Any sort app-level API akin to Core Animation / DirectComposition?

(by “app-level” I mean to be used within my own apps, vs. something built into the windowing system as a whole - unless of course it exposes an API that I can work with purely within the boundaries of my own app)

For a few years I’ve been slowly building up libraries for cross-platform API development. On Linux I’m building on top of GTK/Cairo for windowing/drawing, but looking ahead I’m wondering if I’m going to be able to have feature parity with Windows and Mac when it comes to smoothly-animated layers.

What are people using for this currently? Suppose I want to draw some content into a bitmap/layer and have it smoothly animate (fade out, scale up, move across the window), what would I reach for?