internal void EnsureElementSize(
Size availableSize,
VirtualizingLayoutContext context,
double layoutItemWidth,
double LayoutItemHeight,
UniformGridLayoutItemsStretch stretch,
Orientation orientation,
double minRowSpacing,
double minColumnSpacing,
uint maxItemsPerLine)
{
if (maxItemsPerLine == 0)
{
maxItemsPerLine = 1;
}
if (context.ItemCount > 0)
{
// If the first element is realized we don't need to cache it or to get it from the context
var realizedElement = FlowAlgorithm.GetElementIfRealized(0);
if (realizedElement != null)
{
realizedElement.Measure(availableSize);
SetSize(realizedElement, layoutItemWidth, LayoutItemHeight, availableSize, stretch, orientation, minRowSpacing, minColumnSpacing, maxItemsPerLine);
m_cachedFirstElement = null;
}
else
{
if (m_cachedFirstElement == null)
{
// we only cache if we aren't realizing it
m_cachedFirstElement = context.GetOrCreateElementAt(0, ElementRealizationOptions.ForceCreate | ElementRealizationOptions.SuppressAutoRecycle); // expensive
}
m_cachedFirstElement.Measure(availableSize);
SetSize(m_cachedFirstElement, layoutItemWidth, LayoutItemHeight, availableSize, stretch, orientation, minRowSpacing, minColumnSpacing, maxItemsPerLine);
// See if we can move ownership to the flow algorithm. If we can, we do not need a local cache.
bool added = FlowAlgorithm.TryAddElement0(m_cachedFirstElement);
if (added)
{
m_cachedFirstElement = null;
}
}
}
}
private 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);
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);
}
}
internal void EnsureElementSize(
Size availableSize,
VirtualizingLayoutContext context,
double layoutItemWidth,
double LayoutItemHeight,
UniformGridLayoutItemsStretch stretch,
Orientation orientation,
double minRowSpacing,
double minColumnSpacing,
uint maxItemsPerLine)
{
if (maxItemsPerLine == 0)
{
maxItemsPerLine = 1;
}
if (context.ItemCount > 0)
{
// If the first element is realized we don't need to get it from the context
var realizedElement = FlowAlgorithm.GetElementIfRealized(0);
if (realizedElement != null)
{
realizedElement.Measure(availableSize);
SetSize(realizedElement.DesiredSize, layoutItemWidth, LayoutItemHeight, availableSize, stretch, orientation, minRowSpacing, minColumnSpacing, maxItemsPerLine);
}
else
{
// Not realized by flowlayout, so do this now!
if (context.GetOrCreateElementAt(0, ElementRealizationOptions.ForceCreate) is { } firstElement)
{
firstElement.Measure(availableSize);
SetSize(firstElement.DesiredSize, layoutItemWidth, LayoutItemHeight, availableSize, stretch, orientation, minRowSpacing, minColumnSpacing, maxItemsPerLine);
context.RecycleElement(firstElement);
}
}
}
}
