#include <stdio.h>
#include <stdlib.h>

#include <X11/Xutil.h>

#include <GL/glx.h>

extern const char *__progname;

#include "findvis.h"

static void get_config(Display *disp, XVisualInfo *vi, int attr, int *valp)
{
 int e;

 e = glXGetConfig(disp,vi,attr,valp);
 switch (e)
  { case GLX_NO_EXTENSION:
       fprintf(stderr,"%s: no GLX extension support\n",__progname);
       exit(1);
       break;
    case GLX_BAD_SCREEN:
       fprintf(stderr,"%s: visual %#x is on nonexistent screen?\n",__progname,(unsigned int)vi->visualid);
       exit(1);
       break;
    case GLX_BAD_ATTRIBUTE:
       fprintf(stderr,"%s: bad attribute %d\n",__progname,attr);
       exit(1);
       break;
    case GLX_BAD_VISUAL:
       fprintf(stderr,"%s: non-GL visual\n",__progname);
       exit(1);
       break;
    case 0:
       break;
    default:
       fprintf(stderr,"%s: strange error %d from glXGetConfig\n",__progname,e);
       exit(1);
       break;
  }
}

XVisualInfo *find_visual(Display *disp)
{
 typedef struct vstat VSTAT;
 struct vstat {
   int inx;
   int rsize;
   int gsize;
   int bsize;
   int asize;
   int dsize;
   int arsize;
   int agsize;
   int absize;
   int aasize;
   } ;
 XVisualInfo *viv;
 int nvi;
 int i;
 int value;
 VSTAT vs;
 VSTAT bvs;

 viv = XGetVisualInfo(disp,0,0,&nvi);
 if (nvi < 1)
  { fprintf(stderr,"%s: no visuals?!\n",__progname);
    exit(1);
  }
 bvs.inx = -1;
 for (i=nvi-1;i>=0;i--)
  { get_config(disp,viv+i,GLX_USE_GL,&value);
    switch (value)
     { case True:
	  break;
       case False:
	  continue;
	  break;
       default:
	  fprintf(stderr,"%s: strange value %d from GLX_USE_GL on %#x\n",
		__progname,value,(unsigned int)viv[i].visualid);
	  exit(1);
	  break;
     }
    get_config(disp,viv+i,GLX_LEVEL,&value);
    if (value != 0) continue;
    get_config(disp,viv+i,GLX_RGBA,&value);
    if (value != True) continue;
    vs.inx = i;
    get_config(disp,viv+i,GLX_RED_SIZE,&vs.rsize);
    get_config(disp,viv+i,GLX_GREEN_SIZE,&vs.gsize);
    get_config(disp,viv+i,GLX_BLUE_SIZE,&vs.bsize);
    get_config(disp,viv+i,GLX_ALPHA_SIZE,&vs.asize);
    get_config(disp,viv+i,GLX_DEPTH_SIZE,&vs.dsize);
    get_config(disp,viv+i,GLX_ACCUM_RED_SIZE,&vs.arsize);
    get_config(disp,viv+i,GLX_ACCUM_GREEN_SIZE,&vs.agsize);
    get_config(disp,viv+i,GLX_ACCUM_BLUE_SIZE,&vs.absize);
    get_config(disp,viv+i,GLX_ACCUM_ALPHA_SIZE,&vs.aasize);
    if ( (vs.rsize < 4) ||
	 (vs.gsize < 4) ||
	 (vs.bsize < 4) ||
	 (vs.asize < 4) ||
	 (vs.dsize < 8) ||
	 (vs.arsize < 4) ||
	 (vs.agsize < 4) ||
	 (vs.absize < 4) ||
	 (vs.aasize < 4) ) continue;
    if ( (bvs.inx < 0) ||
	 ( (vs.rsize >= bvs.rsize) &&
	   (vs.gsize >= bvs.gsize) &&
	   (vs.bsize >= bvs.bsize) &&
	   (vs.asize >= bvs.asize) &&
	   (vs.dsize >= bvs.dsize) &&
	   (vs.arsize >= bvs.arsize) &&
	   (vs.agsize >= bvs.agsize) &&
	   (vs.absize >= bvs.absize) &&
	   (vs.aasize >= bvs.aasize) &&
	   ( vs.rsize+vs.gsize+vs.bsize+vs.asize >=
	     bvs.rsize+bvs.gsize+bvs.bsize+bvs.asize ) &&
	   ( vs.arsize+vs.agsize+vs.absize+vs.aasize >=
	     bvs.arsize+bvs.agsize+bvs.absize+bvs.aasize ) ) )
     { bvs = vs;
     }
  }
 if (bvs.inx < 0)
  { fprintf(stderr,"%s: can't find a suitable visual\n",__progname);
    exit(1);
  }
 return(viv+bvs.inx);
}