This would help out clients that wait a bit longer until they create and attach a buffer to the surface. This is about panel surfaces which are required to have a valid geometry such that the compositor knows the remaining geometry which can be sent to regular applications when sending the configure event. The issue is trigger by the fact that the client shell sends ready() before actually creating any buffer and attach to the surface.

Both Qt and GTK seem to be do this in time, but for the wayland implementation in chromium does not. For Qt we delay ready() request for the toolkit to do that (as that's not under our control) and for GTK I see doing it before sending the ack for the configure events.

The issue is only present on the chromium side of things where the client does ack for the configure events then we send ready() event. One option would be notified in WAM whenever that happens – which I've added SPEC-4000.

This is an alternative approach where we try to fix that in the compositor where we wait until the clients does a commit with a buffer attach for the panel surface and then start presenting.