How to disconnect a signal

Question

I made a program to calculate the area and volume of shapes from a window. Everything works, except one thing regarding the use of Gtk::Entry::signal_activate(). In the following code:

  sigc::connection c = elongueur.signal_activate().connect([this]() { calcul(); });
  switch (forme)
  {
  case 1: //carré
    cacheEntry();
    c.connected();
    labelForme.set_label(listeDeroulante.get_active_text());
    labelLongueur.set_label("longueur");
    break;
  case 2: //rectangle
    c.disconnect();
    elargeur.set_sensitive(true);
    labelForme.set_label(listeDeroulante.get_active_text());
    labelLongueur.set_label("longueur");
    labelLargeur.set_label("largeur");
    elongueur.signal_activate().connect([this]() { elargeur.grab_focus(); });
    elargeur.signal_activate().connect([this]() { calcul(); });
    break;

 // ...

if I start with option case 2 everything works fine. If I go through case 1 and then case 2, pressing the enter key shifts the focus to the next Gtk::Entry but also launches the calculation() function, which I'm trying to avoid. I think the Gtk::Entry::signal_activate() handler is not disconnected after passing through case 1, but I don't know why since I am calling sigc::connection::disconnect() when entering case 2.

How could I make this work?

Answer 1

First add this header. See documentation from sigc++

#include <sigc++/connection.h>

We have to disconnect signal and stop it

Declare in your own class

sigc::connection c;

then in your main programm we can do something like that

  switch (forme)
  {
  case 1: // carré
    cacheEntry();
    labelForme.set_label(listeDeroulante.get_active_text());
    labelLongueur.set_label("longueur");
    if (c.connected() == false)
    {
      c = elongueur.signal_activate().connect([this]() { calcul(); });
    }
    break;
  case 2: // rectangle
    c.disconnect();//disconnected signal
    elargeur.set_sensitive(true);
    labelForme.set_label(listeDeroulante.get_active_text());
    labelLongueur.set_label("longueur");
    labelLargeur.set_label("largeur");
    elongueur.signal_activate().connect([this]() { elargeur.grab_focus(); });
    elargeur.signal_activate().connect([this]() { calcul(); elargeur.signal_activate().emission_stop();/*stop signal*/ });
    break;