[Bug 52724] New: expose a stable interface to get the linux pid mapped to a wine pid

[WineHQ Bugzilla]

https://bugs.winehq.org/show_bug.cgi?id=52724

Bug ID: 52724
           Summary: expose a stable interface to get the linux pid mapped
                    to a wine pid
           Product: Wine
           Version: 7.4
          Hardware: x86-64
                OS: Linux
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: -unknown
          Assignee: [e-mail]
          Reporter: [e-mail]
      Distribution: ---

to get the x11 window id of a window handle inside wine, you can use 
`GetProp(win32_handle, "__wine_x11_whole_window");`.

but there is no equivalent function to get the linux pid of a wine process by
using its wine pid. it is useful when a windows app and linux app need to
interact with each other.
to check that the wine application is still running, or monitor its resource
usage etc.. the linux native app could use linux pid of the wine application.

Use Case:
I run Guild Was 2 in wine. and Guild Wars 2 shares live data of the player via
shared memory  called MumbleLink. unfortunately, shared memory of windows is
not exposed as shared memory of linux. so, i wrote a small app windows which
runs inside the same prefix of Guild Wars 2, and  copies that data to
z:\dev\shm\gw2link file which is in the linux path of /dev/shm/gw2link.

on Windows, there are Overlays (officially allowed) which make use of this data
to provide a wide variety of utilities to players. I am making a linux Overlay
and to get the position / size of the Guild Wars 2 Window, i need the x11
window id. as mentioned above, I already use the "__wine_x11_whole_window" to
get that and copy it to the /dev/shm/gw2link along with the other data. then,
linux native Overlay uses that file to get the window id and uses x11 to take
care of the rest.

But there are complex scenarios like multiple instances of gw2 running, and to
make it easy, gw2 writes is pid along with player data in the shared memory. we
use that pid to check if gw2 is running or other such things. and here's the
issue, gw2 writes the windows (wine) pid in the shared memory. and i have no
way of translating it to the mapped linux pid of that gw2 instance.

I am currently able to use _NET_WM_PID x11 property to get the pid of a gw2
window, but it is not actually required by the x11 spec, and its also not
immediately set when the game starts. so, it is sort of unreliable at the
moment.

so, I was hoping that wine could expose a function (or a property like
__wine_x11_whole_window) so that i could translate the wine pid to linux pid,
and provide that pid via /dev/shm/gw2link just like x11 window id.