Advanced MFC Programming

Chapter 2. Menu
}
AfxMessageBox("Pop up menu item 2");
void CMenuDoc::OnPopUpItem3()
{
AfxMessageBox("Pop up menu item 3");
}
void CMenuDoc::OnPopUpItem4()
{
AfxMessageBox("Pop up menu item 4");
}
With the above implementation, we are able to execute the commands contained in the right-click pop
up menu.
2.3 Updating Menu Dynamically
Sometimes it is desirable to change the contents of a menu dynamically. For example, if we create an
application that supports many commands, we may want to organize them into different groups. Sometimes
we want to enable a group of commands, sometimes we want to disable them.
Although we can handle UPDATE_COMMAND_UI message to enable or disable commands, sometimes it is
more desirable if we can remove the whole sub-menu instead of just graying the menu text. Actually, submenu
and menu item can all be modified dynamically: we can either add or delete a sub-menu or menu
item at any time; we can also change the text of a menu item, move a sub-menu or menu item, or add a
separator between two menu items. All these things can be implemented at run-time.
Menu Struture
The structure of menu à sub menu à menu item is like a tree. At the topmost level (the root), the
menu comprises several sub-menus. Each sub-menu also comprises several items, which could be a normal
command or another sub-menu. For example, in application Explorer (file browser in Windows95), its
first level menu comprises five sub-menus: File, Edit, View, Tool, and Help. If we examine File submenu,
we will see that it comprises eight items: New, separator, Create Shortcut, Delete, Rename,
Properties, separator and Close. Here, item New is another sub-menu, which comprises several other
menu items. This kind of structure can continue. As long as our program needs, we can organize our menu
into many different levels.
In MFC, class CMenu should be used this way. With a CMenu type pointer to a menu object, we have the
access to only the menu items at certain level. If we want to access a menu item at a lower level, we first
need to access the sub-menu that contains the desired menu item.
This can be explained by the previous “Explorer” example: suppose we have a CMenu type pointer to
the main menu, we can use it to access the first level menu items: File, Edit, View, Tool, and Help. This
means we can use the pointer to disable, enable or set text for any of the above items, but we can not use it
to make change to the items belonging to other levels, for example, New item under File sub-menu. To
access this item, we need to first obtain a CMenu type pointer to File sub-menu, then use it to modify item
File | New.
Inserting and Removing Menu Item
Class CMenu has certain member functions that allow us to insert or delete a menu item dynamically.
We can add either a menu item (including separator), or a whole sub-menu. When we remove a sub-menu,
all the lower level items and sub-menus will be removed.
The function that can be used to insert menu items or sub-menus is CMenu::InsertMenu(…), it has the
following format:
BOOL CMenu::InsertMenu
(
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