(()())" indicates a node containing // two child nodes), but uses 'P' instead of an open paran to indicate that the // corresonding node has a property array that needs to be associated with it. // // index is the current position in the tree strucure string, // propIndex is the current position in the array of property arrays // (an array of properties returned for each element that matches the // condition specified in the Searcher condition.) private static AutomationElement ParseTreeDescription( string treeDescription, object[,] properties, ref int index, ref int propIndex, UiaCoreApi.UiaCacheRequest cacheRequest, bool askedForChildren, bool askedForDescendants ) { // Check that this is a 'begin node' tag (with or without properties)... if (string.IsNullOrEmpty(treeDescription)) return null; char c = treeDescription[index]; if (c != '(' && c != 'P') { return null; } bool havePropertiesForThisNode = c == 'P'; index++; SafeNodeHandle hnode = null; // If we have information for this node, and we want full remote // references back, then extract the hnode from the first slot of that // element's property row... if (havePropertiesForThisNode && cacheRequest.AutomationElementMode == AutomationElementMode.Full) { hnode = (SafeNodeHandle)properties[propIndex, 0]; } // Attach properties if present... object[,] cachedValues = null; int cachedValueIndex = 0; if (havePropertiesForThisNode) { cachedValues = properties; cachedValueIndex = propIndex; propIndex++; } AutomationElement node = new AutomationElement(hnode, cachedValues, cachedValueIndex, cacheRequest); if( askedForChildren || askedForDescendants ) { // If we did request children or descendants at this level, then set the // cached first child to null - it may get overwritten with // an actual value later; but the key thing is that it gets // set so we can distinguish the "asked, but doesn't have one" from // the "didn't ask" case. (Internally, AutomationElement uses // 'this' to indicate the later case, and throws an exception if // you ask for the children without having previously asked // for them in a CacheRequest.) node.SetCachedFirstChild(null); } // Add in children... AutomationElement prevChild = null; for (; ; ) { // Recursively parse the string... AutomationElement child = ParseTreeDescription( treeDescription, properties, ref index, ref propIndex, cacheRequest, askedForDescendants, askedForDescendants); if (child == null) break; // Then link child node into tree... child.SetCachedParent(node); if (prevChild == null) { node.SetCachedFirstChild(child); } else { prevChild.SetCachedNextSibling(child); } prevChild = child; } // Ensure that end node tag is present... if (treeDescription[index] != ')') { Debug.Assert(false, "Internal error: Got malformed tree description string, missing closing paren"); return null; } index++; return node; } #endregion Private Methods //------------------------------------------------------ // // Private Fields // //------------------------------------------------------ #region Private Fields // Static class - no private fields #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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