protected override Size ArrangeOverride(VirtualizingLayoutContext context, Size finalSize)
{
var realizationRect = context.RealizationRect;
int itemCount = context.ItemCount;
int firstRealizedIndex = FirstRealizedIndexInRect(realizationRect, itemCount);
int lastRealizedIndex = LastRealizedIndexInRect(realizationRect, itemCount);
Debug.WriteLine("Arrange:" + realizationRect.ToString());
// Viewport + Buffer Rect.
for (int currentIndex = firstRealizedIndex; currentIndex <= lastRealizedIndex; currentIndex++)
{
var element = context.GetOrCreateElementAt(currentIndex);
var arrangeRect = new Rect(0, currentIndex * ItemHeight, ItemWidth, ItemHeight);
element.Arrange(arrangeRect);
Debug.WriteLine(" Arrange:" + currentIndex + " :" + arrangeRect);
}
// Anchor
var anchorIndex = context.RecommendedAnchorIndex;
if (anchorIndex >= 0)
{
var anchor = context.GetOrCreateElementAt(anchorIndex);
var arrangeRect = new Rect(0, anchorIndex * ItemHeight, ItemWidth, ItemHeight);
anchor.Arrange(arrangeRect);
Debug.WriteLine(" Arrange:" + anchorIndex + " :" + arrangeRect);
}
return(finalSize);
}
protected override Size MeasureOverride(VirtualizingLayoutContext context, Size availableSize)
{
var realizationRect = context.RealizationRect;
int itemCount = context.ItemCount;
int firstRealizedIndex = FirstRealizedIndexInRect(realizationRect, itemCount);
int lastRealizedIndex = LastRealizedIndexInRect(realizationRect, itemCount);
Debug.WriteLine("Measure:" + realizationRect.ToString());
// Viewport + Buffer Rect.
for (int currentIndex = firstRealizedIndex; currentIndex <= lastRealizedIndex; currentIndex++)
{
var element = context.GetOrCreateElementAt(currentIndex);
element.Measure(new Size(ItemWidth, ItemHeight));
}
// Anchor
var anchorIndex = context.RecommendedAnchorIndex;
if (anchorIndex >= 0)
{
var anchorElement = context.GetOrCreateElementAt(anchorIndex);
anchorElement.Measure(new Size(ItemWidth, ItemHeight));
}
return(new Size(ItemWidth, context.ItemCount * ItemHeight));
}
protected override Size MeasureOverride(VirtualizingLayoutContext context, Size availableSize)
{
var anchorIndex = context.RecommendedAnchorIndex;
SuggestedAnchor = anchorIndex < 0 ? null : context.GetOrCreateElementAt(anchorIndex);
return(base.MeasureOverride(context, availableSize));
}
protected override Size ArrangeOverride(VirtualizingLayoutContext context, Size finalSize)
{
DebugTrace("ArrangeOverride: Viewport" + context.RealizationRect);
for (int realizationIndex = 0; realizationIndex < m_realizedElementBounds.Count; realizationIndex++)
{
int currentDataIndex = m_firstRealizedDataIndex + realizationIndex;
DebugTrace("Arranging " + currentDataIndex);
// Arrange the child. If any alignment needs to be done, it
// can be done here.
var child = context.GetOrCreateElementAt(currentDataIndex);
var arrangeBounds = m_realizedElementBounds[realizationIndex];
arrangeBounds.X -= m_lastExtent.X;
arrangeBounds.Y -= m_lastExtent.Y;
child.Arrange(arrangeBounds);
}
return(finalSize);
}
private Size MeasureElement(VirtualizingLayoutContext context, int index, Size availableSize)
{
var child = context.GetOrCreateElementAt(index);
child.Measure(availableSize);
int estimationBufferIndex = index % m_estimationBuffer.Count;
bool alreadyMeasured = m_estimationBuffer[estimationBufferIndex] != 0;
if (!alreadyMeasured)
{
m_numItemsUsedForEstimation++;
}
m_totalHeightForEstimation -= m_estimationBuffer[estimationBufferIndex];
m_totalHeightForEstimation += child.DesiredSize.Height;
m_estimationBuffer[estimationBufferIndex] = child.DesiredSize.Height;
return(child.DesiredSize);
}