polygon class point check [fltk]

Bjarne Stroustrup “Programming Principles and Practice Using C++”
Chapter 13 Exercise 18
Using GUI library called FLTK (Fast Light Tool Kit, “full tick”).

Output:

[code language=”cpp”]
// Philipp Siedler
// Bjarne Stroustrup’s PP
// Chapter 13 Exercise 18

#define _USE_MATH_DEFINES
#include "Simple_window.h"
#include "Graph.h"
#include <cmath>

using namespace Graph_lib;

ostream& operator<<(ostream& out, Point& a) {
out << "(" << a.x << "," << a.y << ")";
return out;
}

struct Poly : Closed_polyline
{
Poly(vector<Point> pts, Fl_Color linecolor)
: pts(pts), lc(linecolor)
{
if (pts.size() <= 2) {
error("Not enough points", pts.size());
}
else {
generate_points();
}
};

void generate_points();
void draw_lines() const;

private:
vector<Point> pts;
Fl_Color lc;
};

void Poly::generate_points()
{
for (int i = 0; i < pts.size(); i++) {
add(pts[i]);
}
};

void Poly::draw_lines() const
{
fl_color(lc);
Closed_polyline::draw_lines();
};

int main()
try
{
Point tl(100, 100);
Simple_window win(tl, 720, 400, "Simple Window");
Point center(win.x_max() / 2, win.y_max() / 2);

vector<Point> pts = { Point(100, 100), Point(150, 200) };

Poly p(pts, FL_RED);

win.attach(p);
win.wait_for_button();
}
catch (exception& e) {
cout << e.what() << endl;
return 1;
}
catch (…) {
cout << "Exiting" << endl;
return 2;
}
[/code]