How to properly list number of monitors

[Jean Hertel]

Hi Wayland developers,

My name is Jean Hertel and I'm the developer of adriconf[1], a small GUI utility to configure options of mesa drivers.
I'm looking into improving our wayland support and would like to ask a few questions.

Under X11 I can count the number of screens with ScreenCount() macro. After knowing the number of screens I can then query mesa for the name of the driver and options of each of those screens with glXGetScreenDriver(screenNumber) and glXGetDriverConfig (driverName).

Under Wayland/EGL I can use the functions eglGetDisplayDriverName(display) and eglGetDisplayDriverConfig(display) [2].
Wayland provides us with the nice wl_display_connect() function. But for this function I need to known all the display names, the default being "wayland-0".
How can I get the name and/or the number of the displays?

Also, looking into the docs, It's not clear to me if we can have a different GPU backing each screen, can somebody please clarify to me?

Finally, can we have a single display object backing all screens?
Who defines this? The compositor implementation?
My impression from reading the mesa source code is that the display server defines the screens and mesa just accepts it.

Kind regards,
Jean Hertel

[1]: https://github.com/jlHertel/adriconf/
[2]: https://www.khronos.org/registry/EGL/extensions/MESA/EGL_MESA_query_driver.txt