internal void RemoveFromIndex(int index)
{
if (index >= _items.Count)
{
// Item was added/removed but we haven't realized that far yet
return;
}
int numToRemove = _items.Count - index;
_items.RemoveRange(index, numToRemove);
foreach (var kvp in _columnLayout)
{
StaggeredColumnLayout layout = kvp.Value;
for (int i = 0; i < layout.Count; i++)
{
if (layout[i].Index >= index)
{
numToRemove = layout.Count - i;
layout.RemoveRange(i, numToRemove);
break;
}
}
}
}
internal void RemoveRange(int startIndex, int endIndex)
{
for (int i = startIndex; i <= endIndex; i++)
{
if (i > _items.Count)
{
break;
}
StaggeredItem item = _items[i];
item.Height = 0;
item.Top = 0;
// We must recycle all elements to ensure that it gets the correct context
RecycleElementAt(i);
}
foreach (var kvp in _columnLayout)
{
StaggeredColumnLayout layout = kvp.Value;
for (int i = 0; i < layout.Count; i++)
{
if ((startIndex <= layout[i].Index) && (layout[i].Index <= endIndex))
{
int numToRemove = layout.Count - i;
layout.RemoveRange(i, numToRemove);
break;
}
}
}
}
internal void AddItemToColumn(StaggeredItem item, int columnIndex)
{
if (_columnLayout.TryGetValue(columnIndex, out StaggeredColumnLayout columnLayout) == false)
{
columnLayout = new StaggeredColumnLayout();
_columnLayout[columnIndex] = columnLayout;
}
if (columnLayout.Contains(item) == false)
{
columnLayout.Add(item);
}
}
/// <inheritdoc/>
protected override Size ArrangeOverride(VirtualizingLayoutContext context, Size finalSize)
{
if ((context.RealizationRect.Width == 0) && (context.RealizationRect.Height == 0))
{
return(finalSize);
}
var state = (StaggeredLayoutState)context.LayoutState;
// Cycle through each column and arrange the items that are within the realization bounds
for (int columnIndex = 0; columnIndex < state.NumberOfColumns; columnIndex++)
{
StaggeredColumnLayout layout = state.GetColumnLayout(columnIndex);
for (int i = 0; i < layout.Count; i++)
{
StaggeredItem item = layout[i];
double bottom = item.Top + item.Height;
if (bottom < context.RealizationRect.Top)
{
// element is above the realization bounds
continue;
}
if (item.Top <= context.RealizationRect.Bottom)
{
double itemHorizontalOffset = (state.ColumnWidth * columnIndex) + (ColumnSpacing * columnIndex);
Rect bounds = new Rect(itemHorizontalOffset, item.Top, state.ColumnWidth, item.Height);
UIElement element = context.GetOrCreateElementAt(item.Index);
element.Arrange(bounds);
}
else
{
break;
}
}
}
return(finalSize);
}