buttons

#include "Graph.h"       
#include "GUI.h"
#include "Window.h"
#include "std_facilities_lib_3.h"
#include <iostream>
#include <sstream>


using namespace Graph_lib;
using namespace std;


struct Lines_window : Window {
    Lines_window(Point xy, int w, int h, const string& title );
    Open_polyline lines;
private:
    Button next_button;        // add (next_x,next_y) to lines
    Button quit_button;
    In_box next_x;
    In_box next_y;
    Out_box xy_out;

    static void cb_next(Address, Address); // callback for next_button
    void next(); 
    static void cb_quit(Address, Address); // callback for quit_button
    void quit(); 
};


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);
    attach(lines);
}


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


void Lines_window::quit()
{
    hide();        // deletes the window
}


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



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:
    stringstream ss;
    ss << '(' << x << ',' << y << ')';
    xy_out.put(ss.str());

      redraw();
}


int main()
try {
    Lines_window win(Point(100,100),500,300,"lines");
    return gui_main();
}
catch(exception& e) {
    cerr << "exception: " << e.what() << '\n';
    return 1;
}
catch (...) {
    cerr << "Some exception\n";
    return 2;
}