Avalon Dissected
What is Avalon?
Simply put, Avalon is a set of CLR APIs for graphics and multimedia on the next-generation Windows (Longhorn) platform. If history serves, Avalon is how client programming will get done for at least a decade from the point Longhorn is released.
Kiss GDI Goodbye
GDI has been the core API for graphics since the beginning of time in Windows and there have been few advancements over the years, most recently GDI+. While GDI+ will still be supported in Longhorn for backward compatibility, one thing should be made completely clear: Avalon is it's replacement. Avalon is not a layer on top of GDI+. In fact, Avalon has an intimate relationship with a much richer set of APIs under its covers: DirectX. Therefore, you should think of the GDI+ and Avalon as side-by-side technologies on Longhorn. Using one essentially means you won't/shouldn't be using the other. I say “essentially” because it is possible to host an Avalon visual in the GDI+ world and vice versa, but according to the documentation on the subject there will be a limited amount of interop possible and from what I recall from a PDC session I attended, you should not expect great performance. I guess we should think of this approach as we think of COM interop in .NET. Without knowing all of the limitations though, that might even be a little optimistic.
The Layers of Avalon
Avalon is actually composed of several layers, each of which I will discuss in individual articles in some detail. Hopefully I can provide a little more information than you would get out of simply reading the SDK as well as a little personal insight/experience.
Part 1: Core Technologies
Part 2: UIElement <- FrameworkElement <- Control
Part 3: Vector Graphics (coming soon)
... more to come ...