[Crinus]

I do not like compositing though, at least not the way it is implemented in pretty much every current desktop environment (including Windows) where the composition is synced to the monitor refresh rate, meaning that it will always be at least ~8ms late on average and that is assuming everything else is synchronized - but this is not the case as applications draw their output offscreen to a surface that is picked up by the compositor (the mechanism of which is irrelevant, the application might just render to a compositor provided resource or the compositor might copy a VRAM surface or it may transfer bytes from the system RAM, it doesn't matter much in what i'm describing) which happens asynchronously and then notify the compositor that the window contents have changed which is again picked by compositor asynchronously. This introduces several frames of delay between the application drawing something and it appearing on your monitor. It is not a big problem when you are passively watching something, like a movie or an animation, but when that "something" that is drawn is an immediate reaction to an action you just did (like resizing a window with your mouse) you can "feel" that delay.

With non-composited window systems (which nowadays is pretty much only Win7 with DWM disabled and pure X11/Xorg) all that overhead goes away since applications draw directly to the video memory that is to be presented to the monitor (the GPU might do some minor composition itself but that is irrelevant as there aren't any delays involved).

Compositing would work if all composition was done on the GPU using dedicated hardware (similar to how the GPU already performs composition for the mouse cursor and an overlay that is often used for HUD-like controls like volume control, but those are not general purpose features that can be used for desktop composition) and applications could draw directly to the video surfaces that would be composited pretty much the same way a non-composited desktop can draw directly to the video memory (this would introduce artifacts like tearing but this is something that could be handled separately and to some - like me - tearing is perfectly acceptable for pretty much all interactive actions).

I am not aware of any GPU or window system that does compositing like this though.