projects / unix-history / blame
| Commit | Line | Data |
|---|---|---|
| b059c7be DF |
1 | /* |
| 2 | * Copyright (c) 1980 Regents of the University of California. | |
| 3 | * All rights reserved. The Berkeley software License Agreement | |
| 4 | * specifies the terms and conditions for redistribution. | |
| 5 | */ | |
| 6 | ||
| 322fb4f6 | 7 | #ifndef lint |
| 910d8762 | 8 | static char sccsid[] = "@(#)arc.c 5.2 (Berkeley) %G%"; |
| b059c7be | 9 | #endif not lint |
| 322fb4f6 JK |
10 | |
| 11 | int del = 20; | |
| 12 | step(d){ | |
| 13 | del = d; | |
| 14 | } | |
| 15 | arc(x,y,x0,y0,x1,y1){ | |
| 16 | double pc; | |
| 17 | double sqrt(); | |
| 18 | int flg,m,xc,yc,xs,ys,qs,qf; | |
| 19 | float dx,dy,r; | |
| 20 | char use; | |
| 21 | dx = x-x0; | |
| 22 | dy = y-y0; | |
| 23 | r = dx*dx+dy*dy; | |
| 24 | pc = r; | |
| 910d8762 | 25 | pc = pc > 0 ? sqrt(pc) : 0; |
| 322fb4f6 JK |
26 | flg = pc/4; |
| 27 | if(flg == 0)step(1); | |
| 28 | else if(flg < del)step(flg); | |
| 29 | xc = xs = x0; | |
| 30 | yc = ys = y0; | |
| 31 | move(xs,ys); | |
| 32 | if(x0 == x1 && y0 == y1)flg=0; | |
| 33 | else flg=1; | |
| 34 | qs = quad(x,y,x0,y0); | |
| 35 | qf = quad(x,y,x1,y1); | |
| 36 | if(abs(x-x1) < abs(y-y1)){ | |
| 37 | use = 'x'; | |
| 38 | if(qs == 2 || qs ==3)m = -1; | |
| 39 | else m=1; | |
| 40 | } | |
| 41 | else { | |
| 42 | use = 'y'; | |
| 43 | if(qs > 2)m= -1; | |
| 44 | else m= 1; | |
| 45 | } | |
| 46 | while(1){ | |
| 47 | switch(use){ | |
| 48 | case 'x': | |
| 49 | if(qs == 2 || qs == 3)yc -= del; | |
| 50 | else yc += del; | |
| 51 | dy = yc-y; | |
| 52 | pc = r-dy*dy; | |
| 910d8762 | 53 | xc = m*(pc > 0 ? sqrt(pc) : 0)+x; |
| 322fb4f6 JK |
54 | if((x < xs && x >= xc) || ( x > xs && x <= xc) || |
| 55 | (y < ys && y >= yc) || ( y > ys && y <= yc) ) | |
| 56 | { | |
| 57 | if(++qs > 4)qs=1; | |
| 58 | if(qs == 2 || qs == 3)m= -1; | |
| 59 | else m=1; | |
| 60 | flg=1; | |
| 61 | } | |
| 62 | cont(xc,yc); | |
| 63 | xs = xc; | |
| 64 | ys = yc; | |
| 65 | if(qs == qf && flg == 1) | |
| 66 | switch(qf){ | |
| 67 | case 3: | |
| 68 | case 4: | |
| 69 | if(xs >= x1)return; | |
| 70 | continue; | |
| 71 | case 1: | |
| 72 | case 2: | |
| 73 | if(xs <= x1)return; | |
| 74 | } | |
| 75 | continue; | |
| 76 | case 'y': | |
| 77 | if(qs > 2)xc += del; | |
| 78 | else xc -= del; | |
| 79 | dx = xc-x; | |
| 80 | pc = r-dx*dx; | |
| 910d8762 | 81 | yc = m*(pc > 0 ? sqrt(pc) : 0)+y; |
| 322fb4f6 JK |
82 | if((x < xs && x >= xc) || ( x > xs && x <= xc ) || |
| 83 | (y < ys && y >= yc) || (y > ys && y <= yc) ) | |
| 84 | { | |
| 85 | if(++qs > 4)qs=1; | |
| 86 | if(qs > 2)m = -1; | |
| 87 | else m = 1; | |
| 88 | flg=1; | |
| 89 | } | |
| 90 | cont(xc,yc); | |
| 91 | xs = xc; | |
| 92 | ys = yc; | |
| 93 | if(qs == qf && flg == 1) | |
| 94 | switch(qs){ | |
| 95 | case 1: | |
| 96 | case 4: | |
| 97 | if(ys >= y1)return; | |
| 98 | continue; | |
| 99 | case 2: | |
| 100 | case 3: | |
| 101 | if(ys <= y1)return; | |
| 102 | } | |
| 103 | } | |
| 104 | } | |
| 105 | } | |
| 106 | quad(x,y,xp,yp){ | |
| 107 | if(x < xp) | |
| 108 | if(y <= yp)return(1); | |
| 109 | else return(4); | |
| 110 | else if(x > xp) | |
| 111 | if(y < yp)return(2); | |
| 112 | else return(3); | |
| 113 | else if(y < yp)return(2); | |
| 114 | else return(4); | |
| 115 | } |