/* xlock-gc.c --- xscreensaver compatibility layer for xlockmore GL modules.
 * xscreensaver, Copyright (c) 1997 Jamie Zawinski <jwz@netscape.com>
 *
 * 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.  No representations are made about the suitability of this
 * software for any purpose.  It is provided "as is" without express or 
 * implied warranty.
 *
 * This file, along with xlockmore.h, make it possible to compile an xlockmore
 * GL module into a standalone program, and thus use it with xscreensaver.
 * By Jamie Zawinski <jwz@netscape.com> on 31-May-97.
 */

#include <stdio.h>
#include "screenhack.h"
#include "xlockmoreI.h"

#include <GL/gl.h>
#include <GL/glx.h>

/* Gag -- we use this to turn X errors from glXCreateContext() into
   something that will actually make sense to the user.
 */
static XErrorHandler orig_ehandler = 0;
static Bool got_error = 0;

static int
BadValue_ehandler (Display *dpy, XErrorEvent *error)
{
  if (error->error_code == BadValue)
    {
      got_error = True;
      return 0;
    }
  else
    return orig_ehandler (dpy, error);
}


GLXContext
init_GL(ModeInfo * mi)
{
  Display *dpy = mi->dpy;
  Window window = mi->window;
  Screen *screen = mi->xgwa.screen;
  Visual *visual = mi->xgwa.visual;
  GLXContext glx_context = 0;
  XVisualInfo vi_in, *vi_out;
  int out_count;

  vi_in.screen = screen_number (screen);
  vi_in.visualid = XVisualIDFromVisual (visual);
  vi_out = XGetVisualInfo (dpy, VisualScreenMask|VisualIDMask,
			   &vi_in, &out_count);
  if (! vi_out) abort ();

  {
    XSync (dpy, False);
    orig_ehandler = XSetErrorHandler (BadValue_ehandler);
    glx_context = glXCreateContext (dpy, vi_out, 0, GL_TRUE);
    XSync (dpy, False);
    XSetErrorHandler (orig_ehandler);
    if (got_error)
      glx_context = 0;
  }

  XFree((char *) vi_out);

  if (!glx_context)
    {
      fprintf(stderr, "%s: couldn't create GL context for visual 0x%x.\n",
	      progname, (unsigned int) XVisualIDFromVisual (visual));
      exit(1);
    }

  glXMakeCurrent (dpy, window, glx_context);

  {
    GLboolean rgba_mode = 0;
    glGetBooleanv(GL_RGBA_MODE, &rgba_mode);
    if (!rgba_mode)
      {
	glIndexi (WhitePixelOfScreen (screen));
	glClearIndex (BlackPixelOfScreen (screen));
      }
  }

  return (glx_context);
}


Visual *
get_gl_visual (Screen *screen, char *name, char *class)
{
  char *string = get_string_resource (name, class);
  XVisualInfo *vi = 0;
  Bool done_once = False;

 AGAIN:
  if (!string || !*string ||
      !strcmp (string, "best") ||
      !strcmp (string, "color") ||
      !strcmp (string, "default"))
    {
      Display *dpy = DisplayOfScreen (screen);
      int screen_num = screen_number (screen);
      int attrs[20];
      int i = 0;
      Bool dbuf_p = !get_boolean_resource ("noBuffer", "NoBuffer");

      done_once = True;

      attrs[i++] = GLX_RGBA;
      attrs[i++] = GLX_RED_SIZE;   attrs[i++] = 1;
      attrs[i++] = GLX_GREEN_SIZE; attrs[i++] = 1;
      attrs[i++] = GLX_BLUE_SIZE;  attrs[i++] = 1;
      attrs[i++] = GLX_DEPTH_SIZE; attrs[i++] = 1;
      if (dbuf_p)
	attrs[i++] = GLX_DOUBLEBUFFER;
      attrs[i++] = 0;

      vi = glXChooseVisual (dpy, screen_num, attrs);
      if (vi) goto DONE;

      /* Try without double-buffering. */
      attrs[i - 1] = 0;
      vi = glXChooseVisual (dpy, screen_num, attrs);
      if (vi) goto DONE;

      /* Try mono. */
      i = 0;
      if (dbuf_p)
	attrs[i++] = GLX_DOUBLEBUFFER;
      attrs[i++] = 0;
      vi = glXChooseVisual (dpy, screen_num, attrs);
      if (vi) goto DONE;

      /* Try mono without double-buffering. */
      attrs[0] = 0;
      vi = glXChooseVisual (dpy, screen_num, attrs);
    }

 DONE:
  {
    Visual *v;
    if (vi)
      {
	v = vi->visual;
	XFree (vi);
      }
    else
      {
	v = get_visual (screen, string, False, True);
	if (!v)
	  {
	    if (done_once)
	      v = DefaultVisualOfScreen (screen);
	    else
	      {
		free (string);
		string = 0;
		goto AGAIN;
	      }
	  }
      }

    free (string);
    return v;
  }
}
