#!/usr/bin/perl -w                                                                   

use warnings ;
use strict ;  
use lib ('blib') ;
use Tk ;          
# OpenGL: need r:all for glGetIntegerv_p, need :old for glpOpen Window
use OpenGL qw(:all :old) ;                                            

my $arg = shift ;

my $MW = new MainWindow ;

# craps out if $border = 0
my $border = 1 ;          
my ( $w, $h ) = ( 100, 100 ) ;
my $glwin ;                   
my @attributes = [ GLX_RGBA, GLX_DOUBLEBUFFER, GLX_DEPTH_SIZE, 1 ] ;

my $id = $MW->WindowId ;
my $depth = glGetIntegerv_p( GL_DEPTH_BITS ) ;
print "Depth Before = $depth\n" ;             

$glwin = glpOpenWindow
    (                 
    x => $border, y => $border,
    width => $w, height => $h, 
    parent => $$id             
    ) if $arg eq 'A' ;         
$glwin = glpOpenWindow         
    (                          
    x => $border, y => $border,
    width => $w, height => $h, 
    parent => $$id,            
    attributes => \@attributes 
    ) if $arg eq 'B' ;
$glwin = glpcOpenWindow
    (
    $border, $border,
    $w, $h,
    $$id,
    0,
    \@attributes
    ) if $arg eq 'C' ;

$depth = glGetIntegerv_p( GL_DEPTH_BITS ) ;
print "Depth After = $depth\n" ;

##</code><code>##

Depth Before = 2
Depth After = 0

##</code><code>##

Depth Before = 2
Not a valid parameter to glpOpenWindow: `attributes'
No visual! at /usr/lib/perl5/OpenGL.pm line 6049.

##</code><code>##

Depth Before = 2
X Error of failed request:  BadValue (integer parameter out of range for operation)
  Major opcode of failed request:  1 (X_CreateWindow)
  Value in failed request:  0x2b1af80
  Serial number of failed request:  26
  Current serial number in output stream:  28