That little layer on top is the one beneath their app with which they interact, is it not? I'm really asking, not being a Windows developer but looking to get into it - and being a bit confused as to how to proceed.
It goes like this, back when Longhorn was the codename for Windows Vista, with the big plans of using .NET for everything, the next generation UI engine was named Avalon.
Parts of it eventually became what is known as WPF. The whole set of concepts that it embraces are as follows:
- XML based "language" for describing UI layouts (XAML)
- A set of .NET APIs for buttons, dialogs, windows, and so on
- A set of .NET APIs for manipulating the XAML DOM
- A set of .NET APIs for handling application resources
- A set of abstraction concepts, namely binding, data templates, triggers, MVVM, storyboards
When Silverlight came out, the team responsible for it adapted all these concepts to the platform. Similarly to the WinRT platform.
The main differences are the XML namespaces used by XAML, which expose different set of UI widgets in each platform.
Also some .NET APIs are a bit different as the classes aren't 100% equal across all platforms, e.g. TypeConverters are not available in WinRT.
However those basic concepts originally from Avalon are still there.
