title: What can cause Windows to send the ID_HELP command twice
body: <p>In my app, I overrode <code>CFrameWnd::OnHelp</code> to open a word doc instead of our old .hlp file.  However, when I press F1, I noticed the function is being executed twice.  I examined the stacks and found that <code>AfxWndProcBase</code> is receiving command <code>0x1E146</code>, and then <code>CWnd::OnCommand</code> is truncating that to <code>0xE146</code> when calling <code>CFrameWnd::OnCmdMsg</code>, and <code>0xE146</code> is the <code>ID_HELP</code> command.  Then immediately after this, <code>AfxWndProcBase</code> is receiving command <code>0xE146</code>, and runs the help command again.  After some experimentation, I've discovered that the second message is being received and processed <em>inside</em> the call to <code>AfxMessageBox</code> when the first message is being processed.</p>
  
  <p>Handler is here:</p>
  
  <pre><code>void CMainFrame::OnHelp() {
    BOOL bWorked;
    STARTUPINFO suInfo = {};
    suInfo.cb = sizeof(suInfo);
    PROCESS_INFORMATION procInfo = {};
    CString m_Process = _T("Start");
    CString vipx = /*_T("\"") +*/ CString(AfxGetApp()-&gt;m_pszHelpFilePath) /*+ _T("\"")*/;
  
    bWorked = ::CreateProcess(m_Process,
               vipx.GetBuffer(),      // requires non-const :(
               NULL,
               NULL,
               FALSE,
               NORMAL_PRIORITY_CLASS,
               NULL,
               NULL,
               &amp;suInfo,
               &amp;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);  
  }
  </code></pre>
  
  <p>Why are both <code>0x1E146</code> and <code>0xE146</code> being sent to my app when I press F1 (and what is the first one?)</p>
  
  <p>After a rewrite, I discovered that calling <code>ShellExecute</code> also causes the "1 deep recursion".</p>
  
  <p>I have no idea if it's relevent, but here's my form's message map:</p>
  
  <pre><code>BEGIN_MESSAGE_MAP(CMainFrame, CFrameWnd)
  //{{AFX_MSG_MAP(CMainFrame)
      ON_WM_CREATE()
  //}}AFX_MSG_MAP
      // Global help commands
      ON_COMMAND(ID_HELP, OnHelp) //F1  &lt;--- both messages are this one?
  END_MESSAGE_MAP()
  </code></pre>
  
  <p>In my resource file I found these, one for F1 and one for Shift+F1:</p>
  
  <pre><code>VK_F1,          ID_CONTEXT_HELP,        VIRTKEY, SHIFT, NOINVERT
  VK_F1,          ID_HELP,                VIRTKEY, NOINVERT
  </code></pre>
  
  <p>Probably useless, but here's the two callstacks:</p>
  
  <pre><code>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++
  </code></pre>
  
  <p>Second message:</p>
  
  <pre><code>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++
  </code></pre>