Wayland had sub-surfaces support added to its core protocol
a few months back and it enhances several common desktop use-cases
. We've seen GNOME's Mutter-Wayland component gain initial sub-surfaces support
and now with the recent Wayland 1.4 release
it supports sub-surfaces full-on.
Mutter-Wayland 3.11.5 was released today as the window/compositing window manager running directly on Wayland. This update for the GNOME 3.11.5 development release has support for the Wayland sub-surfaces protocol. This update also has a handful of bug-fixes -- including some shared with Mutter 3.11.5 itself -- like fixing client-side decoration title-bars being placed off-screen and fixing the configuration of cloned monitors.
More details on Mutter-Wayland 3.11.5 can be discovered from its release announcement