The elusive logic of multi-display ordering

Ceph92

Limp Gawd
Joined
Sep 17, 2019
Messages
130
I'm running into weird display ordering. Can someone explain what this thing wants from me?

I have an old dell laptop, two 2x monitor setups, and identical dell docking stations. The existing one is wired 2x DP->DVI, and output 1 is always the left, primary display. I set up a second dock (same model) in another room with 2x DP->HDMI and it works the same: output 1 goes to left monitor and is primary and output 2 goes to the left. I also tried a TB3 (display alt mode) multi-monitor adapter and that works the same way.

Going back to the 2nd docking station, I change to 2x DP->DP cables, and the monitor order is reversed. So the right monitor is primary, and win10 thinks it's the left display. I swap the cords between outputs 1/2 and reboot, and the same thing: the right display is STILL primary and windows thinks it's the left display. If I unplug the right monitor, then the left becomes primary, but it reverts as soon as I plug the right monitor back in.

I'd rather understand what logic the hardware is using and get it set up correctly. If I reverse the displays in windows, I'm worried it will throw off the configuration for the other dock and I'll have to do this every time I relocate the laptop.

I saw something similar happening with my desktop, where the geforce adapter would choose on its own which is the primary output, and resolved it just by trying a few different configurations. I was never sure what the rule actually was.

Ideas?
 
Last edited:

sethk

2[H]4U
Joined
May 3, 2005
Messages
2,051
You can set whatever monitor you want to be primary and drag the. left and right to correct where windows thinks they are relative to each other. As to the built in algorithm that tries to guess their order and position I have no idea.
 

sharknice

2[H]4U
Joined
Nov 12, 2012
Messages
3,111
My guess is it's based on what hardware was recognized by Windows first, until you manually adjust them.

If you go to display settings and click 'identify displays' it will give them numbers.

And if you had them all connected from the beginning it probably has to do with what your docking station considers the order of it's connectors.
 
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