/// <summary>
/// Callback from DescendentsWalker before the nodes children are visited.
/// </summary>
/// <param name="dependencyObject">node to visit</param>
/// <param name="data">data used for the current tree walk</param>
/// <returns>returns whether or not the children should be visited</returns>
private bool PreVisit(DependencyObject dependencyObject, ProcessingTreeState data, bool visitedViaVisualTree)
{
Debug.Assert(data != null, "dataBlob is either null or not of ProcessingTreeState type");
bool calledProcessAnnotations = false;
SubTreeProcessor processor = GetSubTreeProcessor(dependencyObject);
Debug.Assert(processor != null, "SubtreeProcessor can not be null"); // There is always a default processor
IList<IAttachedAnnotation> attachedAnnotations = processor.PreProcessNode(dependencyObject, out calledProcessAnnotations);
if (attachedAnnotations != null)
data.AttachedAnnotations.AddRange(attachedAnnotations);
// Combine whether this processor called ProcessAnnotations with the info of its siblings
data.CalledProcessAnnotations = data.CalledProcessAnnotations || calledProcessAnnotations;
data.Push();
// Returning true here prevents children from being called
return !calledProcessAnnotations;
}
/// <summary>
/// Callback from DescendentsWalker after the nodes children are visited.
/// </summary>
/// <param name="dependencyObject">node to visit</param>
/// <param name="data">data used for the current tree walk</param>
/// <returns>return value is ignored</returns>
private bool PostVisit(DependencyObject dependencyObject, ProcessingTreeState data, bool visitedViaVisualTree)
{
Debug.Assert(data != null, "dataBlob is either null or not of ProcessingTreeState type");
bool childrenCalledProcessAnnotations = data.Pop();
SubTreeProcessor processor = GetSubTreeProcessor(dependencyObject);
Debug.Assert(processor != null, "SubtreeProcessor can not be null");
bool calledProcessAnnotations = false;
IList<IAttachedAnnotation> attachedAnnotations = processor.PostProcessNode(dependencyObject, childrenCalledProcessAnnotations, out calledProcessAnnotations);
if (attachedAnnotations != null)
data.AttachedAnnotations.AddRange(attachedAnnotations);
// This flag is information available to PostVisit calls
data.CalledProcessAnnotations = data.CalledProcessAnnotations || calledProcessAnnotations || childrenCalledProcessAnnotations;
// This return value is not used by PrePostDescendentsWalker
return true;
}
//------------------------------------------------------
//
// Internal Methods
//
//------------------------------------------------------
#region Internal Methods
/// <summary>
/// Traverse the element tree starting at subtree and load
/// annotations for that subtree.
/// </summary>
/// <param name="subTree">root of the subtree for which to load annotations</param>
/// <returns>list of IAttachedAnnotations that were loaded for 'node';
/// the list will never be null but may be empty</returns>
/// <exception cref="ArgumentNullException">subtree is null</exception>
internal IList<IAttachedAnnotation> ProcessSubTree(DependencyObject subTree)
{
if (subTree == null)
throw new ArgumentNullException("subTree");
ProcessingTreeState data = new ProcessingTreeState();
PrePostDescendentsWalker<ProcessingTreeState> walker = new PrePostDescendentsWalker<ProcessingTreeState>(TreeWalkPriority.VisualTree, PreVisit, PostVisit, data);
walker.StartWalk(subTree);
return data.AttachedAnnotations;
}
