trash.c

#include <stdio.h>
#include <stdlib.h>
#include <gtk/gtk.h>

/*Callback function in which reacts to the "response" signal. Be sure to place 
it before the function it is called in*/
static void
on_response(GtkDialog *dialog,
            gint response_id,
            gpointer user_data)
{
    /*For demonstration purposes, this will show the int value 
  of the response type*/
    g_print("response is %d\n", response_id);

    /*This will cause the dialog to be destroyed*/
    gtk_widget_destroy(GTK_WIDGET(dialog));
}

/*Callback function in which reacts to the "clicked" signal*/
static void
show_dialog(GtkButton *button,
            gpointer user_data)
{
    GtkWindow *window = user_data;
    GtkWidget *dialog;
    GtkWidget *content_area;
    GtkWidget *label;

    gint response_id;

    /*Create the dialog window. Modal windows prevent interaction with other 
  windows in the same application*/
    dialog = gtk_dialog_new_with_buttons("A Gtk+ Dialog",
                                         window,
                                         GTK_DIALOG_MODAL,
                                         GTK_STOCK_OK,
                                         GTK_RESPONSE_OK,
                                         NULL);

    /*Create a label and attach it to the content area of the dialog*/
    content_area = gtk_dialog_get_content_area(GTK_DIALOG(dialog));
    label = gtk_label_new("This demonstrates a dialog with a label");
    gtk_container_add(GTK_CONTAINER(content_area), label);

    /*The main purpose of this is to show dialog's child widget, label*/
    gtk_widget_show_all(dialog);

    /*Connecting the "response" signal from the user to the associated
  callback function*/
    g_signal_connect(GTK_DIALOG(dialog),
                     "response",
                     G_CALLBACK(on_response),
                     NULL);
}

static void
activate(GtkApplication *app,
         gpointer user_data)
{
    GtkWidget *window;
    GtkWidget *button;

    /*Create a window with a title and a default size*/
    window = gtk_application_window_new(app);
    gtk_window_set_title(GTK_WINDOW(window), "GNOME Button");
    gtk_window_set_default_size(GTK_WINDOW(window), 250, 50);

    /*Create a button with a label, and add it to the window*/
    button = gtk_button_new_with_label("Click Me");
    gtk_container_add(GTK_CONTAINER(window), button);

    /*Connecting the clicked signal to the callback*/
    g_signal_connect(GTK_BUTTON(button),
                     "clicked",
                     G_CALLBACK(show_dialog),
                     GTK_WINDOW(window));

    gtk_widget_show_all(window);
}

int main(int argc, char **argv)
{
    GtkApplication *app;
    int status;

    app = gtk_application_new("org.gtk.example", G_APPLICATION_FLAGS_NONE);
    g_signal_connect(app, "activate", G_CALLBACK(activate), NULL);
    status = g_application_run(G_APPLICATION(app), argc, argv);
    g_object_unref(app);

    return status;
}