BSD 4_3_Reno release

[unix-history] / usr / src / lib / libplot / t4013 / arc.c

/*
* Copyright (c) 1980 Regents of the University of California.
* All rights reserved.  The Berkeley software License Agreement
* specifies the terms and conditions for redistribution.
*/

#ifndef lint
static char sccsid[] = "@(#)arc.c       5.2 (Berkeley) 6/23/85";
#endif not lint

int del = 20;
step(d){
       del = d;
}
arc(x,y,x0,y0,x1,y1){
       double pc;
       double sqrt();
       int flg,m,xc,yc,xs,ys,qs,qf;
       float dx,dy,r;
       char use;
       dx = x-x0;
       dy = y-y0;
       r = dx*dx+dy*dy;
       pc = r;
       pc = pc > 0 ? sqrt(pc) : 0;
       flg = pc/4;
       if(flg == 0)step(1);
       else if(flg < del)step(flg);
       xc = xs = x0;
       yc = ys = y0;
       move(xs,ys);
       if(x0 == x1 && y0 == y1)flg=0;
       else flg=1;
       qs = quad(x,y,x0,y0);
       qf = quad(x,y,x1,y1);
       if(abs(x-x1) < abs(y-y1)){
               use = 'x';
               if(qs == 2 || qs ==3)m = -1;
               else m=1;
       }
       else {
               use = 'y';
               if(qs > 2)m= -1;
               else m= 1;
       }
       while(1){
               switch(use){
               case 'x':       
                       if(qs == 2 || qs == 3)yc -= del;
                       else yc += del;
                       dy = yc-y;
                       pc = r-dy*dy;
                       xc = m*(pc > 0 ? sqrt(pc) : 0)+x;
                       if((x < xs && x >= xc) || ( x > xs && x <= xc) ||
                           (y < ys && y >= yc) || ( y > ys && y <=  yc) )
                       {
                               if(++qs > 4)qs=1;
                               if(qs == 2 || qs == 3)m= -1;
                               else m=1;
                               flg=1;
                       }
                       cont(xc,yc);
                       xs = xc; 
                       ys = yc;
                       if(qs == qf && flg == 1)
                               switch(qf){
                               case 3:
                               case 4: 
                                       if(xs >= x1)return;
                                       continue;
                               case 1:
                               case 2:
                                       if(xs <= x1)return;
                               }
                       continue;
               case 'y':       
                       if(qs > 2)xc += del;
                       else xc -= del;
                       dx = xc-x;
                       pc = r-dx*dx;
                       yc = m*(pc > 0 ? sqrt(pc) : 0)+y;
                       if((x < xs && x >= xc) || ( x > xs && x <= xc ) ||
                           (y < ys && y >= yc) || (y > ys && y <= yc) )
                       {
                               if(++qs > 4)qs=1;
                               if(qs > 2)m = -1;
                               else m = 1;
                               flg=1;
                       }
                       cont(xc,yc);
                       xs = xc; 
                       ys = yc;
                       if(qs == qf && flg == 1)
                               switch(qs){
                               case 1:
                               case 4:
                                       if(ys >= y1)return;
                                       continue;
                               case 2:
                               case 3:
                                       if(ys <= y1)return;
                               }
               }
       }
}
quad(x,y,xp,yp){
       if(x < xp)
               if(y <= yp)return(1);
               else return(4);
       else if(x > xp)
               if(y < yp)return(2);
               else return(3);
       else if(y < yp)return(2);
       else return(4);
}