XScreenSaver, Wayland and locking.

Welp, I got crickets in answer to my question, "How do I find the wl_surface backing an Xwayland X11 Window?" and that does not bode well for XScreenSaver ever being able to lock your screen on Wayland. The only...
https://jwz.org/b/ykrj

Welp. All that lovely "AI" derailment aside, we now have an answer:

It is literally impossible for XScreenSaver to lock the screen under Wayland. Cannot be done. None of the extant, spottily-supported "protocols" will allow the screen to be locked while an Xwayland surface is visible.

Great job, everybody. Perfect, no notes.

@jwz

That is a pretty tricky thing to support, I'd imagine, given the differences between Wayland and X11. Is there a specific reason you want to use a locker via XWayland instead of the various Wayland native screen lockers that exist?

@boo_ Show me how to make any of the extant native screen lockers run an arbitrary graphics-drawing program of my choice while the screen is locked.

Go ahead, I'll wait.

@jwz @boo_ I do not think it meets your criteria for xscreensaver, but maybe swaylock-plugin (a fork of swaylock) would be helpful in your research? ​

Edit: Sorry for spam. I was too slow and missed the latest reply.