The Fremantle compositor (aka hildon-desktop) reads the window contents every time those change; converts them to a GLES texture, uploading it to the SGX; and then uses Clutter (GLESv2) to render them to the screen.
An animation actor is just a special type of window that is rendered in a special way. You can configure the compositor (via xatoms) to render any of those windows rotated, scaled, etc. at your pleasure.

If you were to do this with GLES API by yourself (and assuming a composited/non fullscreen mode), the compositor would get your large GLES scaled image and REupload it to the SGX to again convert it a to a texture, thus slowing down the process.

Another example (for SDL_haa) is: http://git.maemo.org/git/sdlhildon/?...a/test/basic.c