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From: dl23+@andrew.cmu.edu (Damon Wayne Lipparelli)
Newsgroups: comp.sys.hp
Subject: xseethru
Message-ID: <UYFaawy00Vg6E1iV0k@andrew.cmu.edu>
Date: 14 Apr 89 21:59:24 GMT
Organization: Mathematics, Carnegie Mellon, Pittsburgh, PA
Lines: 60

Hello.  On the hp 835's there is a program called "xseethru" which allows you to
see the full color planes if you are running in the overlay planes.  I'm trying
to write something similar only on a more specific scale.  Does anyone know how
it works?

I've tried various things with varying results.  The program that comes the
closest is this one:

#include <stdio.h>
#include <starbase.c.h>

main(argc,argv)
int argc;
char **argv;
{
  int fd,f2;
  float p_l[2][3],r[3],p1[3],p2[3];
  int c;
  gescape_arg a,b;

  system("xwcreate -geometry =600x600 foo -bw 0");

  if ((fd = gopen("/dev/screen/foo",OUTINDEV,"sox11",0)) == -1)
    {
      fprintf(stderr,"Error:  Couldn't open window.\n");
      exit(-1);
    }

  if ((f2 = gopen("/dev/ocrt0",OUTDEV,"hp98731",0)) == -1)
    {
      fprintf(stderr,"Error:  Couldn't open overlay planes.\n");
      exit(-2);
    }

  inquire_sizes(fd,p_l,r,p1,p2,&c);
  background_color_index(fd,c-1);
  clear_control(fd,CLEAR_DISPLAY_SURFACE);
  clear_view_surface(fd);
  make_picture_current(fd);

  a.i[0] = FALSE;
  gescape(f2,SWITCH_SEMAPHORE,&a,&b);
  a.i[0] = c-1;
  gescape(f2,R_TRANSPARENCY_INDEX,&a,&b);
  a.i[0] = TRUE;
  gescape(f2,SWITCH_SEMAPHORE,&a,&b);

  while (1)
   ;
  gclose(fd);
  system("xwdestroy foo");
}

This opens a window which _does_ show the full color planes, but as soon as the
mouse is moved, or a key is hit, X disables the transparency.  What magic does
xseethru do?

Damon Lipparelli
Graphics Support Staff
Engineering Design Research Center