Add image to button when pressed

Question

button1_on_image = Gtk::manage(new Gtk::Image{"button1_on.png"});   // Load icon
button1_off_image = Gtk::manage(new Gtk::Image{"button1_off.png"}); //   images
button1 = Gtk::manage(new Gtk::ToolButton{*button1_off_image});  // Create button
button1->set_tooltip_markup("Select one stick");                //   with image
button1->signal_clicked().connect(sigc::mem_fun(*this, 
    &Main_window::on_button1_click));
toolbar->append(*button1);

This is a snippet of code showing how I successfully make the button. The problem is that, when it is clicked I want "button1_on.png" to be shown instead of "button1_off.png", but I don't know how to do that.

Answer 1

Here is a code snippet that does what you want:

1. When the window is initially created, the button is "Off".
2. When the button is clicked, the button changes state to "On".

Note that this is a minimal example, so clicking again on the button will not change its state back to "On", but I will leave this part to you, if it is a requirement for you.

#include <gtkmm.h>

int main(int argc, char *argv[])
{
    auto app = Gtk::Application::create(argc, argv, "buttons.on.off");

    // Load images:
    Gtk::Image button1_on_image{"button1_on.png"};
    Gtk::Image button1_off_image{"button1_off.png"};

    // Create button:
    Gtk::ToolButton button1{button1_off_image};
    button1.set_tooltip_markup("Select one stick");

    // Create handler (as a lambda):
    const auto handler = [&button1, &button1_on_image, &button1_off_image]()
                         {
                             // We change to "on" here (when clicked):
                             button1.set_icon_widget(button1_on_image);

                             // We make it visible:
                             button1.show_all();
                         };

    button1.signal_clicked().connect(handler);

    // Add the button to the window.
    Gtk::Window window;
    window.add(button1);

    // Make the window visible:
    window.show_all();

    return app->run(window);
}

I made some simplifications to your snippet:

1. List item
2. I put everything on the stack (no new).
3. The handler is a lambda.

In my opinion, it makes the syntax clearer.