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From: mouse@lightning.mcrcim.mcgill.EDU (der Mouse)
Newsgroups: comp.windows.x
Subject: fork() and BadIDChoice
Message-ID: <9103060732.AA02341@lightning.McRCIM.McGill.EDU>
Date: 6 Mar 91 07:32:34 GMT
Sender: daemon@athena.mit.edu (Mr Background)
Organization: The Internet
Lines: 26

> I'm writing a Motif application which requires me to fork() and
> continue processing with the same windows & environment.  The first
> time I try to bring up a new window after the fork(), I get the
> following error:

> X Error of failed request:  BadIDChoice (invalid resource ID chosen for this connection)

[...]

> I think that I have to create a new connection to the original
> display... but I don't know how to do that.  (This is the deepest
> I've had to delve into Xlib.)

You are correct.  When a process with an X connection open fork()s, at
most one of the resulting two processes can do anything to the
connection (where XCloseDisplay counts as doing something).  One of the
processes should probably close the connection out from under Xlib,
with close(XConnectionNumber(dpy)), and *then* XCloseDisplay() (to free
up the Xlib data structures) and open a new connection.

How this relates to toolkits and higher layers I have no idea.

					der Mouse

			old: mcgill-vision!mouse
			new: mouse@larry.mcrcim.mcgill.edu