什么会导致 Windows 发送 ID_HELP 命令两次

Question

在我的应用程序中，我覆盖了 CFrameWnd::OnHelp 以打开 word doc 而不是我们旧的 .hlp 文件。但是，当我按 F1 时，我注意到该函数被执行了两次。我检查了堆栈，发现AfxWndProcBase 正在接收命令0x1E146，然后CWnd::OnCommand 在调用CFrameWnd::OnCmdMsg 时将其截断为0xE146，而0xE146 是ID_HELP 命令。然后紧接着，AfxWndProcBase 正在接收命令0xE146，并再次运行帮助命令。经过一些实验，我发现在处理第一条消息时，在对AfxMessageBox 的调用中接收并处理了第二条消息。

处理程序在这里：

void CMainFrame::OnHelp() {
  BOOL bWorked;
  STARTUPINFO suInfo = {};
  suInfo.cb = sizeof(suInfo);
  PROCESS_INFORMATION procInfo = {};
  CString m_Process = _T("Start");
  CString vipx = /*_T("\"") +*/ CString(AfxGetApp()->m_pszHelpFilePath) /*+ _T("\"")*/;

  bWorked = ::CreateProcess(m_Process,
             vipx.GetBuffer(),      // requires non-const :(
             NULL,
             NULL,
             FALSE,
             NORMAL_PRIORITY_CLASS,
             NULL,
             NULL,
             &suInfo,
             &procInfo);
  vipx.ReleaseBuffer();

  if (procInfo.dwThreadId==NULL || bWorked==false)
      AfxMessageBox(_T("Failed to launch help: " + GetErrNoText(GetLastError())));
  //AfxMessageBox causes my app to receive the message again?

  CloseHandle(procInfo.hProcess);
  CloseHandle(procInfo.hThread);  
}

为什么当我按下 F1 时，0x1E146 和 0xE146 都被发送到我的应用程序（第一个是什么？）

重写后发现调用ShellExecute也会导致“1次深度递归”。

我不知道这是否相关，但这是我的表单的消息映射：

BEGIN_MESSAGE_MAP(CMainFrame, CFrameWnd)
//{{AFX_MSG_MAP(CMainFrame)
    ON_WM_CREATE()
//}}AFX_MSG_MAP
    // Global help commands
    ON_COMMAND(ID_HELP, OnHelp) //F1  <--- both messages are this one?
END_MESSAGE_MAP()

在我的资源文件中，我找到了这些，一个用于 F1，一个用于 Shift+F1：

VK_F1,          ID_CONTEXT_HELP,        VIRTKEY, SHIFT, NOINVERT
VK_F1,          ID_HELP,                VIRTKEY, NOINVERT

可能没用，但这是两个调用堆栈：

MyApp.exe!CMainFrame::OnHelp()  Line 66 C++
mfc90ud.dll!_AfxDispatchCmdMsg(CCmdTarget * pTarget=0x01fea410, unsigned int nID=57670, int nCode=0, void (void)* pfn=0x0040b720, void * pExtra=0x00000000, unsigned int nSig=57, AFX_CMDHANDLERINFO * pHandlerInfo=0x00000000)  Line 82    C++
mfc90ud.dll!CCmdTarget::OnCmdMsg(unsigned int nID=57670, int nCode=0, void * pExtra=0x00000000, AFX_CMDHANDLERINFO * pHandlerInfo=0x00000000)  Line 381 + 0x27 bytes    C++
mfc90ud.dll!CFrameWnd::OnCmdMsg(unsigned int nID=57670, int nCode=0, void * pExtra=0x00000000, AFX_CMDHANDLERINFO * pHandlerInfo=0x00000000)  Line 946 + 0x18 bytes C++
mfc90ud.dll!CWnd::OnCommand(unsigned int wParam=123206, long lParam=0)  Line 2364   C++
mfc90ud.dll!CFrameWnd::OnCommand(unsigned int wParam=123206, long lParam=0)  Line 366   C++
mfc90ud.dll!CWnd::OnWndMsg(unsigned int message=273, unsigned int wParam=123206, long lParam=0, long * pResult=0x0018fba4)  Line 1769 + 0x1e bytes  C++
mfc90ud.dll!CWnd::WindowProc(unsigned int message=273, unsigned int wParam=123206, long lParam=0)  Line 1755 + 0x20 bytes   C++
mfc90ud.dll!AfxCallWndProc(CWnd * pWnd=0x01fea410, HWND__ * hWnd=0x001703da, unsigned int nMsg=273, unsigned int wParam=123206, long lParam=0)  Line 240 + 0x1c bytes   C++
mfc90ud.dll!AfxWndProc(HWND__ * hWnd=0x001703da, unsigned int nMsg=273, unsigned int wParam=123206, long lParam=0)  Line 403    C++
mfc90ud.dll!AfxWndProcBase(HWND__ * hWnd=0x001703da, unsigned int nMsg=273, unsigned int wParam=123206, long lParam=0)  Line 441 + 0x15 bytes   C++
    ...
mfc90ud.dll!CFrameWnd::PreTranslateMessage(tagMSG * pMsg=0x00712740)  Line 249 + 0x1b bytes C++
mfc90ud.dll!CWnd::WalkPreTranslateTree(HWND__ * hWndStop=0x00160bb4, tagMSG * pMsg=0x00712740)  Line 2946 + 0x14 bytes  C++
mfc90ud.dll!AfxInternalPreTranslateMessage(tagMSG * pMsg=0x00712740)  Line 233 + 0x12 bytes C++
mfc90ud.dll!CWinThread::PreTranslateMessage(tagMSG * pMsg=0x00712740)  Line 777 + 0x9 bytes C++
MyApp.exe!CCXMyAppApp::PreTranslateMessage(tagMSG * pMsg=0x00712740)  Line 749  C++
mfc90ud.dll!AfxPreTranslateMessage(tagMSG * pMsg=0x00712740)  Line 252 + 0x11 bytes C++
mfc90ud.dll!AfxInternalPumpMessage()  Line 178 + 0x18 bytes C++

第二条消息：

MyApp.exe!CMainFrame::OnHelp()  Line 66 C++
mfc90ud.dll!_AfxDispatchCmdMsg(CCmdTarget * pTarget=0x01fea410, unsigned int nID=57670, int nCode=0, void (void)* pfn=0x0040b720, void * pExtra=0x00000000, unsigned int nSig=57, AFX_CMDHANDLERINFO * pHandlerInfo=0x00000000)  Line 82    C++
mfc90ud.dll!CCmdTarget::OnCmdMsg(unsigned int nID=57670, int nCode=0, void * pExtra=0x00000000, AFX_CMDHANDLERINFO * pHandlerInfo=0x00000000)  Line 381 + 0x27 bytes    C++
mfc90ud.dll!CFrameWnd::OnCmdMsg(unsigned int nID=57670, int nCode=0, void * pExtra=0x00000000, AFX_CMDHANDLERINFO * pHandlerInfo=0x00000000)  Line 946 + 0x18 bytes C++
mfc90ud.dll!CWnd::OnCommand(unsigned int wParam=57670, long lParam=0)  Line 2364    C++
mfc90ud.dll!CFrameWnd::OnCommand(unsigned int wParam=57670, long lParam=0)  Line 366    C++
mfc90ud.dll!CWnd::OnWndMsg(unsigned int message=273, unsigned int wParam=57670, long lParam=0, long * pResult=0x0018e264)  Line 1769 + 0x1e bytes   C++
mfc90ud.dll!CWnd::WindowProc(unsigned int message=273, unsigned int wParam=57670, long lParam=0)  Line 1755 + 0x20 bytes    C++
mfc90ud.dll!AfxCallWndProc(CWnd * pWnd=0x01fea410, HWND__ * hWnd=0x001703da, unsigned int nMsg=273, unsigned int wParam=57670, long lParam=0)  Line 240 + 0x1c bytes    C++
mfc90ud.dll!AfxWndProc(HWND__ * hWnd=0x001703da, unsigned int nMsg=273, unsigned int wParam=57670, long lParam=0)  Line 403 C++
mfc90ud.dll!AfxWndProcBase(HWND__ * hWnd=0x001703da, unsigned int nMsg=273, unsigned int wParam=57670, long lParam=0)  Line 441 + 0x15 bytes    C++
...
mfc90ud.dll!CWnd::SendMessageW(unsigned int message=273, unsigned int wParam=57670, long lParam=0)  Line 42 + 0x44 bytes    C++
mfc90ud.dll!CWnd::OnHelpInfo(tagHELPINFO * __formal=0x0008c890)  Line 3195  C++
mfc90ud.dll!CWnd::OnWndMsg(unsigned int message=83, unsigned int wParam=0, long lParam=575632, long * pResult=0x0018e5ec)  Line 1948 + 0xd bytes    C++
mfc90ud.dll!CWnd::WindowProc(unsigned int message=83, unsigned int wParam=0, long lParam=575632)  Line 1755 + 0x20 bytes    C++
mfc90ud.dll!AfxCallWndProc(CWnd * pWnd=0x0253a410, HWND__ * hWnd=0x00160bb4, unsigned int nMsg=83, unsigned int wParam=0, long lParam=575632)  Line 240 + 0x1c bytes    C++
mfc90ud.dll!AfxWndProc(HWND__ * hWnd=0x00160bb4, unsigned int nMsg=83, unsigned int wParam=0, long lParam=575632)  Line 403 C++
mfc90ud.dll!AfxWndProcBase(HWND__ * hWnd=0x00160bb4, unsigned int nMsg=83, unsigned int wParam=0, long lParam=575632)  Line 441 + 0x15 bytes    C++
    ...
mfc90ud.dll!CWnd::DefWindowProcW(unsigned int nMsg=83, unsigned int wParam=0, long lParam=575632)  Line 1043 + 0x20 bytes   C++
mfc90ud.dll!CWnd::Default()  Line 274   C++
mfc90ud.dll!CWnd::OnHelpInfo(tagHELPINFO * __formal=0x0008c890)  Line 3198 + 0x8 bytes  C++
mfc90ud.dll!CWnd::OnWndMsg(unsigned int message=83, unsigned int wParam=0, long lParam=575632, long * pResult=0x0018eb70)  Line 1948 + 0xd bytes    C++
mfc90ud.dll!CWnd::WindowProc(unsigned int message=83, unsigned int wParam=0, long lParam=575632)  Line 1755 + 0x20 bytes    C++
mfc90ud.dll!AfxCallWndProc(CWnd * pWnd=0x0253aa28, HWND__ * hWnd=0x000b08c6, unsigned int nMsg=83, unsigned int wParam=0, long lParam=575632)  Line 240 + 0x1c bytes    C++
mfc90ud.dll!AfxWndProc(HWND__ * hWnd=0x000b08c6, unsigned int nMsg=83, unsigned int wParam=0, long lParam=575632)  Line 403 C++
mfc90ud.dll!AfxWndProcBase(HWND__ * hWnd=0x000b08c6, unsigned int nMsg=83, unsigned int wParam=0, long lParam=575632)  Line 441 + 0x15 bytes    C++
    ...
mfc90ud.dll!CWnd::DefWindowProcW(unsigned int nMsg=77, unsigned int wParam=0, long lParam=0)  Line 1043 + 0x20 bytes    C++
mfc90ud.dll!CWnd::WindowProc(unsigned int message=77, unsigned int wParam=0, long lParam=0)  Line 1756 + 0x1c bytes C++
mfc90ud.dll!AfxCallWndProc(CWnd * pWnd=0x0253aa28, HWND__ * hWnd=0x000b08c6, unsigned int nMsg=77, unsigned int wParam=0, long lParam=0)  Line 240 + 0x1c bytes C++
mfc90ud.dll!AfxWndProc(HWND__ * hWnd=0x000b08c6, unsigned int nMsg=77, unsigned int wParam=0, long lParam=0)  Line 403  C++
mfc90ud.dll!AfxWndProcBase(HWND__ * hWnd=0x000b08c6, unsigned int nMsg=77, unsigned int wParam=0, long lParam=0)  Line 441 + 0x15 bytes C++
    ...
mfc90ud.dll!CWnd::WindowProc(unsigned int message=7423648, unsigned int wParam=7423712, long lParam=2016221872)  Line 1755 + 0x20 bytes C++
    ...
mfc90ud.dll!AfxDeactivateActCtx(unsigned long dwFlags=0, unsigned long ulCookie=353633777)  Line 260 + 0x17 bytes   C++
mfc90ud.dll!AFX_MAINTAIN_STATE2::~AFX_MAINTAIN_STATE2()  Line 63 + 0xe bytes    C++

Answer 1

看起来 ID_HELP 是一个预定义的 MFC #define，如果你想继续使用这个 ID，你需要在你的 CWinApp 派生类（参见 this MSDN article）而不是 Frame-class 中有你的处理程序.

或者，您可以将 ID_HELP 替换为您自己的 ID（例如，IDM_HELP），这与预定义的 MFC ID 不冲突，这样您就不会为同一个 ID 获得两个单独的处理程序。

Answer 2

Apperently this person found the same issue谈前因后果。

这种双重事件处理是由于一些遗留代码造成的。

自 Windows 95 起，Windows 自动将 F1 键转换为 WM_HELP 消息（Viorel_ 提到的支持文章）。您注意到 0x4d 消息的处理正是这样做的；这是一些 Windows 代码。然后，当应用程序收到 WM_HELP 消息时，它（可以）通过调用 WinHelp 来处理它。

在 Windows 95 之前，不存在 WM_HELP 消息。处理 F1 的唯一方法是创建一个 VK_F1 快捷方式，并为其添加一个处理程序。 Windows 95 通过添加 WM_HELP 消息，使帮助管理更加容易。从 Win95 开始，您不必再为 ID_HELP 创建 VK_F1 快捷方式。

如果您选择“上下文相关帮助”选项，MFC Appwizard 仍会添加此快捷方式。 MFC 早于 Windows 95！如果您使用上下文相关帮助创建 MFC Appwizard 应用程序，则会为 VK_F1 创建一个快捷方式，与 CFrameWnd::OnHelp() 关联，它将 WM_HELP 消息路由到应用程序的框架窗口。 “到目前为止一切顺利”。

但 Windows 也会自动将 F1 键击转换为 WM_HELP 消息。因此再次调用 CFrameWnd::OnHelp()，因为 WM_HELP 事件由 MFC 处理。

如果您不想被调用两次，请删除资源文件中的键盘快捷键并改为处理 WM_HELP。那么你将有以下过程：

• Windows 捕获 F1 键，生成 WM_HELP

• 代码中 WM_HELP (ON_WM_HELPINFO) 的消息处理程序会捕获 WM_HELP 消息。 MFC 对 WM_HELP 的默认消息处理是发送 WM_COMMAND(ID_HELP) 消息（这是另一个有趣的部分！）

• 代码中 WM_COMMAND(ID_HELP) 的消息处理程序调用默认 MFC 处理。这会运行 winhelp。

以下 CMainFrame 代码不处理两次帮助消息：

ON_WM_HELPINFO()
ON_COMMAND(ID_HELP, &CMDIFrameWndEx::OnHelp)

..


BOOL CMainFrame::OnHelpInfo(HELPINFO* pHelpInfo)
{
    return CMDIFrameWndEx::OnHelpInfo(pHelpInfo);
}

并且不要忘记在资源文件中删除 VK_F1 的快捷方式！

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