If you head on over to the Nokia Labs Qt Blog
there is a post about "multi-process Lighthouse", which is worth reading. It's written by Jørgen Lind about how up until now Qt has lacked a multi-process client/server solution, but now they are looking for the Wayland Display Server to fill this void. Jørgen and other Qt developers ended up writing "Qt Compositor", which is a Nokia Labs project for making Qt-based Wayland compositors.
Qt Compositor's goal is to be "a tool box which is being used as a base layer for other people when they are going to write their own custom Wayland compositors."
Additionally, "Qt-Compositor abstracts away all communication needed by a Wayland compositor. Hence the primary task for someone who implements a custom compositor is how the surfaces will be drawn. On the client side, the display information is sent over the protocol, and is available to all clients through the usual Qt-APIs."
Sounds interesting for the promising Wayland Display Server