import cairo
import gtk
import gtk.gdk

def move_window_to_parent(w, p):
    pwidth, pheight = p.window.get_size();
    px, py = p.window.get_position();

    width, height = w.window.get_size();
    x, y = w.window.get_position();

    nx = px + pwidth / 2 - width / 2;
    ny = py + pheight / 2 - height / 2;

    if x != nx or y != ny:
        w.window.move (nx, ny);
    w.window.restack(p.window, True);

def show_lightbox(w):
    lightbox = gtk.Window();
    lightbox.set_transient_for(w);
    lightbox.set_decorated(False);
    lightbox.set_position(gtk.WIN_POS_CENTER_ON_PARENT);
    lightbox.set_type_hint(gtk.gdk.WINDOW_TYPE_HINT_SPLASHSCREEN);
    lightbox.set_default_size(w.allocation.width,
                              w.allocation.height);
    w.connect("configure-event", lambda *args: move_window_to_parent (lightbox, w));
    lightbox.set_decorated(False);
    lightbox.set_app_paintable(True);
    lightbox.realize();
    lightbox.window.set_back_pixmap(None, True);
    lightbox.show();
    pixmap = gtk.gdk.Pixmap(lightbox.window,
                            w.allocation.width,
                            w.allocation.height, -1);
    cr = pixmap.cairo_create();
    cr.set_source_pixmap(w.window,
                         w.allocation.x,
                         w.allocation.y);
    cr.paint();
    cr.set_source_rgba(0.0, 0.0, 0.0, 0.5);
    cr.paint();
    lightbox.window.set_back_pixmap(pixmap, False);
    lightbox.window.clear();
    gtk.gdk.flush();

    return lightbox;

def show_message_dialog(l):
    m = gtk.MessageDialog(l, buttons=gtk.BUTTONS_OK)
    m.set_markup("Woo, subdialog");
    m.set_position(gtk.WIN_POS_CENTER_ON_PARENT);
    l.connect("configure-event", lambda *args: move_window_to_parent (m, l));
    m.run();
    gtk.main_quit();

def on_clicked(b, w):
    l = show_lightbox(w);
    show_message_dialog(l);

w = gtk.Window();
w.set_default_size(800, 600);
box = gtk.VBox();
w.add(box);
l = gtk.Label("I'm the installer");
box.add(l);

b = gtk.Button("Show dialog");
b.connect("clicked", on_clicked, w);
box.pack_start(b, expand=False);

w.show_all();


gtk.main();