Sharing Menus Between MDI Child Windows
ID: Q118435
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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 1.0, 1.5
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Microsoft Visual C++, 32-bit Editions, versions 1.0, 2.0, 4.0
SUMMARY
The document-template model used in the MFC assumes that each template will
have its own set of distinct resources that are all identified by the same
resource ID. However, when dealing with similar MDI child windows, you may
want to conserve resource space and have MDI child windows share the same
menu resource.
MORE INFORMATION
Each CMultiDocTemplate object has a member variable, "m_hMenuShared", that
stores the handle of the menu to be used for that child window. However,
because the default CMultiDocTemplate object assumes that it is the only
user of this member variable, a new class (for example, CSharedDocTemplate)
must be derived to avoid having the CMultiDocTemplate destructor call
DestroyMenu on the shared menu handle:
class CSharedDocTemplate : public CMultiDocTemplate
{
public:
CSharedDocTemplate(UINT nIDResource, CRuntimeClass* pDocClass,
CRuntimeClass* pFrameClass, CRuntimeClass* pViewClass);
virtual ~CSharedDocTemplate();
};
CSharedDocTemplate::CSharedDocTemplate(UINT nIDResource,
CRuntimeClass* pDocClass, CRuntimeClass* pFrameClass,
CRuntimeClass* pViewClass) : CMultiDocTemplate(nIDResource, pDocClass,
pFrameClass, pViewClass)
{
}
CSharedDocTemplate::~CSharedDocTemplate()
{
// This prevents the base class virtual destructor from
// destroying the menu resource (i.e. its checks to make
// sure the handle isn't NULL)
m_hMenuShared = NULL;
}
At this point, declare a public member variable to hold the common menu for
the application; the CWinApp-derived object will take the responsibility of
loading and destroying the common menu.
class CMyApp : public CWinApp
{
public:
HMENU m_ghMenuShared;
//...
};
Now, after the CSharedDocTemplate object has been created, you need to set
its public member variable to the common menu resouce for the application.
The following code fragments demonstrate how to set the handle for a single
template or traverse the template list and set the common handle for all
CSharedDocTemplate objects. Either of these code fragments could be used in
the InitInstance of the CWinApp-derived object:
BOOL CMyApp::InitInstance()
{
...
// New member of CWinApp derived class to store menu handle
m_ghMenuShared = ::LoadMenu(m_hInstance,
MAKEINTRESOURCE(IDR_SHAREDMENU));
CSharedDocTemplate* pDocTemplate;
pDocTemplate = new CSharedDocTemplate(
IDR_MYTYPE, // No menu resource should exist for
// this ID, the menu is set manually
RUNTIME_CLASS(CMDIMyDoc),
RUNTIME_CLASS(CMDIChildWnd),
RUNTIME_CLASS(CMDIMyView));
pDocTemplate->m_hMenuShared = m_ghMenuShared;
AddDocTemplate(pDocTemplate);
...
}
-or-
BOOL CMyApp::InitInstance()
{
...
m_ghMenuShared = ::LoadMenu(m_hInstance,
MAKEINTRESOURCE(IDR_SHAREDMENU));
if (!m_templateList.IsEmpty())
{
CDocTemplate *pDocTemplate;
for (POSITION rPos = m_templateList.GetHeadPosition();
rPos != NULL;)
{
pDocTemplate = m_templateList.GetNext(rPos);
if (pDocTemplate->IsKindOf(RUNTIME_CLASS(CSharedDocTemplate)))
((CSharedDocTemplate *)pDocTemplate)->m_hMenuShared =
m_ghMenuShared;
}
}
...
}
Lastly, you need to destroy the menu resource loaded in InitInstance. This
can easily be accomplished by overriding the ExitInstance member of the
CWinApp-derived class:
int CMyApp::ExitInstance()
{
::DestroyMenu(m_ghMenuShared);
}
Additional query words:
kbinf 1.00 1.50 2.00 2.10 2.50 3.00 4.00
Keywords : kbnokeyword kbMFC kbVC
Version : 1.00 1.50 | 1.00 2.00 4.00
Platform : NT WINDOWS
Issue type :