mjhjmtu

This issue is gonna seem like me being very pedantic, but it has real problematic effects on my system that I'll get into (besides just the minor one I'm about to mention).

XFCE loves to get my dual-monitor setup wrong. First it always assumes Mirrored, but that's not the topic of this question. It also always, whether on boot or after disconnecting either monitor, upon detecting both again and after I uncheck Mirrored, will want to put the physically left one to the virtual right and the physically right one to the virtual left, putting my main panel on the physically right monitor and making it so I have to move the mouse to the right edge of both monitors to get it over to the physically left one. This behavior has been consistent across several GPU changes with both GPUs involved, and even two different motherboards. I've been fixing it with a constant-looping userspace script that detects monitors and sets the right config with xrandr.

My left monitor is DVI and plugged into the main GPU Xorg is using, and my right monitor is HDMI and plugged into the much more powerful GPU I use with DRI_PRIME or in a virtual machine. The way my setup fits together, I actually can't change that arrangement.

I've noticed in XFCE's Display config, despite being the "Primary" both in this window and in xrandr, the DVI monitor is considered #2:

I checked xrandr and found an opposite numbering:

$ xrandr --listmonitors
Monitors: 2
 0: +*DVI-D-0 1920/531x1080/299+0+0 DVI-D-0
 1: +HDMI-A-0 1920/477x1080/268+1920+0 HDMI-A-0

But then in the whole current config, the supposed #1/1 is listed first for some reason:

$ xrandr --current
Screen 0: minimum 320 x 200, current 3840 x 1080, maximum 16384 x 16384
DisplayPort-0 disconnected (normal left inverted right x axis y axis)
HDMI-A-0 connected 1920x1080+1920+0 (normal left inverted right x axis y axis) 477mm x 268mm
 1920x1080 60.00*+ 50.00 59.94 59.99 
 1920x1080i 60.00 50.00 59.94 
 1600x1200 60.00 
 1680x1050 59.88 
 1280x1024 75.02 60.02 
 1440x900 59.90 
 1280x960 60.00 
 1366x768 59.79 
 1152x864 75.00 
 1280x720 60.00 50.00 59.94 
 1024x768 75.03 70.07 60.00 
 832x624 74.55 
 800x600 72.19 75.00 60.32 56.25 
 720x576 50.00 
 720x480 60.00 59.94 
 640x480 75.00 72.81 66.67 60.00 59.94 
 720x400 70.08 
DVI-D-0 connected primary 1920x1080+0+0 (normal left inverted right x axis y axis) 531mm x 299mm
 1920x1080 60.00*+
 1600x1200 60.00 
 1680x1050 59.88 
 1280x1024 75.02 60.02 
 1440x900 59.90 
 1280x960 60.00 
 1152x864 75.00 
 1024x768 75.03 70.07 60.00 
 832x624 74.55 
 800x600 72.19 75.00 60.32 56.25 
 640x480 75.00 72.81 66.67 59.94 
 720x400 70.08 

Another potential clue is: the HDMI GPU is actually above the DVI one in terms of PCIe slot positions, and currently has to be, and actually as soon as they became both AMD at the same time, my LGA-2011v3 motherboard now has a new bug where it often completely ignores the BIOS' primary GPU setting and tries to boot with HDMI as primary. I also can't change anything about this until I can afford to switch to Ryzen and a motherboard arrangement that lets me put the bigger GPU on the bottom.

My question: what causes these disparities, and how can I manipulate/fix them?

The reason: though most Linux programs go by that "primary" flag or that xrandr 0-1 numbering or, even more preferably, by which monitor my mouse is currently on, when it comes to where to put the GUI window, but some instead go by whatever that XFCE numbering is coming from in which my "first" monitor is actually the HDMI one on the right.

Most wine programs go by that wrong order. Usually, even when it's fullscreen, I can just move it to the other screen or emulate a virtual desktop, but the Battle.net Launcher is completely immune to these workarounds, and it's actually made it unuseable for me. Every menu in it, including the Settings, insists on opening at the very left edge of my HDMI monitor no matter what I do with $DISPLAY. The program even seems immune to the virtual desktop setting. And that makes most of these menus actually not load. I can't use them! And I can't find any help for this specific issue with Battle.net besides opening a bug report when I don't know how to reproduce it, nor any further help with how to force wine programs to use the current monitor or a specific monitor. So I have nothing left to do but at least know what's going on with these monitors, so at the very least I can figure out enough to submit that bug report, let alone fix this myself.

Is it possible to control which monitor is considered the primary monitor? sadly couldn't help me--it didn't go deep enough.
Setting primary monitor in XFCE? also didn't help.