public static DependencyObject?GetDirectionOverride(
DependencyObject element,
DependencyObject?searchRoot,
FocusNavigationDirection direction,
bool ignoreFocusabililty = false)
{
DependencyObject?overrideElement = null;
DependencyProperty?property = GetXYFocusPropertyIndex(element, direction);
if (property != null)
{
overrideElement = element.GetValue(property) as DependencyObject;
if (overrideElement != null && (!ignoreFocusabililty && !XYFocusFocusability.IsValidCandidate(overrideElement)))
{
return(null);
}
// If an override was specified, but it is located outside the searchRoot, don't use it as the candidate.
if (searchRoot != null &&
overrideElement != null &&
searchRoot.IsAncestorOf(overrideElement) == false)
{
return(null);
}
}
return(overrideElement);
}
internal static List <XYFocus.XYFocusParameters> FindElements(
DependencyObject?startRoot,
DependencyObject?currentElement,
DependencyObject?activeScroller,
bool ignoreClipping,
bool shouldConsiderXYFocusKeyboardNavigation)
{
bool isScrolling = (activeScroller != null);
List <XYFocus.XYFocusParameters> focusList = new List <XYFocus.XYFocusParameters>(InitialCandidateListCapacity);
var collection = FocusProperties.GetFocusChildren(startRoot);
if (collection == null) // || collection.IsLeaving())
{
return(focusList);
}
var kidCount = collection.Length;
//Iterate though every node in the tree that is focusable
for (uint i = 0; i < kidCount; i++)
{
DependencyObject child = collection[i];
if (child == null)
{
continue;
}
bool isEngagementEnabledButNotEngaged = FocusProperties.IsFocusEngagementEnabled(child) && !FocusProperties.IsFocusEngaged(child);
//This is an element that can be focused
if (child != currentElement && XYFocusFocusability.IsValidCandidate(child))
{
var parameters = new XYFocus.XYFocusParameters();
if (isScrolling)
{
var scrollCandidate = child;
var bounds = GetBoundsForRanking(scrollCandidate, ignoreClipping);
//Include all elements participating in scrolling or
//elements that are currently not occluded (in view) or
//elements that are currently occluded but part of a parent scrolling surface.
if (IsCandidateParticipatingInScroll(scrollCandidate, activeScroller) ||
!IsOccluded(scrollCandidate, bounds) ||
IsCandidateChildOfAncestorScroller(scrollCandidate, activeScroller))
{
parameters.Element = scrollCandidate;
parameters.Bounds = bounds;
focusList.Add(parameters);
}
}
else
{
var bounds = GetBoundsForRanking(child, ignoreClipping);
parameters.Element = child;
parameters.Bounds = bounds;
focusList.Add(parameters);
}
}
if (IsValidFocusSubtree(child, shouldConsiderXYFocusKeyboardNavigation) && !isEngagementEnabledButNotEngaged)
{
var subFocusList = FindElements(child, currentElement, activeScroller, ignoreClipping, shouldConsiderXYFocusKeyboardNavigation);
focusList.AddRange(subFocusList);
}
}
return(focusList);
}