example_menu.cpp

#include <nana/gui.hpp>
#include <nana/gui/widgets/button.hpp>
#include <nana/gui/widgets/menu.hpp>
#include <iostream> 

void on_menu_item(nana::menu::item_proxy& ip)
{
        std::size_t index = ip.index(); //Get the index of the clicking item.
    std::cout << "Menu item index:  " << index << std::endl; 
}

int main()
{
        using namespace nana;
        form fm;
    fm.caption(L"Popup the menu when right clicking the button");

        ;//We need a menu object
        menu mobj;
        mobj.append ( "Item 0", &on_menu_item);
        mobj.append_splitter();
        mobj.append ( "Item 1", &on_menu_item);

        ;//Now we need a button.
        button btn(fm, nana::rectangle(nana::point(10, 10), nana::size(100, 25)));
        btn.caption("Popup Menu");

        ;//Popup the menu when right clicking the button.
        //btn.events().click(menu_popuper(mobj)) ;

        ;//Or popuping the menu with a specified coordinate when any mouse button is clicked.
        btn.events().mouse_down( menu_popuper( mobj, btn, nana::point(100, 36),   mouse::any_button ));

        fm.show();
        exec(

#ifdef NANA_AUTOMATIC_GUI_TESTING

                1, 2, [&btn]() {click(btn); }
#endif

        );
}