#include "imgui_plot.h"

namespace ImGui
{
	bool is_inside_area(const ImVec2& P, const ImVector<ImVec2>& V)
	{
		size_t cn = 0; // the crossing number counter
		size_t n = V.size();

		if (n < 3) return false;

		size_t i = 0;
		size_t j = 1;

		while (i < n) {
			if (((V[i].y <= P.y) && (V[j].y > P.y)) || ((V[i].y > P.y) && (V[j].y <= P.y))) {
				float vt = (float)(P.y - V[i].y) / (V[j].y - V[i].y);
				if (P.x < V[i].x + vt * (V[j].x - V[i].x)) { // P.x < intersect
					++cn; // a valid crossing of y=P.y right of P.x
				}
			}
			++i;
			j = (i + 1) % n;
		}

		return cn % 2 != 0; // false if even (out), and true if odd (in)
	}
}