private void MeasureTrailing()
{
var constraint = OrientedConstraint.Size;
var index = LastVisibleIndex + 1;
var realizedIndex = index;
while (index < SourceCount && TrailingCacheCount <= Layout.Panel.LeadingTrailingLimit)
{
var element = Realize(index);
if (element == null)
{
index++;
continue;
}
realizedIndex = index;
AddItem(element);
Layout.MeasureChild(element, constraint);
OrientedTrailingSize = OrientedTrailingSize.StackSize(element.DesiredSize);
index++;
TrailingCacheCount++;
}
LastIndex = realizedIndex;
}
private void MeasureFocusedItem(int focusedIndex)
{
if (focusedIndex < 0 || focusedIndex >= SourceCount)
{
return;
}
if (focusedIndex >= FirstIndex && focusedIndex <= LastIndex)
{
return;
}
var focusedItem = Realize(focusedIndex);
if (focusedItem == null)
{
return;
}
if (focusedIndex < FirstIndex)
{
InsertItem(0, focusedItem);
Layout.MeasureChild(focusedItem, OrientedConstraint.Size);
OrientedLeadingSize = OrientedLeadingSize.StackSize(focusedItem.DesiredSize);
}
else
{
AddItem(focusedItem);
Layout.MeasureChild(focusedItem, OrientedConstraint.Size);
OrientedTrailingSize = OrientedTrailingSize.StackSize(focusedItem.DesiredSize);
}
}