main.cpp

#include <gtk/gtk.h>

static void on_activate(GtkApplication *app)
{
    // Create a new window
    GtkWidget *window = gtk_application_window_new(app);
    // Create a new button
    GtkWidget *button = gtk_button_new_with_label("Hello, GTK4 World!");
    // When the button is clicked, close the window passed as an argument
    g_signal_connect_swapped(button, "clicked", G_CALLBACK(gtk_window_close), window);
    gtk_window_set_child(GTK_WINDOW(window), button);
    gtk_window_present(GTK_WINDOW(window));
}

int main(int argc, char **argv)
{
    // Create a new application
    GtkApplication *app = gtk_application_new("com.example.GtkApplication",
                                              G_APPLICATION_FLAGS_NONE);
    g_signal_connect(app, "activate", G_CALLBACK(on_activate), NULL);
    return g_application_run(G_APPLICATION(app), argc, argv);
}