line drawing program [fltk]

Bjarne Stroustrup “Programming Principles and Practice Using C++”
Chapter 16 Drill 2
Using GUI library called FLTK (Fast Light Tool Kit, “full tick”).

Output:

[code language=”cpp”]
// Philipp Siedler
// Bjarne Stroustrup’s PP
// Chapter 16 Drill 2

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

// layout
constexpr int xmax = 600;
constexpr int ymax = 400;

struct Lines_window : Window {
Lines_window(Point xy, int w, int h, const string& title);
private:
// data
Open_polyline lines;

// widgets
Button next_button; // add (next_x, next_y) to lines
Button quit_button; // end program
In_box next_x;
In_box next_y;
Out_box xy_out;

// actions invoked by callbacks
void next();
void quit();

// callback functions
static void cb_next(Address, Address);
static void cb_quit(Address, Address);
};

Lines_window::Lines_window(Point xy, int w, int h, const string& title)
:Window(xy, w, h, title),
next_button(Point(x_max() – 150, 0), 70, 20, "Next point", cb_next),
quit_button(Point(x_max() – 70, 0), 70, 20, "Quit", cb_quit),
next_x(Point(x_max() – 310, 0), 50, 20, "next x:"),
next_y(Point(x_max() – 210, 0), 50, 20, "next y:"),
xy_out(Point(100, 0), 100, 20, "current (x,y):")
{
attach(next_button);
attach(quit_button);
attach(next_x);
attach(next_y);
attach(xy_out);
xy_out.put("no point");
lines.set_color(Color::black);
attach(lines);
}

void Lines_window::next()
{
int x = next_x.get_int();
int y = next_y.get_int();

lines.add(Point(x, y));

// update current position readout
ostringstream ss;
ss << ‘(‘ << x << ‘,’ << y << ‘)’;
xy_out.put(ss.str());

redraw();
}

void Lines_window::quit()
{
hide();
}

void Lines_window::cb_next(Address, Address pw)
{
reference_to<Lines_window>(pw).next();
}

void Lines_window::cb_quit(Address, Address pw)
{
reference_to<Lines_window>(pw).quit();
}

int main()
try
{
Lines_window win(Point(100, 100), xmax, ymax, "lines");
return gui_main();
}
catch (exception& e) {
cerr << "error: " << e.what() << ‘\n’;
keep_window_open();
return 1;
}

catch (…) {
cerr << "Unknown exception!\n";
keep_window_open();
return 2;
}
[/code]