//------------------------------------------------------
//
// 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;
}
