在gtkmm 教程 hello world 示例中，该libsigc++库在helloword.cc文件中使用：
#include "helloworld.h"
#include <iostream>
HelloWorld::HelloWorld()
: m_button("Hello World") // creates a new button with label "Hello World".
{
// Sets the border width of the window.
set_border_width(10);
// When the button receives the "clicked" signal, it will call the
// on_button_clicked() method defined below.
m_button.signal_clicked().connect(sigc::mem_fun(*this,
&HelloWorld::on_button_clicked));
// This packs the button into the Window (a container).
add(m_button);
// The final step is to display this newly created widget...
m_button.show();
}
但是，libsigc++从未包含在此文件中，但仍然可以正常工作。sigc命名空间从何而来？
编辑
helloworld.h：：
#ifndef GTKMM_EXAMPLE_HELLOWORLD_H
#define GTKMM_EXAMPLE_HELLOWORLD_H
#include <gtkmm/button.h>
#include <gtkmm/window.h>
class HelloWorld : public Gtk::Window
{
public:
HelloWorld();
virtual ~HelloWorld();
protected:
//Signal handlers:
void on_button_clicked();
//Member widgets:
Gtk::Button m_button;
};
#endif // GTKMM_EXAMPLE_HELLOWORLD_H