Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uunet!ns-mx!cadfx.ccad.uiowa.edu!koch
From: koch@cadfx.ccad.uiowa.edu (Peter Koch)
Newsgroups: comp.windows.x
Subject: Sharing window ID's between processes
Message-ID: <1956@ns-mx.uiowa.edu>
Date: 25 Jul 90 21:00:10 GMT
Sender: news@ns-mx.uiowa.edu
Reply-To: koch@cadfx.ccad.uiowa.edu (Peter Koch)
Organization: CAD-Research, U of Iowa, Iowa City, IA
Lines: 18


  I am having trouble getting an application program 
to draw into a window of another application. I get a
X Protocol error "not a valid window ID". 

  The program that creates the drawing window calls a function
which creates a pipe between the other program, forks the 
parent process and calls execvp to execute the drawing program.
The window ID is used as a command line option for the drawing program.
The other program is executed, opens the display and prints to the screen 
the window ID in question. It is identical to the window ID of the program 
which created the window. The drawing program attempts to retrieve
the window attributes of the window using XGetWindowAttributes but fails
to recognize the window ID.

What am I doing wrong? 

Is it even possible to share window ID's between different processes?