arc.c - vx32 - Local 9vx git repository for patches.
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arc.c (2607B)
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1 #include "u.h"
2 #include "lib.h"
3 #include "draw.h"
4 #include "memdraw.h"
5 #include "memlayer.h"
6
7 /*
8 * elarc(dst,c,a,b,t,src,sp,alpha,phi)
9 * draws the part of an ellipse between rays at angles alpha and alpha+phi
10 * measured counterclockwise from the positive x axis. other
11 * arguments are as for ellipse(dst,c,a,b,t,src,sp)
12 */
13
14 enum
15 {
16 R, T, L, B /* right, top, left, bottom */
17 };
18
19 static
20 Point corners[] = {
21 {1,1},
22 {-1,1},
23 {-1,-1},
24 {1,-1}
25 };
26
27 static
28 Point p00;
29
30 /*
31 * make a "wedge" mask covering the desired angle and contained in
32 * a surrounding square; draw a full ellipse; intersect that with the
33 * wedge to make a mask through which to copy src to dst.
34 */
35 void
36 memarc(Memimage *dst, Point c, int a, int b, int t, Memimage *src, Point sp, int alpha, int phi, int op)
37 {
38 int i, w, beta, tmp, c1, c2, m, m1;
39 Rectangle rect;
40 Point p, bnd[8];
41 Memimage *wedge, *figure, *mask;
42
43 if(a < 0)
44 a = -a;
45 if(b < 0)
46 b = -b;
47 w = t;
48 if(w < 0)
49 w = 0;
50 alpha = -alpha; /* compensate for upside-down coords */
51 phi = -phi;
52 beta = alpha + phi;
53 if(phi < 0){
54 tmp = alpha;
55 alpha = beta;
56 beta = tmp;
57 phi = -phi;
58 }
59 if(phi >= 360){
60 memellipse(dst, c, a, b, t, src, sp, op);
61 return;
62 }
63 while(alpha < 0)
64 alpha += 360;
65 while(beta < 0)
66 beta += 360;
67 c1 = alpha/90 & 3; /* number of nearest corner */
68 c2 = beta/90 & 3;
69 /*
70 * icossin returns point at radius ICOSSCALE.
71 * multiplying by m1 moves it outside the ellipse
72 */
73 rect = Rect(-a-w, -b-w, a+w+1, b+w+1);
74 m = rect.max.x; /* inradius of bounding square */
75 if(m < rect.max.y)
76 m = rect.max.y;
77 m1 = (m+ICOSSCALE-1) >> 10;
78 m = m1 << 10; /* assure m1*cossin is inside */
79 i = 0;
80 bnd[i++] = Pt(0,0);
81 icossin(alpha, &p.x, &p.y);
82 bnd[i++] = mulpt(p, m1);
83 for(;;) {
84 bnd[i++] = mulpt(corners[c1], m);
85 if(c1==c2 && phi<180)
86 break;
87 c1 = (c1+1) & 3;
88 phi -= 90;
89 }
90 icossin(beta, &p.x, &p.y);
91 bnd[i++] = mulpt(p, m1);
92
93 figure = nil;
94 mask = nil;
95 wedge = allocmemimage(rect, GREY1);
96 if(wedge == nil)
97 goto Return;
98 memfillcolor(wedge, DTransparent);
99 memfillpoly(wedge, bnd, i, ~0, memopaque, p00, S);
100 figure = allocmemimage(rect, GREY1);
101 if(figure == nil)
102 goto Return;
103 memfillcolor(figure, DTransparent);
104 memellipse(figure, p00, a, b, t, memopaque, p00, S);
105 mask = allocmemimage(rect, GREY1);
106 if(mask == nil)
107 goto Return;
108 memfillcolor(mask, DTransparent);
109 memimagedraw(mask, rect, figure, rect.min, wedge, rect.min, S);
110 c = subpt(c, dst->r.min);
111 memdraw(dst, dst->r, src, subpt(sp, c), mask, subpt(p00, c), op);
112
113 Return:
114 freememimage(wedge);
115 freememimage(figure);
116 freememimage(mask);
117 }