/// <summary>
/// Layout the children of the current layout
/// </summary>
/// <param name="x">X delay</param>
/// <param name="y">Y delay</param>
/// <param name="width">Width constraint to layout</param>
/// <param name="height">Height constraint to layout</param>
protected override void LayoutChildren(double x, double y, double width, double height)
{
foreach (var item in VirtualizingItemsControl.GetDisplayedChildren())
{
item.View.Layout(new Rectangle(x, y + rowHeight * item.Index, width, rowHeight));
}
}
internal void SetVirtualizingItemsControl(VirtualizingItemsControl virtualizingItemsControl)
{
if (this.ScrollOwner != null)
{
this.ScrollOwner.SizeChanged -= this.ScrollOwner_SizeChanged;
this.ScrollOwner.Scrolled -= this.ScrollOwner_Scrolled;
}
this.VirtualizingItemsControl = virtualizingItemsControl;
this.InitializeScrollOwner();
}
/// <summary>
/// Method called when a measurement is asked.
/// </summary>
/// <param name="widthConstraint">Width constraint</param>
/// <param name="heightConstraint">Height constraint</param>
/// <returns>Requested size</returns>
protected override SizeRequest OnMeasure(double widthConstraint, double heightConstraint)
{
this.InitializeScrollOwner();
var firstItem = VirtualizingItemsControl?.GenerateAt(0);
if (firstItem == null)
{
return(base.OnMeasure(widthConstraint, heightConstraint));
}
var request = firstItem.Measure(widthConstraint, double.PositiveInfinity, MeasureFlags.IncludeMargins);
var oldRowHeight = rowHeight;
this.rowHeight = request.Request.Height;
var height = this.VirtualizingItemsControl.ItemsSource.Count * request.Request.Height;
if (oldRowHeight != rowHeight)
{
GenerateItemsForViewport();
}
return(new SizeRequest(new Size(request.Request.Width, height)));
}
