void MoveExistingItems(int index, int offset)
{
// This is a little horrible. I should really collapse the existing
// RangeCollection so that every > the current index is decremented by 1.
// This is easier for now though. I may think of a better way later on.
RangeCollection newRanges = new RangeCollection();
List <int> list = new List <int> ();
for (int i = 0; i < RealizedElements.Count; i++)
{
list.Add(RealizedElements [i]);
}
if (offset > 0)
{
list.Reverse();
}
foreach (int i in list)
{
int oldIndex = i;
if (oldIndex < index)
{
newRanges.Add(oldIndex);
}
else
{
newRanges.Add(oldIndex + offset);
var container = ContainerIndexMap [oldIndex];
ContainerIndexMap.Remove(container, oldIndex);
ContainerIndexMap.Add(container, oldIndex + offset);
}
}
RealizedElements = newRanges;
}
internal DependencyObject GenerateNext(out bool isNewlyRealized)
{
if (GenerationState == null)
{
throw new InvalidOperationException("Cannot call GenerateNext before calling StartAt");
}
int index;
// This is relative to the realised elements.
int startAt = GenerationState.Position.Index;
if (startAt == -1)
{
if (GenerationState.Position.Offset < 0)
{
index = Owner.Items.Count + GenerationState.Position.Offset;
}
else if (GenerationState.Position.Offset == 0)
{
index = 0;
}
else
{
index = GenerationState.Position.Offset - 1;
}
}
else if (startAt >= 0 && startAt < RealizedElements.Count)
{
// We're starting relative to an already realised element
index = RealizedElements [startAt] + GenerationState.Position.Offset;
}
else
{
index = -1;
}
bool alreadyRealized = RealizedElements.Contains(index);
if (!GenerationState.AllowStartAtRealizedItem && alreadyRealized && GenerationState.Position.Offset == 0)
{
index += GenerationState.Step;
alreadyRealized = RealizedElements.Contains(index);
}
if (index < 0 || index >= Owner.Items.Count)
{
isNewlyRealized = false;
return(null);
}
if (alreadyRealized)
{
GenerationState.Position = new GeneratorPosition(RealizedElements.IndexOf(index), GenerationState.Step);
isNewlyRealized = false;
return(ContainerIndexMap [index]);
}
DependencyObject container;
var item = Owner.Items [index];
if (Owner.IsItemItsOwnContainer(item))
{
container = (DependencyObject)item;
isNewlyRealized = true;
}
else
{
if (Cache.Count == 0)
{
container = Owner.GetContainerForItem();
isNewlyRealized = true;
}
else
{
container = Cache.Dequeue();
isNewlyRealized = false;
}
ContentControl c = container as ContentControl;
if (c != null)
{
c.ContentSetsParent = false;
}
}
FrameworkElement f = container as FrameworkElement;
if (f != null && !(item is UIElement))
{
f.DataContext = item;
}
RealizedElements.Add(index);
ContainerIndexMap.Add(container, index);
ContainerItemMap.Add(container, item);
GenerationState.Position = new GeneratorPosition(RealizedElements.IndexOf(index), GenerationState.Step);
return(container);
}