[Bug 49766] New: Virtual desktop window is too big on wine 5.16

[WineHQ Bugzilla]

https://bugs.winehq.org/show_bug.cgi?id=49766

Bug ID: 49766
           Summary: Virtual desktop window is too big on wine 5.16
           Product: Wine
           Version: 5.16
          Hardware: x86-64
                OS: Linux
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: winex11.drv
          Assignee: [e-mail]
          Reporter: [e-mail]
                CC: [e-mail]
   Regression SHA1: aadae4d1ea173dfa30e09d6cc816bb174e35f90d
      Distribution: ArchLinux

I have three 1920x1080 monitors in a Xinerama setup with proprietary Nvidia
drivers.
wine 5.16 sometimes creates a virtual desktop that is larger than any of my
monitors (actually equal to the total size of my X screen), even when the
virtual desktop resolution is set to 1280x720.

Steps to reproduce:
 - Create a clean 32-bit wine prefix
 - Run winecfg, enable virtual desktop mode, set resolution to 1280x720
 - Run wineserver -w
 - Run winecfg again, it opens in a 4390x2160 virtual desktop window that
covers multiple monitors
 - Run wineserver -w
 - Run winecfg again, the virtual desktop is still 4390x2160

On a 64-bit prefix, these steps are less repeatable. Depending on timing the
second or third winecfg runs may run in a correctly sized window, and then stay
that way for all further runs. Some things change in
System\CurrentControlSet\Enum\DISPLAY\DEFAULT_MONITOR between the bad and
good winecfg runs, but I cannot reproduce the bad behavior by restoring the
entire wine prefix, so the change seems to be related to timing that is not
controlled for by wineserver -w.

A bisect points to commit aadae4d1ea173dfa30e09d6cc816bb174e35f90d as the first
bad commit, though I think this commit may have only uncovered an existing bug
rather than creating one.

Bad wine versions create a 4390x2160 window with "_NET_WM_STATE(ATOM) =
_NET_WM_STATE_MAXIMIZED_HORZ, _NET_WM_STATE_MAXIMIZED_VERT". Good wine versions
create a 1280x720 window with an empty/zeroed "_NET_WM_STATE(ATOM)".

Note: I see this message a lot on both wine 5.15 and wine 5.16:
01c4:err:winediag:is_broken_driver Broken NVIDIA RandR detected, falling back
to RandR 1.0. Please consider using the Nouveau driver instead.

Unfortunately, nouveau does not support my GTX 970, so I have no choice.