void RegisterForCallback()
{
if (!m_registeredForCallback)
{
global::System.Diagnostics.Debug.Assert(m_pendingElements.Count != 0);
m_registeredForCallback = true;
BuildTreeScheduler.RegisterWork(
m_pendingElements[m_pendingElements.Count - 1].VirtInfo.Phase, // Use the phase of the last one in the sorted list
DoPhasedWorkCallback);
}
}
void DoPhasedWorkCallback()
{
MarkCallbackRecieved();
if (m_pendingElements.Count > 0 && !BuildTreeScheduler.ShouldYield())
{
var visibleWindow = m_owner.VisibleWindow;
SortElements(visibleWindow);
int currentIndex = m_pendingElements.Count - 1;
do
{
var info = m_pendingElements[currentIndex];
var element = info.Element;
var virtInfo = info.VirtInfo;
var dataIndex = virtInfo.Index;
int currentPhase = virtInfo.Phase;
if (currentPhase > 0)
{
int nextPhase = VirtualizationInfo.PhaseReachedEnd;
virtInfo.DataTemplateComponent.ProcessBindings(virtInfo.Data, -1 /* item index unused */, currentPhase, out nextPhase);
ValidatePhaseOrdering(currentPhase, nextPhase);
var previousAvailableSize = LayoutInformation.GetAvailableSize(element);
element.Measure(previousAvailableSize);
if (nextPhase > 0)
{
virtInfo.Phase = nextPhase;
// If we are the first item or
// If the current items phase is higher than the next items phase, then move to the next item.
if (currentIndex == 0 ||
virtInfo.Phase > m_pendingElements[currentIndex - 1].VirtInfo.Phase)
{
currentIndex--;
}
}
else
{
m_pendingElements.RemoveAt(currentIndex);
currentIndex--;
}
}
else
{
throw new InvalidOperationException("Cleared element found in pending list which is not expected");
}
var pendingCount = (int)(m_pendingElements.Count);
if (currentIndex == -1)
{
// Reached the top, start from the bottom again
currentIndex = pendingCount - 1;
}
else if (currentIndex > -1 && currentIndex < pendingCount - 1)
{
// If the next element is oustide the visible window and there are elements in the visible window
// go back to the visible window.
bool nextItemIsVisible = SharedHelpers.DoRectsIntersect(visibleWindow, m_pendingElements[currentIndex].VirtInfo.ArrangeBounds);
if (!nextItemIsVisible)
{
bool haveVisibleItems = SharedHelpers.DoRectsIntersect(visibleWindow, m_pendingElements[pendingCount - 1].VirtInfo.ArrangeBounds);
if (haveVisibleItems)
{
currentIndex = pendingCount - 1;
}
}
}
} while (m_pendingElements.Count > 0 && !BuildTreeScheduler.ShouldYield());
}
if (m_pendingElements.Count > 0)
{
RegisterForCallback();
}
}
