Q145857: How to Use Multiple Menus in MFC App That Uses GetDefaultMenu
Article: Q145857
Product(s): Microsoft C Compiler
Version(s): 1.50 1.51 1.52 | 2.00 2.10 2.20
Operating System(s):
Keyword(s): kbcode
Last Modified: 05-FEB-2000
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The information in this article applies to:
- The Microsoft Foundation Classes (MFC), included with:
- Microsoft Visual C++ for Windows, 16-bit edition, versions 1.5, 1.51, 1.52
- Microsoft Visual C++, 32-bit Editions, versions 2.0, 2.1, 2.2, 4.0
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SUMMARY
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In an MFC application, you may occasionally find it useful to switch between
menus within the same frame window, such as when using static splitter windows
or objects in a view requiring a whole new menu. Because the framework provides
automatic support for only one menu per document template (hence per frame),
additional code must be added to switch automatically between multiple menu
resources. MFC provides the undocumented virtual function
CDocument::GetDefaultMenu() to allow the document to determine which menu to
display.
MORE INFORMATION
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When AppWizard generates an SDI or MDI application, it creates a menu resource
by using IDR_MAINFRAME as its resource ID. This menu is displayed at all times
for an SDI application and only when there are no active documents in an MDI
application. For an MDI application, AppWizard also generates a menu resource
for the one multidoc template it creates using IDR_xxxxTYPE as its resource ID.
Additional menu resources can be used by creating them using the resource editor
and associating them with another multidoc template (see CMultiDocTemplate). The
framework will display the menu resource associated with each multidoc template
automatically. This method limits you one menu per document template. To bypass
this limitation, you can override CDocument::GetDefaultMenu() and perform some
calls to display the menu.
MFC uses CMDIChildWnd::m_hMenuShared and CFrameWnd::m_hMenuDefault data members
to determine which menu to display. In an MDI application, the menu resource
associated with each document template is loaded during the construction of the
document templates and copied into CMDIChildWnd::m_hMenuShared. This menu is
then used in CMDIChildWnd::OnUpdateFrameMenu() to set the menu of the MDI Frame
window when there is an active MDI child window.
CMDIChildWnd::OnUpdateFrameMenu() uses CFrameWnd::m_hMenuDefault, which is
loaded during CFrameWnd construction using IDR_MAINFRAME when there are no
active child windows. An SDI program calls CFrameWnd::OnUpdateFrameMenu(), which
uses CFrameWnd::m_hMenuDefault for its menu.
In both an SDI and MDI application, the menu you need to display is obtained from
two other sources before using the m_hMenuShared or m_hMenuDefault menus. The
framework first checks CFrameWnd::m_hMenuAlt. This is used in OLE supported
programs with in-place activated objects that provide its own menus. The second
source it checks is CDocument::GetDefaultMenu(), which is also virtual. The
default implementation of it is to return NULL. This function can be overridden
to allow the program to select the menu to display.
Changing the menus manually is done by calling OnUpdateFrameMenu() and
DrawMenuBar(). You must call CFrameWnd::OnUpdateFrameMenu(NULL) or
CMDIFrameWnd::OnUpdateFrameMenu(NULL) in order to set the new menu into the
window. Call DrawMenuBar() to redraw the menu. Use the following code to
implement for both MDI and SDI:
1. Create a new menu resource (IDR_MYMENU1) in the resource editor.
2. Add an HMENU data member to CMyDocument and override GetDefaultMenu() to
return this data member:
// .h file
// HMENU m_hMyMenu;
// virtual HMENU GetDefaultMenu(); // get menu depending on state
HMENU CMyDocument::GetDefaultMenu()
{
return m_hMyMenu; // just use original default
}
Remember to initialize this member variable to NULL either in the constructor
or CDocument::OnNewDocument().
3. Change and redraw the menu at the desired times. For example, when switching
between splitter panes, this is normally done in CView::OnActivateView(). The
following code shows how to implement it in that function.
// example within CView member function
((CMyDocument*)GetDocument())->m_hMyMenu = ::LoadMenu(
AfxGetResourceHandle(), MAKEINTRESOURCE(IDR_MYMENU1));
((CFrameWnd*)AfxGetMainWnd())->OnUpdateFrameMenu(NULL);
AfxGetMainWnd()->DrawMenuBar();
Be sure to destroy the menu upon exiting the application, and avoid having too
many menus loaded at once.
Menus can also be switched simply by changing the value of
CMDIChildWnd::m_hMenuShared (MDI) or CFrameWnd::m_hMenuDefault (SDI). However,
using GetDefaultMenu() allows a safer method of changing the menus.
For more information about how to share menus between MDI child windows, please
see the following article in the Microsoft Knowledge Base:
Q118435 Sharing Menus Between MDI Child Windows.
REFERENCES
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MFC Source Code.
Additional query words: kbinf 1.00 1.50 1.51 1.52 1.10 2.00 2.10 2.20 2.5 2.50 2.51 2.52 2.52b 3.0 3.00 3.1 3.10 3.2 3.20 4.0 4.00
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Keywords : kbcode
Technology : kbAudDeveloper kbMFC
Version : 1.50 1.51 1.52 | 2.00 2.10 2.20
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