protected override Size MeasureOverride(Size availableSize)
{
if (m_isLayoutInProgress)
{
throw new Exception("Reentrancy detected during layout.");
}
if (IsProcessingCollectionChange)
{
throw new Exception("Cannot run layout in the middle of a collection change.");
}
m_viewportManager.OnOwnerMeasuring();
m_isLayoutInProgress = true;
try
{
ViewManager.PrunePinnedElements();
Rect extent = default;
Size desiredSize = default;
if (Layout is Layout layout)
{
var layoutContext = GetLayoutContext();
// Checking if we have an data template and it is empty
if (m_isItemTemplateEmpty)
{
// Has no content, so we will draw nothing and request zero space
extent = new Rect(m_layoutOrigin.X, m_layoutOrigin.Y, 0, 0);
}
else
{
desiredSize = layout.Measure(layoutContext, availableSize);
extent = new Rect(m_layoutOrigin.X, m_layoutOrigin.Y, desiredSize.Width, desiredSize.Height);
}
// Clear auto recycle candidate elements that have not been kept alive by layout - i.e layout did not
// call GetElementAt(index).
var children = Children;
for (int i = 0; i < children.Count; ++i)
{
var element = children[i];
var virtInfo = GetVirtualizationInfo(element);
if (virtInfo.Owner == ElementOwner.Layout &&
virtInfo.AutoRecycleCandidate &&
!virtInfo.KeepAlive)
{
ClearElementImpl(element);
}
}
}
m_viewportManager.SetLayoutExtent(extent);
m_lastAvailableSize = availableSize;
m_lastChildDesiredSizeChangedCounter = m_childDesiredSizeChangedCounter = 0;
return(desiredSize);
}
finally
{
m_isLayoutInProgress = false;
}
}
protected override Size ArrangeOverride(Size finalSize)
{
if (m_isLayoutInProgress)
{
throw new Exception("Reentrancy detected during layout.");
}
if (IsProcessingCollectionChange)
{
throw new Exception("Cannot run layout in the middle of a collection change.");
}
m_isLayoutInProgress = true;
try
{
Size arrangeSize = default;
if (Layout is Layout layout)
{
arrangeSize = layout.Arrange(GetLayoutContext(), finalSize);
}
// The view manager might clear elements during this call.
// That's why we call it before arranging cleared elements
// off screen.
ViewManager.OnOwnerArranged();
var children = Children;
for (int i = 0; i < children.Count; ++i)
{
var element = children[i];
var virtInfo = GetVirtualizationInfo(element);
virtInfo.KeepAlive = false;
if (virtInfo.Owner == ElementOwner.ElementFactory ||
virtInfo.Owner == ElementOwner.PinnedPool)
{
// Toss it away. And arrange it with size 0 so that XYFocus won't use it.
element.Arrange(new Rect(
ClearedElementsArrangePosition.X - element.DesiredSize.Width,
ClearedElementsArrangePosition.Y - element.DesiredSize.Height,
0.0,
0.0));
}
else
{
var newBounds = CachedVisualTreeHelpers.GetLayoutSlot(element as FrameworkElement);
if (virtInfo.ArrangeBounds != InvalidRect &&
newBounds != virtInfo.ArrangeBounds)
{
AnimationManager.OnElementBoundsChanged(element, virtInfo.ArrangeBounds, newBounds);
}
virtInfo.ArrangeBounds = newBounds;
}
}
m_viewportManager.OnOwnerArranged();
AnimationManager.OnOwnerArranged();
return(arrangeSize);
}
finally
{
m_isLayoutInProgress = false;
}
}
