【转】Windows消息投递流程：WM_COMMAND消息流程

原文网址：http://blog.csdn.net/hyhnoproblem/article/details/6182585

该示例通过研究基本的单文档程序的“文件”－－“打开”命令，分析WM_COMMAND消息投递流程。基于VS 2005 代码

 

AfxWndProc最终调用的是OnWndMsg，这个函数负责消息的分发处理。当消息是WM_COMMAND时，将消息投递给OnCommand函数。

 

// wincore.cpp 1746
BOOL CWnd::OnWndMsg(UINT message, WPARAM wParam, LPARAM lParam, LRESULT* pResult)
{
    LRESULT lResult = 0;
    union MessageMapFunctions mmf;
    mmf.pfn = 0;
    CInternalGlobalLock winMsgLock;
    // special case for commands
    if (message == WM_COMMAND)
    {
        if (OnCommand(wParam, lParam))
        {
            lResult = 1;
            goto LReturnTrue;
        }
        return FALSE;
    }
    //...
}

 

 

 

OnCommand是个虚函数，因为消息是主窗口产生的，所以调用的是CFrameWnd::OnCommand函数该函数先检查该消息是不是在线请求帮助，如果是，则程序给框架窗口发送一个WM_COMMANDHELP消息，否则交由基类CWnd::OnCommand()处理。

 

// winfrm.cpp 299
BOOL CFrameWnd::OnCommand(WPARAM wParam, LPARAM lParam)
// return TRUE if command invocation was attempted
{
    HWND hWndCtrl = (HWND)lParam;
    UINT nID = LOWORD(wParam);
    CFrameWnd* pFrameWnd = GetTopLevelFrame();
    ENSURE_VALID(pFrameWnd);
    if (pFrameWnd->m_bHelpMode && hWndCtrl == NULL &&
        nID != ID_HELP && nID != ID_DEFAULT_HELP && nID != ID_CONTEXT_HELP)
    {
        // route as help
        if (!SendMessage(WM_COMMANDHELP, 0, HID_BASE_COMMAND+nID))
            SendMessage(WM_COMMAND, ID_DEFAULT_HELP);
        return TRUE;
    }
    // route as normal command
    return CWnd::OnCommand(wParam, lParam);
}

 

 

 

CWnd::OnCommand首先检查表示控件的LPARAM。如果消息是由控件产生的，LPARAM就会包含控件窗口句柄。如果消息是控件通知，框架就会执行特定的处理过程。如果消息是为某个控件产生的，OnCommand会将消息直接发送给控件，然后OnCommand返回。否则，CWnd::OnCommand()要确保产生命令的界面元素没有被禁用，然后将消息传递给OnCmdMsg函数，调用的是CFrameWnd::OnCmdMsg函数

 

// wParam
//  The high-order word specifies the notification code if the message is from a control.
//  If the message is from an accelerator, this value is 1. If the message is from a menu,
//  this value is zero.
//  The low-order word specifies the identifier of the menu item, control, or accelerator.
// lParam
//  Handle to the control sending the message if the message is from a control.
//  Otherwise, this parameter is NULL.
BOOL CWnd::OnCommand(WPARAM wParam, LPARAM lParam)
// return TRUE if command invocation was attempted
{
    UINT nID = LOWORD(wParam);
    HWND hWndCtrl = (HWND)lParam;
    int nCode = HIWORD(wParam);
    // default routing for command messages (through closure table)
    if (hWndCtrl == NULL)
    {   // 菜单命令先走这里
        // zero IDs for normal commands are not allowed
        if (nID == 0)
            return FALSE;
        // make sure command has not become disabled before routing
        CTestCmdUI state;
        state.m_nID = nID;
        OnCmdMsg(nID, CN_UPDATE_COMMAND_UI, &state, NULL);      // CFrameWnd::OnCmdMsg
        if (!state.m_bEnabled)
        {
            TRACE(traceAppMsg, 0, "Warning: not executing disabled command %d/n", nID);
            return TRUE;
        }
        // menu or accelerator
        nCode = CN_COMMAND;
    }
    else
    {
        // ToolBar命令走这里，或控件通知
        // control notification
        ASSERT(nID == 0 || ::IsWindow(hWndCtrl));
        if (_afxThreadState->m_hLockoutNotifyWindow == m_hWnd)
            return TRUE;        // locked out - ignore control notification
        // reflect notification to child window control
        if (ReflectLastMsg(hWndCtrl))
            return TRUE;    // eaten by child
        // zero IDs for normal commands are not allowed
        if (nID == 0)
            return FALSE;
    }
    // 调用CFrameWnd::OnCmdMsg
    return OnCmdMsg(nID, nCode, NULL, NULL);
}

 

 

 

CFrameWnd::OnCmdMsg函数调用时，pExtra和pHandlerInfo是NULL，因为处理命令不需要这一信息。取出的消息按照以下顺序经过应用程序的各个部分：活动视图、活动视图的文档、文档模板、主窗口、应用程序。

 

// winfrm.cpp 880
BOOL CFrameWnd::OnCmdMsg(UINT nID, int nCode, void* pExtra,
                         AFX_CMDHANDLERINFO* pHandlerInfo)
{
    CPushRoutingFrame push(this);
    // 将消息传递给活动视图，调用CView::OnCmdMsg
    CView* pView = GetActiveView();
    if (pView != NULL && pView->OnCmdMsg(nID, nCode, pExtra, pHandlerInfo))
        return TRUE;
    // 由框架处理该消息，CWnd没有覆盖OnCmdMsg，调用CCmdTarget::OnCmdMsg
    if (CWnd::OnCmdMsg(nID, nCode, pExtra, pHandlerInfo))
        return TRUE;
    // 将消息传递给应用程序，CWinApp没有覆盖OnCmdMsg，所以调用CCmdTarget::OnCmdTarget
    CWinApp* pApp = AfxGetApp();
    if (pApp != NULL && pApp->OnCmdMsg(nID, nCode, pExtra, pHandlerInfo))
        return TRUE;
    return FALSE;
}
// viewcore.cpp 154
BOOL CView::OnCmdMsg(UINT nID, int nCode, void* pExtra,
                     AFX_CMDHANDLERINFO* pHandlerInfo)
{
    // 首先由活动视图处理该消息，调用CCmdTarget::OnCmdMsg
    if (CWnd::OnCmdMsg(nID, nCode, pExtra, pHandlerInfo))
        return TRUE;
    // then pump through document
    if (m_pDocument != NULL)
    {
        // 将该消息传递给视图对应的文档，调用CDocument::OnCmdMsg
        CPushRoutingView push(this);
        return m_pDocument->OnCmdMsg(nID, nCode, pExtra, pHandlerInfo);
    }
    return FALSE;
}
// doccore.cpp 834
BOOL CDocument::OnCmdMsg(UINT nID, int nCode, void* pExtra,
                         AFX_CMDHANDLERINFO* pHandlerInfo)
{
    if (CCmdTarget::OnCmdMsg(nID, nCode, pExtra, pHandlerInfo))
        return TRUE;
    // otherwise check template，调用CDocTemplate::OnCmdMsg
    if (m_pDocTemplate != NULL &&
        m_pDocTemplate->OnCmdMsg(nID, nCode, pExtra, pHandlerInfo))
        return TRUE;
    return FALSE;
}
// doctempl.cpp 370
BOOL CDocTemplate::OnCmdMsg(UINT nID, int nCode, void* pExtra,
                            AFX_CMDHANDLERINFO* pHandlerInfo)
{
    BOOL bReturn;
    CCmdTarget* pFactory = DYNAMIC_DOWNCAST(CCmdTarget, m_pAttachedFactory);
    if (nCode == CN_OLE_UNREGISTER && pFactory != NULL)
        bReturn = pFactory->OnCmdMsg(nID, nCode, pExtra, pHandlerInfo);
    else
        bReturn = CCmdTarget::OnCmdMsg(nID, nCode, pExtra, pHandlerInfo);
    return bReturn;
}

 

 

 

上面的一些函数确定了程序执行流程，最终会调用到CCmdTarget::OnCmdMsg，该函数通过查找消息映射表，进而调用到消息处理函数。

 

// cmdtarg.cpp 297
BOOL CCmdTarget::OnCmdMsg(UINT nID, int nCode, void* pExtra,
                          AFX_CMDHANDLERINFO* pHandlerInfo)
{
    // ...
    // determine the message number and code (packed into nCode)
    const AFX_MSGMAP* pMessageMap;
    const AFX_MSGMAP_ENTRY* lpEntry;
    UINT nMsg = 0;
    //...
    if (nCode != CN_UPDATE_COMMAND_UI)
    {
        nMsg = HIWORD(nCode);
        nCode = LOWORD(nCode);
    }
    //...
    // for backward compatibility HIWORD(nCode)==0 is WM_COMMAND
    if (nMsg == 0)
        nMsg = WM_COMMAND;
    // look through message map to see if it applies to us
    for (pMessageMap = GetMessageMap(); pMessageMap->pfnGetBaseMap != NULL;
        pMessageMap = (*pMessageMap->pfnGetBaseMap)())
    {
        // Note: catches BEGIN_MESSAGE_MAP(CMyClass, CMyClass)!
        ASSERT(pMessageMap != (*pMessageMap->pfnGetBaseMap)());
        lpEntry = AfxFindMessageEntry(pMessageMap->lpEntries, nMsg, nCode, nID);
        if (lpEntry != NULL)
        {
            // found it
            return _AfxDispatchCmdMsg(this, nID, nCode,
                lpEntry->pfn, pExtra, lpEntry->nSig, pHandlerInfo);
        }
    }
    return FALSE;   // not handled
}