/// <summary>
/// 仮想化を実行します。
/// </summary>
private void Present()
{
_presenting = false;
if (Layouter == null)
{
return;
}
Layouter.Measure(new Size(double.PositiveInfinity, double.PositiveInfinity));
var elements = new HashSet <ControlBase>();
var viewport = Viewport;
_childRectDic.Clear();
Layouter.CalcRectDic(_childRectDic, new Point());
foreach (var item in _childRectDic)
{
if (viewport.IntersectsWith(item.Value))
{
elements.Add(item.Key);
}
}
// MEMO : 表示中のものを表示できる分だけのホストを作ります。
while (_visualChildren.Count < elements.Count)
{
var e = new VirtualElementHost();
AddVisualChild(e);
_visualChildren.Add(e);
_unusedElements.Add(e);
}
foreach (var c in _visualChildren)
{
if (c.Content != null && !elements.Contains(c.Content))
{
_elements.Remove(c.Content);
c.Content = null;
c.Visibility = Visibility.Collapsed;
_unusedElements.Add(c);
}
}
foreach (var item in elements)
{
UIElement element;
if (!_elements.TryGetValue(item, out element))
{
var index = _unusedElements.Count - 1;
var t = _unusedElements[index];
_unusedElements.RemoveAt(index);
t.Content = item;
t.Visibility = Visibility.Visible;
_elements.Add(item, t);
t.InvalidateMeasure();
t.InvalidateVisual();
}
else
{
if (item.MeasureDirty)
{
element.InvalidateMeasure();
}
if (item.ArrangeDirty)
{
element.InvalidateVisual();
}
}
}
InvalidateMeasure();
InvalidateVisual();
}