Function VHTightenHull

src/openboardview/vectorhulls.cpp:196–239

}

int VHTightenHull(ImVec2 hull[], int n, double threshold) {
	// theory: circle the hull, compare 3 points at a time, if the mid point is
	// sub-angular then make it equal the first point and move to the 3rd.
	int i, ni;
	ImVec2 *a, *b, *c;
	double a1, a2, ad;
	// First cycle, we look for sub-threshold 2-segment runs
	for (i = 0; i < n; i++) {
		a = &(hull[i]);
		b = &(hull[(i + 1) % n]);
		c = &(hull[(i + 2) % n]);

		a1 = VHAngleToX(*a, *b);
		a2 = VHAngleToX(*b, *c);
		if (a1 > a2)
			ad = a1 - a2;
		else
			ad = a2 - a1;

		if (ad < threshold) {
			//			fprintf(stderr,"angle below threshold
			//(%0.2f)\n", ad);
			*b = *a;
		}
	} // end first cycle

	// Second cycle, we compact the hull
	int output_index = 0;
	i                = 0;
	while (i < n) {
		ni = (i + 1) % n;
		if ((hull[i].x == hull[ni].x) && (hull[i].y == hull[ni].y)) {
			// match found, discard one
			i++;
			continue;
		}

		hull[output_index] = hull[i];
		output_index++;
		i++;
	}

	return output_index;
}

bool GetIntersection(ImVec2 p0, ImVec2 p1, ImVec2 p2, ImVec2 p3, ImVec2 *i) {