4.3BSD - /usr/src/new/X/xgedit/garc.c

   1: #include <X/mit-copyright.h>
   2: 
   3: /* Copyright    Massachusetts Institute of Technology    1984, 1985	*/
   4: 
   5: #include "gedit.h"
   6: 
   7: #ifndef lint
   8: static char *rcsid_garc_c = "$Header: garc.c,v 10.5 86/02/01 16:18:41 tony Rel $";
   9: #endif	lint
  10: 
  11: /* arc drawing routines */
  12: 
  13: double sqrt(),atan2(),sin(),cos();
  14: char *malloc();
  15: 
  16: /* construct a line object */
  17: gptr mline(x1,y1,x2,y2,next)
  18:   gptr next;
  19:   { register gptr p;
  20: 
  21:     if ((p = (gptr)malloc(sizeof(struct segment))) == NULL) {
  22:       msg("out of room!");
  23:       return(next);
  24:     }
  25:     p->s.type = SEGMENT;
  26:     p->s.next = next;
  27:     p->s.parent = NULL;
  28:     p->s.x1 = x1;
  29:     p->s.y1 = y1;
  30:     p->s.x2 = x2;
  31:     p->s.y2 = y2;
  32:     p->s.angle = 0;
  33:     p->s.cache = NULL;
  34:     return(p);
  35: }
  36: 
  37: /* rounds the double x off to an integer */
  38: int round(x)
  39:  double x;
  40:   { register int i;
  41:     if (x >= 0.0) i = x+0.5; else i = x-0.5;
  42:     return(i);
  43:   }
  44: 
  45: /* compute center from arc end point and radius */
  46: circcent(ang,fx,fy,tx,ty,xcp,ycp,rp)
  47:  int ang,fx,fy,tx,ty,*xcp,*ycp;
  48:  double *rp;
  49:   { double xx,yy,ss,dd,x1,y1;
  50: 
  51:     xx = tx - fx; yy = ty - fy;
  52:     dd = sqrt(xx*xx + yy*yy);   /* length of chord */
  53:     if (dd == 0) { *xcp = fx; *ycp = fy; *rp = 0; return; }
  54: 
  55:     /* radius of arc */
  56:     *rp = dd / (2.0 * sin(3.141592653 * ang / 2048.0));
  57: 
  58:     /* length of perpendicular to chord */
  59:     ss = sqrt((*rp)*(*rp) - dd*dd/4.0);
  60: 
  61:     if (ang > 1024) ss = -ss;
  62:     x1 = (tx + fx) / 2.0;   /* compute center point of chord */
  63:     y1 = (ty + fy) / 2.0;
  64:     x1 -= yy*ss/dd;     /* now compute center of circle */
  65:     y1 += xx*ss/dd;
  66: 
  67:     *xcp = round(x1); *ycp = round(y1);
  68: }
  69: 
  70: /* calculate new arc list */
  71: newalist(p,xa,ya,xb,yb)
  72:   register struct segment *p;
  73:   { double xx,yy,aa,bb;
  74:     double ainc,r;
  75:     int ix,iy,xc,yc;
  76:     int wherex,wherey;
  77: 
  78:     if (p->cache != NULL) {
  79:       rmalist(p->cache);
  80:       p->cache = NULL;
  81:     }
  82: 
  83:     if (p->angle == 0) return;
  84:     circcent(p->angle,xa,ya,xb,yb,&xc,&yc,&r);
  85: 
  86:     if (r < 2.0) {
  87:       p->cache = mline(xa-1,ya-1,xa+1,ya-1,p->cache);
  88:       p->cache = mline(xa-1,ya,xa+1,ya,p->cache);
  89:       p->cache = mline(xa-1,ya+1,xa+1,ya+1,p->cache);
  90:       return;
  91:     }
  92: 
  93:     xx = xa-xc; yy = ya-yc;
  94:     aa = atan2(yy,xx);
  95:     xx = xb-xc; yy = yb-yc;
  96:     bb = atan2(yy,xx);
  97: 
  98:     /* put aa and bb into proper relationship */
  99: /*	if (p->angle <= 1024) {
 100: */    if (aa > bb) bb += 2*3.141592653;
 101: /*	} else {
 102: 	  if (bb > aa) aa += 2*3.141592653;
 103: 	}
 104: */
 105:     /* usually 32 lines/arc, but use enough to ensure that there would
 106: 	 * be at least 100 segments for a full circle.
 107: 	 */
 108:     ainc = (bb - aa)/32.0;
 109:     if (ainc > 0.628) ainc = 0.628;
 110:     else if (ainc < -0.628) ainc = -0.628;
 111: 
 112:     wherex = xa; wherey = ya;
 113:     while (1) {
 114:       ix = xc + r*cos(aa);
 115:       iy = yc + r*sin(aa);
 116:       p->cache = mline(wherex,wherey,ix,iy,p->cache);
 117:       wherex = ix; wherey = iy;
 118:       aa += ainc;
 119:       if ((ainc<0 && aa<=bb) || (ainc>=0 && aa>=bb)) break;
 120:     };
 121:     p->cache = mline(wherex,wherey,xb,yb,p->cache);
 122: }

Defined functions

Defined variables