_DEVELOPING A PORTABLE C++ GUI CLASS LIBRARY_
by Andreas Meyer

Example 1: 

class MyDialog : public ModalDialog
{
protected:
    DefPushButton   aOkButton;
public:
            MyDialog( Window* pParent );
    void    QuitDialog( DefPushButton* pButton );
}

MyDialog::MyDialog( Window* pParent ) :
          ModalDialog( pParent ),
          aOkButton( this )
{
    aOkButton.ChangeClickHdl( LINK( this, MyDialog::QuitDialog ) );
}

...