private void HandleItemRemoved(int index, object item)
{
// check if the item is in the view
if (_filter != null && !_filter(item))
{
return;
}
// compute index into view
if (index < 0 || index >= _view.Count || !Equals(_view[index], item))
{
index = _view.IndexOf(item);
}
if (index < 0)
{
return;
}
// remove item from view
_view.RemoveAt(index);
// keep selection on the same item
if (index <= CurrentPosition)
{
CurrentPosition--;
}
// notify listeners
var e = new VectorChangedEventArgs(CollectionChange.ItemRemoved, index);
OnVectorChanged(e);
}
private void HandleItemAdded(int index, object item)
{
// if the new item is filtered out of view, no work
if (_filter != null && !_filter(item))
{
return;
}
// compute insert index
if (_sort.Count > 0)
{
// sorted: insert at sort position
_sortProps.Clear();
index = _view.BinarySearch(item, this);
if (index < 0)
{
index = ~index;
}
}
else if (_filter != null)
{
// if the source is not a list (e.g. enum), then do a full refresh
if (_sourceList == null)
{
HandleSourceChanged();
return;
}
// find insert index
// count invisible items below the insertion point and
// subtract from the number of items in the view
// (counting from the bottom is more efficient for the
// most common case which is appending to the source collection)
var visibleBelowIndex = 0;
for (int i = index; i < _sourceList.Count; i++)
{
if (!_filter(_sourceList[i]))
{
visibleBelowIndex++;
}
}
index = _view.Count - visibleBelowIndex;
}
// add item to view
_view.Insert(index, item);
// keep selection on the same item
if (index <= CurrentPosition)
{
CurrentPosition++;
}
// notify listeners
var e = new VectorChangedEventArgs(CollectionChange.ItemInserted, index);
OnVectorChanged(e);
}