Advanced MFC Programming

Chapter 2. Menu
Because the popup menu is attached to variable CMenuDoc::m_menuModified, we need to detach it
before application exits. The best place of implementing this is in class MCMenu’s destructor, when the menu
object is about to be destroyed:
MCMenu::~MCMenu()
{
Detach();
}
Now we can compile the sample project and execute it. By executing command Edit | Insert Dynamic
Menu and expanding Dynamic Menu then selecting the first two menu items, we will see that both
selected and unselected states of them will be implemented by our own bitmaps.
Bitmap is not restricted to only indicating selected and normal menu states. With a little effort, we
could also use bitmap to implement other menu states: grayed, checked, and unchecked. This will make our
menu completely different from a menu implemented by plain text.
2.7 Changing the Whole Menu Dynamically
If we write MDI application, we can see that the main menu may change with different type of views.
Generally, when there is no client window opened, the mainframe menu will have only three sub-menus
(File, View, Help). After the user opens a client window, the mainframe menu will be replaced with a new
menu that has more sub-menus. Although we could call CMenu::ModifyMenu(…) to implement this, it is not
efficient because with this method, we have to the change menu items one by one. Actually, there is
another easy way to change the whole menu dynamically: we can prepare a new menu resource, use it to
replace the menu currently associated with the window at run time.
Class CWnd has a member function that can be used to set a window’s menu dynamically:
CWnd::SetMenu(…). The function has only one parameter, which is a CMenu type pointer. By using this
function, we can change an application’s mainframe menu at any time we want. Sample 2.7\Menu
demonstrates this technique. It is a standard SDI application generated by Application Wizard with all
default settings. In the sample, besides mainframe menu IDR_MAINFRAME, a new menu resource
IDR_MAINFRAME_ACTIVE is prepared in the application. This menu has some new sub-menus (Options,
Properties, Settings). For the purpose of demonstration, none of these sub-menus contains menu items.
The default menu will be changed to this menu after we execute File | New or File | Open command. If we
execute File | Close command from menu IDR_MAINFRAME_ACTIVE, the default menu will be resumed.
Three WM_COMMAND message handlers for commands ID_FILE_NEW, ID_FILE_OPEN and ID_FILE_CLOSE
are generated using class wizard. The member functions are named OnFileNew, OnFileOpen and
OnFileClose. In the first two functions, we change the mainframe menu to IDR_MAINFRAME_ACTIVE, and in
the third function, we change the menu back to IDR_MAINFRAME:
void CMenuDoc::OnFileNew()
{
CMenu menu;
}
menu.LoadMenu(IDR_MAINFRAME_ACTIVE);
AfxGetMainWnd()->SetMenu(&menu);
AfxGetMainWnd()->DrawMenuBar();
menu.Detach();
void CMenuDoc::OnFileOpen()
{
CMenu menu;
}
menu.LoadMenu(IDR_MAINFRAME_ACTIVE);
AfxGetMainWnd()->SetMenu(&menu);
AfxGetMainWnd()->DrawMenuBar();
menu.Detach();
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