// Helper method that performs a recursive, depth-first search of children starting at the specified parent,
// looking for any children that conform to the specified Type and are marked with a SelectionStop
//
private static T FindChildSelectionStop <T>(DependencyObject parent, int leftIndex, int rightIndex, SearchDirection iterationDirection, int maxDepth, MatchDirection matchDirection)
where T : DependencyObject
{
if (parent == null || maxDepth <= 0)
{
return(null);
}
int step = iterationDirection == SearchDirection.Next ? 1 : -1;
int index = iterationDirection == SearchDirection.Next ? leftIndex : rightIndex;
for (; index >= leftIndex && index <= rightIndex; index = index + step)
{
DependencyObject child = VisualTreeHelper.GetChild(parent, index);
// If MatchDirection is set to Down, do an eligibility match BEFORE we dive down into
// more children.
//
if (matchDirection == MatchDirection.Down && IsEligibleSelectionStop <T>(child))
{
return((T)child);
}
// If this child is not an eligible SelectionStop because it is not visible,
// there is no point digging down to get to more children.
//
if (!VisualTreeUtils.IsVisible(child as UIElement))
{
continue;
}
int grandChildrenCount = VisualTreeHelper.GetChildrenCount(child);
if (grandChildrenCount > 0 && IsExpanded(child))
{
T element = FindChildSelectionStop <T>(child, 0, grandChildrenCount - 1, iterationDirection, maxDepth - 1, matchDirection);
if (element != null)
{
return(element);
}
}
// If MatchDirection is set to Up, do an eligibility match AFTER we tried diving into
// more children and failed to find something we could return.
//
if (matchDirection == MatchDirection.Up && IsEligibleSelectionStop <T>(child))
{
return((T)child);
}
}
return(null);
}
// Helper method used from GetNeighborSelectionStop()
// Returns a parent DependencyObject of the specified element that is
//
// * Visible AND
// * ( Marked with a SelectionStop OR
// * Marked with IsSelectionScope = true OR
// * Has more than one child )
//
private static DependencyObject GetEligibleParent(DependencyObject element, out int childIndex, out int childrenCount, out int childDepth, out bool isSelectionStop, out bool isSelectionScope)
{
childDepth = 0;
isSelectionStop = false;
isSelectionScope = false;
bool isVisible;
do
{
element = VisualTreeUtils.GetIndexedVisualParent(element, out childrenCount, out childIndex);
isSelectionStop = element == null ? false : (GetSelectionStop(element) != null);
isSelectionScope = element == null ? false : GetIsSelectionScope(element);
isVisible = VisualTreeUtils.IsVisible(element as UIElement);
childDepth++;
}while (
element != null &&
(isVisible == false ||
(isSelectionStop == false &&
isSelectionScope == false &&
childrenCount < 2)));
return(element);
}
// Helper method that return true if the given element is marked with a SelectionStop,
// if it derives from the specified Type, and if it is Visible (assuming it derives from UIElement)
//
private static bool IsEligibleSelectionStop <T>(DependencyObject element) where T : DependencyObject
{
return((GetSelectionStop(element) != null) && typeof(T).IsAssignableFrom(element.GetType()) && VisualTreeUtils.IsVisible(element as UIElement));
}
