[Mir-on-Wayland] add support for "windowed mode"

[AlanGriffiths]

[wmww]

Something will want to consider is having a different mechanism for setting the Wayland display MIr creates than the WAYLAND_DISPLAY environment variable. Ideally Mir would run on the current WAYLAND_DISPLAY, so the user doesn't have to specify the display to run on in a way different from any other application.

I propose adding a --wayland-display, --display-name, --new-display, --serve-display or similar option. If this is specified it (instead of WAYLAND_DISPLAY) will be the display Mir tries to create and serve clients on and WAYLAND_DISPLAY if specified will be used as the host environment instead of X11.

[AlanGriffiths]

Something will want to consider is having a different mechanism for setting the Wayland display MIr creates than the WAYLAND_DISPLAY environment variable. Ideally Mir would run on the current WAYLAND_DISPLAY, so the user doesn't have to specify the display to run on in a way different from any other application.

Ideally people would raise separate issues as separate threads. But this one is a bad idea and needn't be raised. The use of WAYLAND_DISPLAY is the same as with any Wayland compositor: set by the login session for use by both compositor and applications. That's how it should work for normal deployments. (Although we as devs do it a lot running hosted by another DE is not the configuration to be optimised, and is easily scripted: miral-app.)