Faire une zone de dessin avec cairo

    #include <cairo.h>
    #include <gtk/gtk.h>
     
     
    double coordx[100];
    double coordy[100];
     
    int count = 0;
     
    static gboolean
    on_expose_event(GtkWidget *widget,
    GdkEventExpose *event,
    gpointer data)
    {
    cairo_t *cr;
     
    cr = gdk_cairo_create(widget->window);
     
    cairo_set_source_rgb(cr, 0, 0, 0);
    cairo_set_line_width (cr, 0.5);
     
    int i, j;
    for ( i = 0; i <= count - 1; i++ ) {
    for ( j = 0; j <= count -1; j++ ) {
    cairo_move_to(cr, coordx[i], coordy[i]);
    cairo_line_to(cr, coordx[j], coordy[j]);
    }
    }
     
    count = 0;
    cairo_stroke(cr);
    cairo_destroy(cr);
     
    return FALSE;
    }
     
    gboolean clicked(GtkWidget *widget, GdkEventButton *event,
    gpointer user_data)
    {
    if (event->button == 1) {
    coordx[count] = event->x;
    coordy[count++] = event->y;
    }
     
    if (event->button == 3) {
    gtk_widget_queue_draw(widget);
    }
     
    return TRUE;
    }
     
     
    int main (int argc, char *argv[])
    {
     
    GtkWidget *window;
     
    gtk_init(&argc, &argv);
     
    window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
     
    gtk_widget_add_events (window, GDK_BUTTON_PRESS_MASK);
     
    g_signal_connect(window, "expose-event",
    G_CALLBACK(on_expose_event), NULL);
    g_signal_connect(window, "destroy",
    G_CALLBACK(gtk_main_quit), NULL);
    g_signal_connect(window, "button-press-event",
    G_CALLBACK(clicked), NULL);
     
    gtk_window_set_position(GTK_WINDOW(window), GTK_WIN_POS_CENTER);
    gtk_window_set_title(GTK_WINDOW(window), "lines");
    gtk_window_set_default_size(GTK_WINDOW(window), 400, 300);
    gtk_widget_set_app_paintable(window, TRUE);
     
    gtk_widget_show_all(window);
     
    gtk_main();
     
    return 0;
    }