public Size MeasureElement(
ILayoutable element,
int index,
Size availableSize,
VirtualizingLayoutContext context)
{
var measureSize = _algorithmCallbacks.Algorithm_GetMeasureSize(index, availableSize, context);
element.Measure(measureSize);
var provisionalArrangeSize = _algorithmCallbacks.Algorithm_GetProvisionalArrangeSize(index, measureSize, element.DesiredSize, context);
_algorithmCallbacks.Algorithm_OnElementMeasured(element, index, availableSize, measureSize, element.DesiredSize, provisionalArrangeSize, context);
return provisionalArrangeSize;
}
void MakeAnchor(
VirtualizingLayoutContext context,
int index,
Size availableSize)
{
m_elementManager.ClearRealizedRange();
// FlowLayout requires that the anchor is the first element in the row.
var internalAnchor = m_algorithmCallbacks.Algorithm_GetAnchorForTargetElement(index, availableSize, context);
global::System.Diagnostics.Debug.Assert(internalAnchor.Index <= index);
// No need to set the position of the anchor.
// (0,0) is fine for now since the extent can
// grow in any direction.
for (int dataIndex = internalAnchor.Index; dataIndex < index + 1; ++dataIndex)
{
var element = context.GetOrCreateElementAt(dataIndex, ElementRealizationOptions.ForceCreate | ElementRealizationOptions.SuppressAutoRecycle);
element.Measure(m_algorithmCallbacks.Algorithm_GetMeasureSize(dataIndex, availableSize, context));
m_elementManager.Add(element, dataIndex);
}
}