Dock displayed on wrong display after going back to external monitors

[BenoitDuffez]

What Happened

I have an HP ProBook 640G2 with a docking station, on which I have two displayport external monitors (1 and 2) as well as the laptop monitor (3, numbered to indicate their physical organization).

When docked, 1 and 3 are "extended" desktops and 2 (the central one) is marked primary, so it has wingpanel and the dock (auto-hide).

Expected Behavior

When I undock, everything goes to the only available screen => works well.
When I dock, everything goes back to normal, except that the dock is triggered by a bezel "hit" of the cursor from monitor 1 only. I had expected to "hit" the bottom center screen (2) to trigger it. When "hitting" the bottom of monitor 1, the dock shows up as expected on monitor 2. I can't trigger the dock to show up when "hitting" the monitor 2 bottom.

Workaround: open the system settings, go to the dock options, and close. Dock is now triggered from a bottom "hit" of monitor 2.

This is not a big problem, but it definitely looks like a bug. I don't undock often so I'm not very annoyed.

Steps to Reproduce

1. Dock
2. Undock
3. Dock

Logs

Let me know what kind of additional information I can provide

Platform Information

Latest public release from stable repositories (5.1.7 according to /etc/*release).

[lenemter]

Closing because we've rewritten the positioning code in OS 8.