Simplest GTK2 app for debugging

main.c

#include <gtk/gtk.h>

#define WIDTH 640
#define HEIGHT 480

int
main (int argc, char **argv)
{
    GtkWidget *window;

    gtk_init (&argc, &argv);

    window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
    gtk_window_set_default_size (GTK_WINDOW (window), WIDTH, HEIGHT);
    gtk_window_set_title (GTK_WINDOW (window), "Just a window");
    g_signal_connect (G_OBJECT (window), "destroy", gtk_main_quit, NULL);

    gtk_widget_show_all (window);
    gtk_main ();

    return 0;
}