>># 
>># Copyright 1990, 1991 by the Massachusetts Institute of Technology and
>># UniSoft Group Limited.
>># 
>># Permission to use, copy, modify, distribute, and sell this software and
>># its documentation for any purpose is hereby granted without fee,
>># provided that the above copyright notice appear in all copies and that
>># both that copyright notice and this permission notice appear in
>># supporting documentation, and that the names of MIT and UniSoft not be
>># used in advertising or publicity pertaining to distribution of the
>># software without specific, written prior permission.  MIT and UniSoft
>># make no representations about the suitability of this software for any
>># purpose.  It is provided "as is" without express or implied warranty.
>># 
>># $XConsortium: dsplystr.m,v 1.13 92/06/11 15:58:55 rws Exp $
>># 
>>#
>>TITLE DisplayString CH02
>>ASSERTION A DisplayString-1
A call to DisplayString returns the string that was used as
the argument to the XOpenDisplay call that returned the
value used as the display argument.
>>STRATEGY
Open a connection using XOpenDisplay.
Obtain the display string using DisplayString.
Verify that the value of the string is the parameter used in XOpenDisplay.
Close the display using XCloseDisplay.
>>ASSERTION C DisplayString-2
If the system is POSIX compliant: When the argument passed
to the XOpenDisplay call that returned the value used as the
display argument was NULL, then a call to DisplayString
returns the value of the DISPLAY environment variable when
XOpenDisplay was called.
>>STRATEGY
Fork a child process using tet_fork.
In child :
  Exec the file "./Test1" with the environment variable DISPLAY set to the value of XT_DISPLAY config variable.
  Open the display "" using XOpenDisplay.
  Obtain the value of the display string using DisplayString.
  Obtain the value of the DISPLAY environment variable.
  Verify that the two strings are identical.
