#include "gwin.user.h"
int seed = 0x7f03;
float random();
double ran();
int randseed = 345732;
main()
{
int ix,iy,xold,yold,event,xanchor,yanchor;
char key = '\0';


   ustart("high2",0.,640.,0.,400.);

   upset("colo",1.0);
   uprint(10.,90.,"Press left mouse button, hold, drag, release...");

   uset("comp");

   uset("ncli");
   BNDRYOFF(rport1);   /* BNDRYOFF is important! */
   while (1==1){
      while(key != 'a'){
         uigrina(&ix,&iy,&event,&key);
      }
      RectFill(rport1,ix-10,iy-10,ix,iy);
      xold = ix;
      yold = iy;

      while (key != 'A'){
         uigrina(&ix,&iy,&event,&key);
         randomdraw();
         if(ix != xold || iy != yold){
            RectFill(rport1,xold-10,yold-10,xold,yold);
            RectFill(rport1,ix-10,iy-10,ix,iy);
            xold = ix;
            yold = iy;
         }
      }
   }
   uend();
}

randomdraw()
{
int ix,iy;

   ix = 630.0*random(&seed);
   iy = 380.0*random(&seed);
   RectFill(rport1,ix+5,iy+15,ix+7,iy+17);
}

/* Note, the Manx "ran()" function appears to provide very             */
/* low precision results that are obvious on the screen.  The          */
/* following random number generator is an improvement and             */
/* sufficient for this demomstration.  You might wish to recompile     */
/* using the "ran()" function instead of the "random()" function       */
/* and observe the unwanted "order" that appears in the distribution.  */

float random(ix)
   int *ix;

/*     This routine adapted from page 227 of Simulation and  */
/*     Modeling Analysis, Law and Kelton, 1982.              */

{
   float rand;
   int xhi,xalo,leftlo,fhi,k;
   int a   = 16807;
   int b15 = 32768;
   int b16 = 65536;
   int p   = 2147483647;

   xhi = *ix/b16;
   xalo = (*ix-xhi*b16)*a;
   leftlo = xalo/b16;
   fhi = xhi*a+leftlo;
   k = fhi/b15;
   *ix = (((xalo-leftlo*b16)-p)+(fhi-k*b15)*b16)+k;
   if( *ix < 0 ) *ix = *ix + p;

   rand = *ix * 4.656612875e-10;

   return(rand);
}