Re: Some queries regarding Menu- dynamic
On 31 Jul 2006 23:23:06 -0700, "Arpit" <arpitpmehta@gmail.com> wrote:
Hi experts,
I m a novice in MFC. i m adding items dynamically in a menu that was
created by default through Application wizard in creating SDI
application . i write the following code in MainFrm.cpp in OnCreate
int CMainFrame::OnCreate(LPCREATESTRUCT lpCreateStruct)
{
//********************************created by
default***************************************************
if (CFrameWnd::OnCreate(lpCreateStruct) == -1)
return -1;
if (!m_wndToolBar.CreateEx(this, TBSTYLE_FLAT, WS_CHILD | WS_VISIBLE |
CBRS_TOP
| CBRS_GRIPPER | CBRS_TOOLTIPS | CBRS_FLYBY | CBRS_SIZE_DYNAMIC) ||
!m_wndToolBar.LoadToolBar(IDR_MAINFRAME))
{
TRACE0("Failed to create toolbar\n");
return -1; // fail to create
}
if (!m_wndStatusBar.Create(this) ||
!m_wndStatusBar.SetIndicators(indicators,
sizeof(indicators)/sizeof(UINT)))
{
TRACE0("Failed to create status bar\n");
return -1; // fail to create
}
// TODO: Delete these three lines if you don't want the toolbar to be
dockable
m_wndToolBar.EnableDocking(CBRS_ALIGN_ANY);
EnableDocking(CBRS_ALIGN_ANY);
DockControlBar(&m_wndToolBar);
//************************************My
code*******************************************************
// Dynamically add menu
pMenuUpdated = this->GetMenu();
pMenuUpdated->AppendMenu(MF_STRING,DRAW_MENU_ID,"Draw");
CMenu* pSubMenuDraw=new CMenu();
ASSERT(pSubMenuDraw->CreateMenu());
That's a bogus ASSERT, and VERIFY wouldn't be much better. CreateMenu is an
operation that can fail, so you must check it for errors. The rather huge
problem with ASSERT is that the asserted code will go away in a release
build, and the menu will not be created. The slightly lesser problem with
VERIFY is that you'll only be notified of errors in a debug build, but
they're equally likely to happen in a release build.
pSubMenuDraw->AppendMenu(MF_STRING,CIRC_MENU_ID,"Circle");
pSubMenuDraw->AppendMenu(MF_STRING,RECT_MENU_ID,"Rectangle");
pSubMenuDraw->AppendMenu(MF_STRING,ERASE_MENU_ID,"Erase All");
pMenuUpdated->ModifyMenu(DRAW_MENU_ID,MF_POPUP,(UINT_PTR)pSubMenuDraw->m_hMenu,"Draw");
// m_hMenuDefault=pMenuUpdated->m_hMenu;
// SetMenu(pMenuUpdated);
// pMenuUpdated->Detach();
// DrawMenuBar();
return 0;
}
My question is very simple.But i dont find the right answer.
1) In
pMenuUpdated->ModifyMenu(DRAW_MENU_ID,MF_POPUP,(UINT_PTR)pSubMenuDraw->m_hMenu,"Draw");
(UINT_PTR)pSubMenuDraw->m_hMenu is for new item.then what exactlly
happens with this handle.Is that get attached to old item i.e.
pMenuUpdated. why do i get submenu on clicking main menu?
Because pMenuUpdated is your main menu, and that hasn't changed.
2) Why i dont need
// m_hMenuDefault=pMenuUpdated->m_hMenu;
// SetMenu(pMenuUpdated);
// pMenuUpdated->Detach();
// DrawMenuBar();
Is it because i dont need to reset the menu handle of windows as i have
used getmenu function
Yes, you're working with your main menu, and because you used GetMenu, you
don't need to call Detach or delete the pointer.
BTW, when you add submenus to another menu like this, the receiving menu
assumes ownership of the HMENU, but the donor menu is none the wiser. So
you should do this afterwards:
pSubMenuDraw->Detach()
--
Doug Harrison
Visual C++ MVP