Earlier quoted context omitted.
Yes, but why is the compositor dealing with this? Shouldn't the compositor simply be deciding which windows go where (X, Y, and Z positions) and leave the rendering to another API? Why does every different take on a window manager need to re-do all this work?
Turning the question around, what other part of the system _could_ do this job? And how would the compositor do any part of its job if it doesn't have access to both window contents and displays? I'm not super deep in this area but a straight-forward example of a non-managed app and a color-aware graphics app running on a laptop with an external display seems like it is enough to figure out how things need to go toge…
It's like going to Taco Bell and they make you grind your own corn for your tortillas.