Listing 7

// custom_dlg.h
#include <win32gui/window.hpp>
struct custom_dlg 
     : win32::gui::wnd_extend<win32::gui::dialog,custom_dlg> {
  static int dialog_id();
};
// custom_dlg.cpp
#include "custom_dlg.h"
#include <win32gui/event_handler.hpp>
using namespace win32::gui;

// resource.h is included only in the source file!
#include "resource.h"

struct custom_handler
    : event_handler<custom_handler,dialog,custom_dlg> {
   // ...
};
int custom_dlg::dialog_id() { return IDD_custom; }