tpoly.c - plan9port - [fork] Plan 9 from user space
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       tpoly.c (1689B)
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            1 #include <u.h>
            2 #include <libc.h>
            3 #include <draw.h>
            4 
            5 static
            6 uchar*
            7 addcoord(uchar *p, int oldx, int newx)
            8 {
            9         int dx;
           10 
           11         dx = newx-oldx;
           12         /* does dx fit in 7 signed bits? */
           13         if((unsigned)(dx - -0x40) <= 0x7F)
           14                 *p++ = dx&0x7F;
           15         else{
           16                 *p++ = 0x80 | (newx&0x7F);
           17                 *p++ = newx>>7;
           18                 *p++ = newx>>15;
           19         }
           20         return p;
           21 }
           22 
           23 static
           24 void
           25 dopoly(int cmd, Image *dst, Point *pp, int np, int end0, int end1, int radius, Image *src, Point *sp, Drawop op)
           26 {
           27         uchar *a, *t, *u;
           28         int i, ox, oy;
           29 
           30         if(np == 0)
           31                 return;
           32         t = malloc(np*2*3);
           33         if(t == nil)
           34                 return;
           35         u = t;
           36         ox = oy = 0;
           37         for(i=0; i<np; i++){
           38                 u = addcoord(u, ox, pp[i].x);
           39                 ox = pp[i].x;
           40                 u = addcoord(u, oy, pp[i].y);
           41                 oy = pp[i].y;
           42         }
           43 
           44         _setdrawop(dst->display, op);
           45 
           46         a = bufimage(dst->display, 1+4+2+4+4+4+4+2*4+(u-t));
           47         if(a == 0){
           48                 free(t);
           49                 fprint(2, "image poly: %r\n");
           50                 return;
           51         }
           52         a[0] = cmd;
           53         BPLONG(a+1, dst->id);
           54         BPSHORT(a+5, np-1);
           55         BPLONG(a+7, end0);
           56         BPLONG(a+11, end1);
           57         BPLONG(a+15, radius);
           58         BPLONG(a+19, src->id);
           59         BPLONG(a+23, sp->x);
           60         BPLONG(a+27, sp->y);
           61         memmove(a+31, t, u-t);
           62         free(t);
           63 }
           64 
           65 void
           66 poly(Image *dst, Point *p, int np, int end0, int end1, int radius, Image *src, Point sp)
           67 {
           68         dopoly('p', dst, p, np, end0, end1, radius, src, &sp, SoverD);
           69 }
           70 
           71 void
           72 polyop(Image *dst, Point *p, int np, int end0, int end1, int radius, Image *src, Point sp, Drawop op)
           73 {
           74         dopoly('p', dst, p, np, end0, end1, radius, src, &sp, op);
           75 }
           76 
           77 void
           78 fillpoly(Image *dst, Point *p, int np, int wind, Image *src, Point sp)
           79 {
           80         dopoly('P', dst, p, np, wind, 0, 0, src, &sp, SoverD);
           81 }
           82 
           83 void
           84 fillpolyop(Image *dst, Point *p, int np, int wind, Image *src, Point sp, Drawop op)
           85 {
           86         dopoly('P', dst, p, np, wind, 0, 0, src, &sp, op);
           87 }