Add a compositor thread to WPF

Today it's incredibly hard to make smooth animations in WPF. And kind of computation done on the UI thread will make the animation jerky.

Both Silverlight and UWP have a compositor thread: a thread dedicated to rendering operations that can work concurrently with the UI thread. It's capable only of simple animations (translation, rotation, transparency...) that do not affect the overall layout (and so do not require a recomputation of the logical tree). I believe this would be a great addition to WPF.