Blurs, Window Animations and Shadows

KDE has API where applications can request special animations/looks for windows from the window manager. This includes amongst other things

• blurring the background of window if it is transparent
• changing contrast, luminosity or saturation of things behind transparent regions so things on top aer still readable
• when showing/hiding the window, slide it in/out from/to the screen border
• provide a different set of shadows that should be used while continuing to use window manager provided titlebar

On X11 we used special Atoms on the window for that. On Wayland we have custom protocols that the backend of this library can use.
To identify the window in this protocol we need to use the wl_surface.

I am not sure how this compares to the brainstormed features on other platforms.