Comment 2 for bug 1646449

I don't think it "comes for free" with making nested a loadable "platform" module. There are abstractions missing in the logic.

Currently the nested code simply assumes that the intent is a fullscreen display on every output. C.f. mgn::Display::create_surfaces().

We need to disentangle the code somewhat so that the configuration can override that default

E.g. the code calling mir_surface_spec_set_fullscreen_on_output() is mgn::MirClientHostConnection::create_surface(), and that doesn't have the context to know whether fullscreen is wanted.