Q242577: PRB: Update Command UI Handlers Do Not Work Properly on Dialogs
Article: Q242577
Product(s): Microsoft C Compiler
Version(s): 6.0
Operating System(s):
Keyword(s): kbDlg kbMenu kbMFC KbUIDesign kbVC600 kbDSupport kbGrpDSMFCATL
Last Modified: 26-JUL-2002
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The information in this article applies to:
- Microsoft Visual C++, 32-bit Enterprise Edition, version 6.0
- Microsoft Visual C++, 32-bit Professional Edition, version 6.0
- Microsoft Visual C++, 32-bit Learning Edition, version 6.0
- The Microsoft Foundation Classes (MFC)
- Microsoft Visual C++.NET (2002)
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SYMPTOMS
========
Changing the state (enable/disable, check/uncheck, change text) of a menu item
from its command user-interface (UI) handler does not work correctly if the menu
is attached to a dialog box:
void CTestDlg::OnUpdateFileExit(CCmdUI* pCmdUI)
{
pCmdUI->Enable(FALSE); //Not calling the command handler, but does not show as disabled.
pCmdUI->SetCheck(TRUE); // Does not show check mark before the text.
pCmdUI->SetRadio(TRUE); // Does not show dot before the text.
pCmdUI->SetText("Close"); //Does not change the text.
}
CAUSE
=====
When a drop-down menu is displayed, the WM_INITMENUPOPUP message is sent prior
to displaying the menu items. The MFC CFrameWnd::OnInitMenuPopup function
iterates through the menu items and calls the update command UI handler for the
item, if there is one. The appearance of each menu item is updated to reflect
its state (enabled/disabled, checked/unchecked).
The update UI mechanism doesn't work for a dialog box-based application because
CDialog has no OnInitMenuPopup handler and it uses CWnd's default handler, which
does not call update command UI handlers for menu items.
RESOLUTION
==========
Use the following steps to resolve this problem:
1. Add an ON_WM_INITMENUPOPUP entry to the message map:
BEGIN_MESSAGE_MAP(CTestDlg, CDialog)
//}}AFX_MSG_MAP
ON_WM_INITMENUPOPUP()
END_MESSAGE_MAP()
2. Add a OnInitMenuPopup member function to your dialog box class and copy the
following code (note that this code is taken largely from
CFrameWnd::OnInitMenuPopup in WinFrm.cpp):
void CTestDlg::OnInitMenuPopup(CMenu *pPopupMenu, UINT nIndex,BOOL bSysMenu)
{
ASSERT(pPopupMenu != NULL);
// Check the enabled state of various menu items.
CCmdUI state;
state.m_pMenu = pPopupMenu;
ASSERT(state.m_pOther == NULL);
ASSERT(state.m_pParentMenu == NULL);
// Determine if menu is popup in top-level menu and set m_pOther to
// it if so (m_pParentMenu == NULL indicates that it is secondary popup).
HMENU hParentMenu;
if (AfxGetThreadState()->m_hTrackingMenu == pPopupMenu->m_hMenu)
state.m_pParentMenu = pPopupMenu; // Parent == child for tracking popup.
else if ((hParentMenu = ::GetMenu(m_hWnd)) != NULL)
{
CWnd* pParent = this;
// Child windows don't have menus--need to go to the top!
if (pParent != NULL &&
(hParentMenu = ::GetMenu(pParent->m_hWnd)) != NULL)
{
int nIndexMax = ::GetMenuItemCount(hParentMenu);
for (int nIndex = 0; nIndex < nIndexMax; nIndex++)
{
if (::GetSubMenu(hParentMenu, nIndex) == pPopupMenu->m_hMenu)
{
// When popup is found, m_pParentMenu is containing menu.
state.m_pParentMenu = CMenu::FromHandle(hParentMenu);
break;
}
}
}
}
state.m_nIndexMax = pPopupMenu->GetMenuItemCount();
for (state.m_nIndex = 0; state.m_nIndex < state.m_nIndexMax;
state.m_nIndex++)
{
state.m_nID = pPopupMenu->GetMenuItemID(state.m_nIndex);
if (state.m_nID == 0)
continue; // Menu separator or invalid cmd - ignore it.
ASSERT(state.m_pOther == NULL);
ASSERT(state.m_pMenu != NULL);
if (state.m_nID == (UINT)-1)
{
// Possibly a popup menu, route to first item of that popup.
state.m_pSubMenu = pPopupMenu->GetSubMenu(state.m_nIndex);
if (state.m_pSubMenu == NULL ||
(state.m_nID = state.m_pSubMenu->GetMenuItemID(0)) == 0 ||
state.m_nID == (UINT)-1)
{
continue; // First item of popup can't be routed to.
}
state.DoUpdate(this, TRUE); // Popups are never auto disabled.
}
else
{
// Normal menu item.
// Auto enable/disable if frame window has m_bAutoMenuEnable
// set and command is _not_ a system command.
state.m_pSubMenu = NULL;
state.DoUpdate(this, FALSE);
}
// Adjust for menu deletions and additions.
UINT nCount = pPopupMenu->GetMenuItemCount();
if (nCount < state.m_nIndexMax)
{
state.m_nIndex -= (state.m_nIndexMax - nCount);
while (state.m_nIndex < nCount &&
pPopupMenu->GetMenuItemID(state.m_nIndex) == state.m_nID)
{
state.m_nIndex++;
}
}
state.m_nIndexMax = nCount;
}
}
STATUS
======
This behavior is by design.
MORE INFORMATION
================
The update command UI handler is also called from CWnd::OnCommand to make sure
that command has not become disabled before routing. This is why the command
handler is not called for a disabled menu item even though it is not grayed
(unavailable). Menu items are not drawn to reflect their status in this case.
This is the related code from the Wincore.cpp file:
// Make sure command has not become disabled before routing.
CTestCmdUI state;
state.m_nID = nID;
OnCmdMsg(nID, CN_UPDATE_COMMAND_UI, &state, NULL);
if (!state.m_bEnabled)
{
TRACE1("Warning: not executing disabled command %d\n", nID);
return TRUE;
}
Steps to Reproduce the Behavior
-------------------------------
Follow these steps to reproduce this behavior in Visual C++ .NET:
1. Create an MFC dialog-based application by using AppWizard.
2. Create a new menu resource and add the File and File/Exit menu items to it.
3. Set this menu as the menu for the dialog box in the dialog box Properties
window. To do this, open the dialog resource in the dialog editor. In the
Properties window, click select Menu. The ID of the new menu resource is
displayed in the Menu property editor drop-down list.
4. Add an UPDATE_COMMAND_UI handler for File/Exit menu item. To do this,
right-clicking File/Exit in the menu editor, and then click Add Event
Handler. In the Event Handler wizard, add the UPDATE_COMMAND_UI handler to
the project CDialog derived class. Click Add and Edit to create the handler,
and then add one of these statements to the generated handler method:
pCmdUI->Enable(FALSE); //Not calling the handler, but does not show as disabled
pCmdUI->SetCheck(TRUE); // Does not show check mark before the text.
pCmdUI->SetRadio(TRUE); // Does not show dot before the text.
pCmdUI->SetText("Close"); //Does not change the text.
5. Build and run the application.
REFERENCES
==========
For additional information, click the article number below to view the article
in the Microsoft Knowledge Base:
Q141751 SAMPLE: Adding Control Bars to Dialog Boxes in MFC
(c) Microsoft Corporation 9/29/1999, All Rights Reserved.
Contributions by Sreedhar Pelluru, Microsoft Corporation
Additional query words: WM_INITMENUPOPUP ON_UPDATE_COMMAND_UI
======================================================================
Keywords : kbDlg kbMenu kbMFC KbUIDesign kbVC600 kbDSupport kbGrpDSMFCATL
Technology : kbVCsearch kbAudDeveloper kbMFC kbVC600 kbVC32bitSearch
Version : :6.0
Issue type : kbprb
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