深入浅出MFC“文档/视图”架构（5）――框架

核心提示： 图5.4 MDI Tile的效果MDISetMenu函数的重要意义体现在一个MDI程序可以为不同类型的文档（与文档模板关联）显示不同的菜单，例如下面的这个函数Load一个菜单，深入浅出MFC“文档/视图”架构（5）――框架(5)，并将目前主窗口的菜单替换为该菜单：void CMdiView

图5.4 MDI Tile的效果

MDISetMenu函数的重要意义体现在一个MDI程序可以为不同类型的文档（与文档模板关联）显示不同的菜单，例如下面的这个函数Load一个菜单，并将目前主窗口的菜单替换为该菜单：

void CMdiView::OnReplaceMenu()
{
　// Load a new menu resource named IDR_SHORT_MENU
　CMdiDoc* pdoc = GetDocument();
　pdoc->m_DefaultMenu = ::LoadMenu(AfxGetResourceHandle(), MAKEINTRESOURCE(IDR_SHORT_MENU));
　if (pdoc->m_DefaultMenu == NULL)
　　return;
　// Get the parent window of this view window. The parent window is
　// a CMDIChildWnd-derived class. We can then obtain the MDI parent
　// frame window using the CMDIChildWnd*. Then, replace the current
　// menu bar with the new loaded menu resource.
　CMDIFrameWnd* frame = ((CMDIChildWnd *) GetParent())->GetMDIFrame();
　frame->MDISetMenu(CMenu::FromHandle(pdoc->m_DefaultMenu), NULL);
　frame->DrawMenuBar();
}　　CMDIFrameWnd类另一个不讲"不足以服众"的函数是OnCreateClient，它是子框架窗口的创造者，其实现如下：

BOOL CMDIFrameWnd::OnCreateClient(LPCREATESTRUCT lpcs, CCreateContext*)
{
　CMenu* pMenu = NULL;
　if (m_hMenuDefault == NULL)
　{
　　// default implementation for MFC V1 backward compatibility
　　pMenu = GetMenu();
　　ASSERT(pMenu != NULL);
　　// This is attempting to guess which sub-menu is the Window menu.
　　// The Windows user interface guidelines say that the right-most
　　// menu on the menu bar should be Help and Window should be one
　　// to the left of that.
　　int iMenu = pMenu->GetMenuItemCount() - 2;
　　// If this assertion fails, your menu bar does not follow the guidelines
　　// so you will have to override this function and call CreateClient
　　// appropriately or use the MFC V2 MDI functionality.
　　ASSERT(iMenu >= 0);
　　pMenu = pMenu->GetSubMenu(iMenu);
　　ASSERT(pMenu != NULL);
　}
　return CreateClient(lpcs, pMenu);
}
　　从CMDIFrameWnd::OnCreateClient的源代码可以看出，其中真正起核心作用的是对函数CreateClient的调用：
BOOL CMDIFrameWnd::CreateClient(LPCREATESTRUCT lpCreateStruct,
CMenu* pWindowMenu)
{
　ASSERT(m_hWnd != NULL);
　ASSERT(m_hWndMDIClient == NULL);
　DWORD dwStyle = WS_VISIBLE | WS_CHILD | WS_BORDER | WS_CLIPCHILDREN | WS_CLIPSIBLINGS |
MDIS_ALLCHILDSTYLES; // allow children to be created invisible
　DWORD dwExStyle = 0;
　// will be inset by the frame
　if (afxData.bWin4)
　{
　　// special styles for 3d effect on Win4
　　dwStyle &= ~WS_BORDER;
　　dwExStyle = WS_EX_CLIENTEDGE;
　}
　CLIENTCREATESTRUCT ccs;
　ccs.hWindowMenu = pWindowMenu->GetSafeHmenu();
　// set hWindowMenu for MFC V1 backward compatibility
　// for MFC V2, window menu will be set in OnMDIActivate
　ccs.idFirstChild = AFX_IDM_FIRST_MDICHILD;
　if (lpCreateStruct->style & (WS_HSCROLL|WS_VSCROLL))
　{
　　// parent MDIFrame's scroll styles move to the MDICLIENT
　　dwStyle |= (lpCreateStruct->style & (WS_HSCROLL|WS_VSCROLL));
　　// fast way to turn off the scrollbar bits (without a resize)
　　ModifyStyle(WS_HSCROLL|WS_VSCROLL, 0, SWP_NOREDRAW|SWP_FRAMECHANGED);
　}
　// Create MDICLIENT control with special IDC
　if ((m_hWndMDIClient = ::CreateWindowEx(dwExStyle, _T("mdiclient"), NULL,
dwStyle, 0, 0, 0, 0, m_hWnd, (HMENU)AFX_IDW_PANE_FIRST,
AfxGetInstanceHandle(), (LPVOID)&ccs)) == NULL)
　{
　　TRACE(_T("Warning: CMDIFrameWnd::OnCreateClient: failed to create MDICLIENT.")
_T(" GetLastError returns 0x%8.8Xn"), ::GetLastError());
　　return FALSE;
　}
　// Move it to the top of z-order
　::BringWindowToTop(m_hWndMDIClient);
　return TRUE;
}