[hulitu]

> To put it simply, picom needs to fetch the window tree from X. But there is no way to get the whole tree in one go

There are a lot of WMs who offer a window list (twm, fvwm). Maybe the guy shall take a look how they do it.

And requests to the X server are not syncroneus.

[MadnessASAP]

As they mention, the Window Manager, being the authority on which windows are displayed would obviously have that information. Picoms issue is that it is seperate from the WM and does not have access to that, it needs to go through the X server to discover the windows.