[GSoC] Support of pluggable theming engines

[Ivan Akulinchev]

> I mean window class manifest data is already parsed in
> ntdll/actctx.c and FindActCtxSectionStringW() already returns
> versioned class names.

Good news. I have less work to do.

> I mean where in user controls such transition effects are supposed
> to be used?

Take a look at the default button in Vista and 7. It changes here and
there between PBS_DEFAULTED and PBS_DEFAULTED_ANIMATING (the last one
not described in MSDN, sorry). If you hover the mouse, the state will
be changed smoothly as well. So the push button is the candidate
number one. But other controls have animations too, perhaps you didn't
recognize it due to a very small transition time.

Speaking about GTK, animated widgets can await you everywhere. For
example, in Adwaita (the default theme from GNOME3) tabs have the same
behavior as buttons in Windows Vista. For this reason all controls
should support animated transitions.