Advanced MFC Programming

Chapter 2. Menu
BOOL CMenu::ModifyMenu
(
UINT nPosition, UINT nFlags, UINT nIDNewItem=0, LPCTSTR lpszNewItem = NULL
);
BOOL CMenu::ModifyMenu
(
UINT nPosition, UINT nFlags, UINT nIDNewItem, const CBitmap* pBmp
);
The first version of this function allows us to change a menu item to a text item, a separator, or a submenu.
The second version allows us to change a menu item to a bitmap item. For the second version,
parameter nIDNewItem specifies the new command ID, and parameter pBmp is a pointer to a CBitmap object,
which must contain a valid bitmap resource.
Menu Modification
In the sample application, a bitmap resource ID_BITMAP_QUESTION is prepared for implementing
bitmap menu item. This bitmap contains a question mark. There is no restriction on the bitmap size,
because the size of menu item will be adjusted automatically to let the image fit in.
To load the image, a new CBitmap type variable m_bmpQuestion is declared in class CMainFrame, and
bitmap resource ID_BITMAP_QUESTION is loaded in the constructor of class CMainFrame:
……
……
class CMainFrame : public CFrameWnd
{
protected:
CStatusBar m_wndStatusBar;
CToolBar m_wndToolBar;
CBitmap m_bmpQuestion;
};
CMainFrame::CMainFrame()
{
m_bmpQuestion.LoadBitmap(IDB_BITMAP_QUESTION);
}
The pointer to the system menu is obtained in function CMainFrame::OnCreate(…). First, system
menu’s fifth item (a separator) is modified to a bitmap menu item, then another new command “Resume
standard system menu” is inserted before this bitmap menu item. The IDs of the two commands are
ID_QUESTION and ID_RESUME respectively.
Although we can use any numerical values as the command IDs of the newly added menu items, they
should not be used by other resources of the application. The best way to prevent this from happening is to
generate two new string resources in the application, and use ID_QUESTION and ID_RESUME as their
symbolic IDs. Because Developer Studio will always allocate unused values for new resources, we can
avoid sharing IDs with other resources by using this method.
The following shows how we access the system menu and make changes to its items:
……
int CMainFrame::OnCreate(LPCREATESTRUCT lpCreateStruct)
{
CMenu *ptrMenu;
ptrMenu=GetSystemMenu(FALSE);
ptrMenu->ModifyMenu(5, MF_BYPOSITION, ID_QUESTION, &m_bmpQuestion);
ptrMenu->InsertMenu(5, MF_BYPOSITION, ID_RESUME, "Resume standard system menu");
}
return 0;
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