Wayland and X11 emits signal window-added in different states
I'm writing a gnome-shell extension for placing new windows on a workspace in the "true" top-left position of the workspace. Code available here: https://github.com/christensson/gnome-better-window-placement
The extension listens to the window-added signal (emitted per workspace) and when received it places the window if that window is the first window on the workspace. (Only the first window per workspace needs to be explicitly placed since mutter tries to place new windows next to any already existing windows.)
However this doesn't work that good. On X11 it works good, on Wayland it doesn't. On Wayland it works something like every ten time.
The timing of when the window-added signal is sent seems to be different in X11 and Wayland.
Also see the discussion in !11 (closed)