/* check if (i, i + 2) is a diagonal */
static int dpd_isdiagonal(int i, int ip2, Ppoint_t ** pointp, int pointn)
{
int ip1, im1, j, jp1, res;
/* neighborhood test */
ip1 = (i + 1) % pointn;
im1 = (i + pointn - 1) % pointn;
/* If P[i] is a convex vertex [ i+1 left of (i-1,i) ]. */
if (dpd_ccw(pointp[im1], pointp[i], pointp[ip1]) == ISCCW)
res = (dpd_ccw(pointp[i], pointp[ip2], pointp[im1]) == ISCCW) &&
(dpd_ccw(pointp[ip2], pointp[i], pointp[ip1]) == ISCCW);
/* Assume (i - 1, i, i + 1) not collinear. */
else
res = ((dpd_ccw(pointp[i], pointp[ip2], pointp[ip1]) == ISCW)
);
/*
&&
(dpd_ccw (pointp[ip2], pointp[i], pointp[im1]) != ISCW));
*/
if (!res) {
return FALSE;
}
/* check against all other edges */
for (j = 0; j < pointn; j++) {
jp1 = (j + 1) % pointn;
if (!((j == i) || (jp1 == i) || (j == ip2) || (jp1 == ip2)))
if (dpd_intersects
(pointp[i], pointp[ip2], pointp[j], pointp[jp1])) {
return FALSE;
}
}
return TRUE;
}
static int dpd_between (Ppoint_t * pa, Ppoint_t * pb, Ppoint_t * pc) {
Ppoint_t pba, pca;
pba.x = pb->x - pa->x, pba.y = pb->y - pa->y;
pca.x = pc->x - pa->x, pca.y = pc->y - pa->y;
if (dpd_ccw (pa, pb, pc) != ISON)
return FALSE;
return (pca.x * pba.x + pca.y * pba.y >= 0) &&
(pca.x * pca.x + pca.y * pca.y <= pba.x * pba.x + pba.y * pba.y);
}
/* line to line intersection */
static int dpd_intersects (Ppoint_t *pa, Ppoint_t *pb, Ppoint_t *pc, Ppoint_t *pd) {
int ccw1, ccw2, ccw3, ccw4;
if (dpd_ccw(pa, pb, pc) == ISON || dpd_ccw (pa, pb, pd) == ISON ||
dpd_ccw (pc, pd, pa) == ISON || dpd_ccw (pc, pd, pb) == ISON) {
if (dpd_between (pa, pb, pc) || dpd_between (pa, pb, pd) ||
dpd_between (pc, pd, pa) || dpd_between (pc, pd, pb))
return TRUE;
} else {
ccw1 = (dpd_ccw (pa, pb, pc) == ISCCW) ? 1 : 0;
ccw2 = (dpd_ccw (pa, pb, pd) == ISCCW) ? 1 : 0;
ccw3 = (dpd_ccw (pc, pd, pa) == ISCCW) ? 1 : 0;
ccw4 = (dpd_ccw (pc, pd, pb) == ISCCW) ? 1 : 0;
return (ccw1 ^ ccw2) && (ccw3 ^ ccw4);
}
return FALSE;
}
