When my system boots, before I log in, the X-server starts up and chooses a configuration for my displays.
It chooses incorrectly. What controls that configuration and how can I force it to be what I choose, before I log in? I already have a script that runs immediately after I log in, but I would like the monitors and mouse to have correct layout, and hence a sensible behavior during the login process. What file(s) do I need to edit to control this, or where should I put a script?
Edit: The suggestion referring to another question that addresses how to configure the login on a particular (external to a laptop) screen doesn't really cut it here--though it might well be related. The part of my question that is not answered is this:
My config involves a non-integer scaling of one screen, hence, the graphical utility, which only offers 100% or 200% scaling) is not usable, hence, I cannot use it to get a monitors.xml file.
In consequence, it might be that if someone can tell me how to hand-configure monitors.xml (which my searches so far lead me to believe is essentially undocumented), that would likely move me forward.
I will further note that the existing monitors.xml file in my system is hugely cluttered and therefore confusing. This is probably because I've had innumerable different monitors, and combinations of monitors, on this system over several years, and I get the impression that every single previous monitor is still listed in there. Is it safe perhaps to delete it, use the graphical tool to create a new (cleaner) one, and go from there? I hesitate lest I totally wreck my system!
Edit 2: I have noticed another problem with the current configuration: if the cursor from this plymouth boot-screen thing is on screen (i.e. "normally", the only exception being when I move the mouse to the extreme right edge and it disappears off the visible region), then after I log in, that cursor remains visible over the top of everything else! Took me ages to realize what it was, but with this poking around, I have finally become aware, and it seems to be 100% repeatable. I have no idea if this is related to my larger issue (I suspect not), but it is making me wonder if a better solution (I don't need "fast startup") might be do disable plymouth's login feature and instead use XDM (which I used to know how to configure in about 1994 ;) but perhaps is non-viable, or not the same as it was, these days?
