private IControl GetElementFromElementFactory(int index)
{
// The view generator is the provider of last resort.
var itemTemplateFactory = _owner.ItemTemplateShim;
if (itemTemplateFactory == null)
{
// If no ItemTemplate was provided, use a default
var factory = FuncDataTemplate.Default;
_owner.ItemTemplate = factory;
itemTemplateFactory = _owner.ItemTemplateShim;
}
var data = _owner.ItemsSourceView.GetAt(index);
var element = itemTemplateFactory.GetElement(_owner, data);
var virtInfo = ItemsRepeater.TryGetVirtualizationInfo(element);
if (virtInfo == null)
{
virtInfo = ItemsRepeater.CreateAndInitializeVirtualizationInfo(element);
}
// Prepare the element
element.DataContext = data;
virtInfo.MoveOwnershipToLayoutFromElementFactory(
index,
/* uniqueId: */
_owner.ItemsSourceView.HasKeyIndexMapping ?
_owner.ItemsSourceView.KeyFromIndex(index) :
string.Empty);
// The view generator is the only provider that prepares the element.
var repeater = _owner;
// Add the element to the children collection here before raising OnElementPrepared so
// that handlers can walk up the tree in case they want to find their IndexPath in the
// nested case.
var children = repeater.Children;
if (element.VisualParent != repeater)
{
children.Add(element);
}
repeater.OnElementPrepared(element, index);
// Update realized indices
_firstRealizedElementIndexHeldByLayout = Math.Min(_firstRealizedElementIndexHeldByLayout, index);
_lastRealizedElementIndexHeldByLayout = Math.Max(_lastRealizedElementIndexHeldByLayout, index);
return(element);
}
// There are several cases handled here with respect to which element gets returned and when DataContext is modified.
//
// 1. If there is no ItemTemplate:
// 1.1 If data is an IControl -> the data is returned
// 1.2 If data is not an IControl -> a default DataTemplate is used to fetch element and DataContext is set to data
//
// 2. If there is an ItemTemplate:
// 2.1 If data is not an IControl -> Element is fetched from ElementFactory and DataContext is set to the data
// 2.2 If data is an IControl:
// 2.2.1 If Element returned by the ElementFactory is the same as the data -> Element (a.k.a. data) is returned as is
// 2.2.2 If Element returned by the ElementFactory is not the same as the data
// -> Element that is fetched from the ElementFactory is returned and
// DataContext is set to the data's DataContext (if it exists), otherwise it is set to the data itself
private IControl GetElementFromElementFactory(int index)
{
// The view generator is the provider of last resort.
var data = _owner.ItemsSourceView !.GetAt(index);
var providedElementFactory = _owner.ItemTemplateShim;
IElementFactory GetElementFactory()
{
if (providedElementFactory == null)
{
var factory = FuncDataTemplate.Default;
_owner.ItemTemplate = factory;
return(_owner.ItemTemplateShim !);
}
return(providedElementFactory);
}
IControl GetElement()
{
if (providedElementFactory == null)
{
if (data is IControl dataAsElement)
{
return(dataAsElement);
}
}
var elementFactory = GetElementFactory();
var args = _elementFactoryGetArgs ??= new ElementFactoryGetArgs();
try
{
args.Data = data;
args.Parent = _owner;
args.Index = index;
return(elementFactory.GetElement(args));
}
finally
{
args.Data = null;
args.Parent = null;
}
}
var element = GetElement();
var virtInfo = ItemsRepeater.TryGetVirtualizationInfo(element);
if (virtInfo == null)
{
virtInfo = ItemsRepeater.CreateAndInitializeVirtualizationInfo(element);
}
// Clear flag
virtInfo.MustClearDataContext = false;
if (data != element)
{
// Prepare the element
element.DataContext = data;
virtInfo.MustClearDataContext = true;
}
virtInfo.MoveOwnershipToLayoutFromElementFactory(
index,
/* uniqueId: */
_owner.ItemsSourceView.HasKeyIndexMapping ?
_owner.ItemsSourceView.KeyFromIndex(index) :
string.Empty);
// The view generator is the only provider that prepares the element.
var repeater = _owner;
// Add the element to the children collection here before raising OnElementPrepared so
// that handlers can walk up the tree in case they want to find their IndexPath in the
// nested case.
var children = repeater.Children;
if (element.VisualParent != repeater)
{
children.Add(element);
}
repeater.OnElementPrepared(element, virtInfo);
// Update realized indices
_firstRealizedElementIndexHeldByLayout = Math.Min(_firstRealizedElementIndexHeldByLayout, index);
_lastRealizedElementIndexHeldByLayout = Math.Max(_lastRealizedElementIndexHeldByLayout, index);
return(element);
}
