On 24/02/2015 03:57, Michael DePaulo wrote:
I am trying to port this feature of VcXsrv (and XMing also I think) to
Cygwin XLaunch:
https://sourceforge.net/p/vcxsrv/code/ci/460182676a960385dff96c1563f781213060f6fc/
Attached is my WIP patch. (I know it needs the comments updated for main.cc).
There's a bug in main.cc that is causing this to happen when -1 is specified:
http://imgur.com/Jv4tpip
Protip: Ctrl-c works on MessageBox dialogs to copy their contents.
Thanks for looking into this.
Unfortunately, this turns into a non-trivial amount of work.
The upstream design is that -displayfd introduces a file descriptor that
the child X server process inherits, to which it will write it's display
number.
(This fd will be one end of a pipe which the parent process has opened,
and it will read the display number from the fd for the other end)
In the VcXsrv implementation, instead a handle to some shared memory is
used to pass the display number back. (I guess a Windows anonymous pipe
would have worked just as well, but possibly this is simpler to implement).
So, you will need to re-write the changes to main.cc to create a pipe
(using pipe()), pass the write fd using -displayfd, and read the diplay
number from the read fd.
Even after you've done this, I'm not 100% sure that cygwin pipes are
successfully propagated across CreateProcess(). I have a vague memory
this is where I got stuck when I last looked at this, but I'm not sure
I'd noticed that CreateProcess() is being invoked with
bInheritHandles=FALSE.
I found my old (non-working) attempt at implementing this [1], which
might help you a bit.
[1]
https://github.com/jon-turney/xlaunch/commit/b3fc02fcc9ac43224137963e2aba39abb88608da
--
Jon TURNEY
Volunteer Cygwin/X X Server maintainer
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