Why can my window not reveive button_press signal?

[jerry <lvjieyong cis pku edu cn>]

Hi,all
I want to make a window, which will response when my mouse presses on it.
However I failed to do so when I rewrite the on_button_press_event function.
Who can explain it to me?
Thank you in advance.

The code is very simple and as following:

MAIN.CC
-----------------------------

#include <gtkmm/main.h>
#include "examplewindow.h"

int main(int argc, char *argv[])
{
  Gtk::Main kit(argc, argv);

  ExampleWindow window;
  Gtk::Main::run(window); //Shows the window and returns when it is closed.

  return 0;
}

MYWINDOW.H
----------------------------

#ifndef MY_WINDOW_H
#define MY_WINDOW_H

#include <gtkmm/window.h>


class mywindow:public Gtk::Window
{  
public:
    mywindow();
    ~mywindow();

protected:
    virtual bool on_button_press_event(GdkEventButton *e);

};

typedef mywindow gwindow;

#endif 

MYWINDOW.CC
---------------------------

#include "mywindow.h"
#include <gtkmm/messagedialog.h>

mywindow::mywindow() : Gtk::Window(Gtk::WINDOW_TOPLEVEL)
{
set_title("example");
set_default_size(450,500);
set_modal(false);
property_window_position().set_value(Gtk::WIN_POS_NONE);
set_resizable(true);
property_destroy_with_parent().set_value(false);
show_all_children();
}

mywindow::~mywindow()
{
}

bool mywindow::on_button_press_event(GdkEventButton* e)
{
bool ret_val = Window::on_button_release_event(e);

Gtk::MessageDialog dialog(*this, "Running...");
dialog.run();

return ret_val;
}