public void UpdatePin(IControl element, bool addPin)
{
var parent = element.VisualParent;
var child = (IVisual)element;
while (parent != null)
{
if (parent is ItemsRepeater repeater)
{
var virtInfo = ItemsRepeater.GetVirtualizationInfo((IControl)child);
if (virtInfo.IsRealized)
{
if (addPin)
{
virtInfo.AddPin();
}
else if (virtInfo.IsPinned)
{
if (virtInfo.RemovePin() == 0)
{
// ElementFactory is invoked during the measure pass.
// We will clear the element then.
repeater.InvalidateMeasure();
}
}
}
}
child = parent;
parent = child.VisualParent;
}
}
public void ClearElementToElementFactory(IControl element)
{
_owner.OnElementClearing(element);
if (_owner.ItemTemplateShim != null)
{
_owner.ItemTemplateShim.RecycleElement(_owner, element);
}
else
{
// No ItemTemplate to recycle to, remove the element from the children collection.
if (!_owner.Children.Remove(element))
{
throw new InvalidOperationException("ItemsRepeater's child not found in its Children collection.");
}
}
var virtInfo = ItemsRepeater.GetVirtualizationInfo(element);
virtInfo.MoveOwnershipToElementFactory();
if (_lastFocusedElement == element)
{
// Focused element is going away. Remove the tracked last focused element
// and pick a reasonable next focus if we can find one within the layout
// realized elements.
MoveFocusFromClearedIndex(virtInfo.Index);
}
}
private void UpdateFocusedElement()
{
IControl?focusedElement = null;
var child = FocusManager.Instance?.Current;
if (child != null)
{
var parent = child.VisualParent;
var owner = _owner;
// Find out if the focused element belongs to one of our direct
// children.
while (parent != null)
{
if (parent is ItemsRepeater repeater)
{
var element = child as IControl;
if (repeater == owner &&
element is not null &&
ItemsRepeater.GetVirtualizationInfo(element).IsRealized)
{
focusedElement = element;
}
break;
}
child = parent as IInputElement;
parent = child?.VisualParent;
}
}
// If the focused element has changed,
// we need to unpin the old one and pin the new one.
if (_lastFocusedElement != focusedElement)
{
if (_lastFocusedElement != null)
{
UpdatePin(_lastFocusedElement, false /* addPin */);
}
if (focusedElement != null)
{
UpdatePin(focusedElement, true /* addPin */);
}
_lastFocusedElement = focusedElement;
}
}
public void ClearElementToElementFactory(IControl element)
{
var virtInfo = ItemsRepeater.GetVirtualizationInfo(element);
var clearedIndex = virtInfo.Index;
_owner.OnElementClearing(element);
_owner.ItemTemplateShim.RecycleElement(_owner, element);
virtInfo.MoveOwnershipToElementFactory();
if (_lastFocusedElement == element)
{
// Focused element is going away. Remove the tracked last focused element
// and pick a reasonable next focus if we can find one within the layout
// realized elements.
MoveFocusFromClearedIndex(clearedIndex);
}
}
private IControl GetElementFromUniqueIdResetPool(int index)
{
IControl element = null;
// See if you can get it from the reset pool.
if (_isDataSourceStableResetPending)
{
element = _resetPool.Remove(index);
if (element != null)
{
// Make sure that the index is updated to the current one
var virtInfo = ItemsRepeater.GetVirtualizationInfo(element);
virtInfo.MoveOwnershipToLayoutFromUniqueIdResetPool();
UpdateElementIndex(element, virtInfo, index);
}
}
return(element);
}
// We need to clear the datacontext to prevent crashes from happening,
// however we only do that if we were the ones setting it.
// That is when one of the following is the case (numbering taken from line ~642):
// 1.2 No ItemTemplate, data is not a UIElement
// 2.1 ItemTemplate, data is not FrameworkElement
// 2.2.2 Itemtemplate, data is FrameworkElement, ElementFactory returned Element different to data
//
// In all of those three cases, we the ItemTemplateShim is NOT null.
// Luckily when we create the items, we store whether we were the once setting the DataContext.
public void ClearElementToElementFactory(IControl element)
{
_owner.OnElementClearing(element);
var virtInfo = ItemsRepeater.GetVirtualizationInfo(element);
virtInfo.MoveOwnershipToElementFactory();
// During creation of this object, we were the one setting the DataContext, so clear it now.
if (virtInfo.MustClearDataContext)
{
element.DataContext = null;
}
if (_owner.ItemTemplateShim != null)
{
var context = _elementFactoryRecycleArgs ??= new ElementFactoryRecycleArgs();
context.Element = element;
context.Parent = _owner;
_owner.ItemTemplateShim.RecycleElement(context);
context.Element = null;
context.Parent = null;
}
else
{
// No ItemTemplate to recycle to, remove the element from the children collection.
if (!_owner.Children.Remove(element))
{
throw new InvalidOperationException("ItemsRepeater's child not found in its Children collection.");
}
}
if (_lastFocusedElement == element)
{
// Focused element is going away. Remove the tracked last focused element
// and pick a reasonable next focus if we can find one within the layout
// realized elements.
MoveFocusFromClearedIndex(virtInfo.Index);
}
}
public void ClearElement(IControl element, bool isClearedDueToCollectionChange)
{
var virtInfo = ItemsRepeater.GetVirtualizationInfo(element);
var index = virtInfo.Index;
bool cleared =
ClearElementToUniqueIdResetPool(element, virtInfo) ||
ClearElementToPinnedPool(element, virtInfo, isClearedDueToCollectionChange);
if (!cleared)
{
ClearElementToElementFactory(element);
}
// Both First and Last indices need to be valid or default.
if (index == _firstRealizedElementIndexHeldByLayout && index == _lastRealizedElementIndexHeldByLayout)
{
// First and last were pointing to the same element and that is going away.
InvalidateRealizedIndicesHeldByLayout();
}
else if (index == _firstRealizedElementIndexHeldByLayout)
{
// The FirstElement is going away, shrink the range by one.
++_firstRealizedElementIndexHeldByLayout;
}
else if (index == _lastRealizedElementIndexHeldByLayout)
{
// Last element is going away, shrink the range by one at the end.
--_lastRealizedElementIndexHeldByLayout;
}
else
{
// Index is either outside the range we are keeping track of or inside the range.
// In both these cases, we just keep the range we have. If this clear was due to
// a collection change, then in the CollectionChanged event, we will invalidate these guys.
}
}
public PinnedElementInfo(IControl element)
{
PinnedElement = element;
VirtualizationInfo = ItemsRepeater.GetVirtualizationInfo(element);
}
public void OnItemsSourceChanged(object sender, NotifyCollectionChangedEventArgs args)
{
// Note: For items that have been removed, the index will not be touched. It will hold
// the old index before it was removed. It is not valid anymore.
switch (args.Action)
{
case NotifyCollectionChangedAction.Add:
{
var newIndex = args.NewStartingIndex;
var newCount = args.NewItems.Count;
EnsureFirstLastRealizedIndices();
if (newIndex <= _lastRealizedElementIndexHeldByLayout)
{
_lastRealizedElementIndexHeldByLayout += newCount;
foreach (var element in _owner.Children)
{
var virtInfo = ItemsRepeater.GetVirtualizationInfo(element);
var dataIndex = virtInfo.Index;
if (virtInfo.IsRealized && dataIndex >= newIndex)
{
UpdateElementIndex(element, virtInfo, dataIndex + newCount);
}
}
}
else
{
// Indices held by layout are not affected
// We could still have items in the pinned elements that need updates. This is usually a very small vector.
for (var i = 0; i < _pinnedPool.Count; ++i)
{
var elementInfo = _pinnedPool[i];
var virtInfo = elementInfo.VirtualizationInfo;
var dataIndex = virtInfo.Index;
if (virtInfo.IsRealized && dataIndex >= newIndex)
{
var element = elementInfo.PinnedElement;
UpdateElementIndex(element, virtInfo, dataIndex + newCount);
}
}
}
break;
}
case NotifyCollectionChangedAction.Replace:
{
// Requirement: oldStartIndex == newStartIndex. It is not a replace if this is not true.
// Two cases here
// case 1: oldCount == newCount
// indices are not affected. nothing to do here.
// case 2: oldCount != newCount
// Replaced with less or more items. This is like an insert or remove
// depending on the counts.
var oldStartIndex = args.OldStartingIndex;
var newStartingIndex = args.NewStartingIndex;
var oldCount = args.OldItems.Count;
var newCount = args.NewItems.Count;
if (oldStartIndex != newStartingIndex)
{
throw new NotSupportedException("Replace is only allowed with OldStartingIndex equals to NewStartingIndex.");
}
if (oldCount == 0)
{
throw new NotSupportedException("Replace notification with args.OldItemsCount value of 0 is not allowed. Use Insert action instead.");
}
if (newCount == 0)
{
throw new NotSupportedException("Replace notification with args.NewItemCount value of 0 is not allowed. Use Remove action instead.");
}
int countChange = newCount - oldCount;
if (countChange != 0)
{
// countChange > 0 : countChange items were added
// countChange < 0 : -countChange items were removed
foreach (var element in _owner.Children)
{
var virtInfo = ItemsRepeater.GetVirtualizationInfo(element);
var dataIndex = virtInfo.Index;
if (virtInfo.IsRealized)
{
if (dataIndex >= oldStartIndex + oldCount)
{
UpdateElementIndex(element, virtInfo, dataIndex + countChange);
}
}
}
EnsureFirstLastRealizedIndices();
_lastRealizedElementIndexHeldByLayout += countChange;
}
break;
}
case NotifyCollectionChangedAction.Remove:
{
var oldStartIndex = args.OldStartingIndex;
var oldCount = args.OldItems.Count;
foreach (var element in _owner.Children)
{
var virtInfo = ItemsRepeater.GetVirtualizationInfo(element);
var dataIndex = virtInfo.Index;
if (virtInfo.IsRealized)
{
if (virtInfo.AutoRecycleCandidate && oldStartIndex <= dataIndex && dataIndex < oldStartIndex + oldCount)
{
// If we are doing the mapping, remove the element who's data was removed.
_owner.ClearElementImpl(element);
}
else if (dataIndex >= (oldStartIndex + oldCount))
{
UpdateElementIndex(element, virtInfo, dataIndex - oldCount);
}
}
}
InvalidateRealizedIndicesHeldByLayout();
break;
}
case NotifyCollectionChangedAction.Reset:
if (_owner.ItemsSourceView.HasKeyIndexMapping)
{
_isDataSourceStableResetPending = true;
}
// Walk through all the elements and make sure they are cleared, they will go into
// the stable id reset pool.
foreach (var element in _owner.Children)
{
var virtInfo = ItemsRepeater.GetVirtualizationInfo(element);
if (virtInfo.IsRealized && virtInfo.AutoRecycleCandidate)
{
_owner.ClearElementImpl(element);
}
}
InvalidateRealizedIndicesHeldByLayout();
break;
}
}
