ref: 34f5a8333090c5090e1d0b6ddbaf900d64340eea
dir: /sys/src/cmd/pic/arcgen.c/
#include <stdio.h> #include <math.h> #include "pic.h" #include "y.tab.h" void arc_extreme(double, double, double, double, double, double); int quadrant(double x, double y); obj *arcgen(int type) /* handles circular and (eventually) elliptical arcs */ { static double prevw = HT10; static double prevh = HT5; static double prevrad = HT2; static int dtox[2][4] ={ 1, -1, -1, 1, 1, 1, -1, -1 }; static int dtoy[2][4] ={ 1, 1, -1, -1, -1, 1, 1, -1 }; static int dctrx[2][4] ={ 0, -1, 0, 1, 0, 1, 0, -1 }; static int dctry[2][4] ={ 1, 0, -1, 0, -1, 0, 1, 0 }; static int nexthv[2][4] ={ U_DIR, L_DIR, D_DIR, R_DIR, D_DIR, R_DIR, U_DIR, L_DIR }; double dx2, dy2, ht, phi, r, d; int i, head, to, at, cw, invis, ddtype, battr; obj *p, *ppos; double fromx, fromy, tox, toy, fillval = 0; Attr *ap; prevrad = getfval("arcrad"); prevh = getfval("arrowht"); prevw = getfval("arrowwid"); fromx = curx; fromy = cury; head = to = at = cw = invis = ddtype = battr = 0; for (i = 0; i < nattr; i++) { ap = &attr[i]; switch (ap->a_type) { case TEXTATTR: savetext(ap->a_sub, ap->a_val.p); break; case HEAD: head += ap->a_val.i; break; case INVIS: invis = INVIS; break; case HEIGHT: /* length of arrowhead */ prevh = ap->a_val.f; break; case WIDTH: /* width of arrowhead */ prevw = ap->a_val.f; break; case RADIUS: prevrad = ap->a_val.f; break; case DIAMETER: prevrad = ap->a_val.f / 2; break; case CW: cw = 1; break; case FROM: /* start point of arc */ ppos = ap->a_val.o; fromx = ppos->o_x; fromy = ppos->o_y; break; case TO: /* end point of arc */ ppos = ap->a_val.o; tox = ppos->o_x; toy = ppos->o_y; to++; break; case AT: /* center of arc */ ppos = ap->a_val.o; curx = ppos->o_x; cury = ppos->o_y; at = 1; break; case UP: hvmode = U_DIR; break; case DOWN: hvmode = D_DIR; break; case RIGHT: hvmode = R_DIR; break; case LEFT: hvmode = L_DIR; break; case FILL: battr |= FILLBIT; if (ap->a_sub == DEFAULT) fillval = getfval("fillval"); else fillval = ap->a_val.f; break; } } if (!at && !to) { /* the defaults are mostly OK */ curx = fromx + prevrad * dctrx[cw][hvmode]; cury = fromy + prevrad * dctry[cw][hvmode]; tox = fromx + prevrad * dtox[cw][hvmode]; toy = fromy + prevrad * dtoy[cw][hvmode]; hvmode = nexthv[cw][hvmode]; } else if (!at) { dx2 = (tox - fromx) / 2; dy2 = (toy - fromy) / 2; phi = atan2(dy2, dx2) + (cw ? -PI/2 : PI/2); if (prevrad <= 0.0) prevrad = dx2*dx2+dy2*dy2; for (r=prevrad; (d = r*r - (dx2*dx2+dy2*dy2)) <= 0.0; r *= 2) ; /* this kludge gets around too-small radii */ prevrad = r; ht = sqrt(d); curx = fromx + dx2 + ht * cos(phi); cury = fromy + dy2 + ht * sin(phi); dprintf("dx2,dy2=%g,%g, phi=%g, r,ht=%g,%g\n", dx2, dy2, phi, r, ht); } else if (at && !to) { /* do we have all the cases??? */ tox = fromx + prevrad * dtox[cw][hvmode]; toy = fromy + prevrad * dtoy[cw][hvmode]; hvmode = nexthv[cw][hvmode]; } if (cw) { /* interchange roles of from-to and heads */ double temp; temp = fromx; fromx = tox; tox = temp; temp = fromy; fromy = toy; toy = temp; if (head == HEAD1) head = HEAD2; else if (head == HEAD2) head = HEAD1; } p = makenode(type, 7); arc_extreme(fromx, fromy, tox, toy, curx, cury); p->o_val[0] = fromx; p->o_val[1] = fromy; p->o_val[2] = tox; p->o_val[3] = toy; if (cw) { curx = fromx; cury = fromy; } else { curx = tox; cury = toy; } p->o_val[4] = prevw; p->o_val[5] = prevh; p->o_val[6] = prevrad; p->o_attr = head | (cw ? CW_ARC : 0) | invis | ddtype | battr; p->o_fillval = fillval; if (head) p->o_nhead = getfval("arrowhead"); dprintf("arc rad %g at %g %g from %g %g to %g %g head %g %g\n", prevrad, p->o_x, p->o_y, p->o_val[0], p->o_val[1], p->o_val[2], p->o_val[3], p->o_val[4], p->o_val[5]); return(p); } /*************************************************************************** bounding box of a circular arc Eric Grosse 24 May 84 Conceptually, this routine generates a list consisting of the start, end, and whichever north, east, south, and west points lie on the arc. The bounding box is then the range of this list. list = {start,end} j = quadrant(start) k = quadrant(end) if( j==k && long way 'round ) append north,west,south,east else while( j != k ) append center+radius*[j-th of north,west,south,east unit vectors] j += 1 (mod 4) return( bounding box of list ) The following code implements this, with simple optimizations. ***********************************************************************/ void arc_extreme(double x0, double y0, double x1, double y1, double xc, double yc) /* start, end, center */ { /* assumes center isn't too far out */ double r, xmin, ymin, xmax, ymax; int j, k; x0 -= xc; y0 -= yc; /* move to center */ x1 -= xc; y1 -= yc; xmin = (x0<x1)?x0:x1; ymin = (y0<y1)?y0:y1; xmax = (x0>x1)?x0:x1; ymax = (y0>y1)?y0:y1; r = sqrt(x0*x0 + y0*y0); if (r > 0.0) { j = quadrant(x0,y0); k = quadrant(x1,y1); if (j == k && y1*x0 < x1*y0) { /* viewed as complex numbers, if Im(z1/z0)<0, arc is big */ if( xmin > -r) xmin = -r; if( ymin > -r) ymin = -r; if( xmax < r) xmax = r; if( ymax < r) ymax = r; } else { while (j != k) { switch (j) { case 1: if( ymax < r) ymax = r; break; /* north */ case 2: if( xmin > -r) xmin = -r; break; /* west */ case 3: if( ymin > -r) ymin = -r; break; /* south */ case 4: if( xmax < r) xmax = r; break; /* east */ } j = j%4 + 1; } } } xmin += xc; ymin += yc; xmax += xc; ymax += yc; extreme(xmin, ymin); extreme(xmax, ymax); } quadrant(double x, double y) { if ( x>=0.0 && y> 0.0) return(1); else if( x< 0.0 && y>=0.0) return(2); else if( x<=0.0 && y< 0.0) return(3); else if( x> 0.0 && y<=0.0) return(4); else return 0; /* shut up lint */ }