Open up VirtualizingPanel and OrientedVirtualizingPanel
Currently, it is nearly impossible to create a custom virtualizing panel. In WPF we could inherit the base classes to re-use the existing base functionality. But in UWP it is impossible because the base classes have private constructors, and the other classes are sealed. A lot of custom controls do not use virtualization, because it is so hard to implement in UWP. This makes the controls hard or even impossible to use with large collections.
Please open up the base classes for inheritance, and provide a sample how to create a custom virtualizing panel.
Alternatively, provide source code of e.g. ItemsWrapGrid or provide a reference implementation of a custom virtualizing UWP panel that works with ListView and GridView.