深入探讨MFC消息循环和消息泵

_tWinMain ->AfxWinMain ->AfxWinInit ->CWinThread::InitApplication ->CWinThread::InitInstance ->CWinThread::Run

//thrdcore.cpp
// main running routine until thread exits
int CWinThread::Run()
{
 ASSERT_VALID(this);

 // for tracking the idle time state
 BOOL bIdle = TRUE;
 LONG lIdleCount = 0;

 // acquire and dispatch messages until a WM_QUIT message is received.
 for (;;)
 {
  // phase1: check to see if we can do idle work
  while (bIdle &&
   !::PeekMessage(&m_msgCur, NULL, NULL, NULL, PM_NOREMOVE))
  {
   // call OnIdle while in bIdle state
   if (!OnIdle(lIdleCount++))
    bIdle = FALSE; // assume "no idle" state
  }

  // phase2: pump messages while available
  do
  {
   // pump message, but quit on WM_QUIT
   if (!PumpMessage())
    return ExitInstance();

   // reset "no idle" state after pumping "normal" message
   if (IsIdleMessage(&m_msgCur))
   {
    bIdle = TRUE;
    lIdleCount = 0;
   }

  } while (::PeekMessage(&m_msgCur, NULL, NULL, NULL, PM_NOREMOVE));
 }    //无限循环，退出条件是收到WM_QUIT消息。

 ASSERT(FALSE);  // not reachable
}

if (!PumpMessage())
    return ExitInstance();

//thrdcore.cpp
BOOL CWinThread::PumpMessage()
{
 ASSERT_VALID(this);
 
 //如果是WM_QUIT就退出函数(return FALSE)，这将导致程序结束.
 if (!::GetMessage(&m_msgCur, NULL, NULL, NULL)) {
#ifdef _DEBUG
  if (afxTraceFlags & traceAppMsg)
   TRACE0("CWinThread::PumpMessage - Received WM_QUIT./n");
  m_nDisablePumpCount++; // application must die
   // Note: prevents calling message loop things in 'ExitInstance'
   // will never be decremented
#endif
  return FALSE;
 }

#ifdef _DEBUG
 if (m_nDisablePumpCount != 0)
 {
  TRACE0("Error: CWinThread::PumpMessage called when not permitted./n");
  ASSERT(FALSE);
 }
#endif

#ifdef _DEBUG
 if (afxTraceFlags & traceAppMsg)
  _AfxTraceMsg(_T("PumpMessage"), &m_msgCur);
#endif

 // process this message

 if (m_msgCur.message != WM_KICKIDLE && !PreTranslateMessage(&m_msgCur))

{
  ::TranslateMessage(&m_msgCur); //键转换
  ::DispatchMessage(&m_msgCur); //派送消息
 }
 return TRUE;
}

//thrdcore.cpp
BOOL CWinThread::PreTranslateMessage(MSG* pMsg)
{
 ASSERT_VALID(this);

 // 如果是线程消息，那么将会调用线程消息的处理函数
 if (pMsg->hwnd == NULL && DispatchThreadMessageEx(pMsg))
  return TRUE;

 // walk from target to main window
 CWnd* pMainWnd = AfxGetMainWnd();
 if (CWnd::WalkPreTranslateTree(pMainWnd->GetSafeHwnd(), pMsg))
  return TRUE;

 // in case of modeless dialogs, last chance route through main
 //   window's accelerator table
 if (pMainWnd != NULL)
 {
   CWnd* pWnd = CWnd::FromHandle(pMsg->hwnd);
   if (pWnd->GetTopLevelParent() != pMainWnd)
   return pMainWnd->PreTranslateMessage(pMsg);
 }

 return FALSE;   // no special processing
}

//dlg_5Dlg.cpp
BOOL CDlg_5App::InitInstance()
{
 AfxEnableControlContainer();
#ifdef _AFXDLL
 Enable3dControls();   // Call this when using MFC in a shared DLL
#else
 Enable3dControlsStatic(); // Call this when linking to MFC statically
#endif

 CDlg_5Dlg dlg; //定义一个对话框对象
 m_pMainWnd = &dlg;
 int nResponse = dlg.DoModal(); //对话框的消息循环在这里面开始
 if (nResponse == IDOK)
 {
  // TODO: Place code here to handle when the dialog is
  //  dismissed with OK
 }
 else if (nResponse == IDCANCEL)
 {
  // TODO: Place code here to handle when the dialog is
  //  dismissed with Cancel
 }

 // Since the dialog has been closed, return FALSE so that we exit the
 //  application, rather than start the application's message pump.
 return FALSE;
}

int CWnd::RunModalLoop(DWORD dwFlags)
{
 ASSERT(::IsWindow(m_hWnd)); // window must be created
 ASSERT(!(m_nFlags & WF_MODALLOOP)); // window must not already be in modal state

 // for tracking the idle time state
 BOOL bIdle = TRUE;
 LONG lIdleCount = 0;
 BOOL bShowIdle = (dwFlags & MLF_SHOWONIDLE) && !(GetStyle() & WS_VISIBLE);
 HWND hWndParent = ::GetParent(m_hWnd);
 m_nFlags |= (WF_MODALLOOP|WF_CONTINUEMODAL);
 MSG* pMsg = &AfxGetThread()->m_msgCur;

 // acquire and dispatch messages until the modal state is done
 for (;;)
 {
  ASSERT(ContinueModal());

  // phase1: check to see if we can do idle work
  while (bIdle &&
   !::PeekMessage(pMsg, NULL, NULL, NULL, PM_NOREMOVE))
  {
   ASSERT(ContinueModal());

   // show the dialog when the message queue goes idle
   if (bShowIdle)
   {
    ShowWindow(SW_SHOWNORMAL);
    UpdateWindow();
    bShowIdle = FALSE;
   }

   // call OnIdle while in bIdle state
   if (!(dwFlags & MLF_NOIDLEMSG) && hWndParent != NULL && lIdleCount == 0)
   {
    // send WM_ENTERIDLE to the parent
    ::SendMessage(hWndParent, WM_ENTERIDLE, MSGF_DIALOGBOX, (LPARAM)m_hWnd);
   }
   if ((dwFlags & MLF_NOKICKIDLE) ||
    !SendMessage(WM_KICKIDLE, MSGF_DIALOGBOX, lIdleCount++))
   {
    // stop idle processing next time
    bIdle = FALSE;
   }
  }

  // phase2: pump messages while available
  do
  {
   ASSERT(ContinueModal());

   // pump message, but quit on WM_QUIT
   //PumpMessage(消息泵)的实现和上面讲的差不多。都是派送消息到窗口。
   if (!AfxGetThread()->PumpMessage())
   {
    AfxPostQuitMessage(0);
    return -1;
   }

   // show the window when certain special messages rec'd
   if (bShowIdle &&
    (pMsg->message == 0x118 || pMsg->message == WM_SYSKEYDOWN))
   {
    ShowWindow(SW_SHOWNORMAL);

    UpdateWindow();
    bShowIdle = FALSE;
   }

   if (!ContinueModal())
    goto ExitModal;

   // reset "no idle" state after pumping "normal" message
   if (AfxGetThread()->IsIdleMessage(pMsg))
   {
    bIdle = TRUE;
    lIdleCount = 0;
   }

  } while (::PeekMessage(pMsg, NULL, NULL, NULL, PM_NOREMOVE));
 } //无限循环

ExitModal:
 m_nFlags &= ~(WF_MODALLOOP|WF_CONTINUEMODAL);
 return m_nModalResult;
}

if (!ContinueModal())
 goto ExitModal;
  决定是否退出循环，消息循环函数返回也就是快要结束结束程序了。
BOOL CWnd::ContinueModal()
{
 return m_nFlags & WF_CONTINUEMODAL;
}

//wincore.cpp
void CWnd::EndModalLoop(int nResult)
{
 ASSERT(::IsWindow(m_hWnd));

 // this result will be returned from CWnd::RunModalLoop
 m_nModalResult = nResult;

 // make sure a message goes through to exit the modal loop
 if (m_nFlags & WF_CONTINUEMODAL)
 {
  m_nFlags &= ~WF_CONTINUEMODAL;
  PostMessage(WM_NULL);
 }
}

LRESULT CDlg_5Dlg::OnKickIdle(WPARAM w,LPARAM l)
 {
      //调用CWnd::UpdateDialogControls更新用户界面
     UpdateDialogControls(this, TRUE);
     return 0;
 }

 CMyDlg* pdlg = new CMyDlg;
 pdlg ->Create(IDD_DIALOG1);
 pdlg->ShowWindow(SW_SHOW);
 MessageBox("abc");

while(1)
{
    PostQuitMessage(0); //程序照样down.
}

void CTest_recalclayoutView::OnTimer(UINT nIDEvent)
{
 // TODO: Add your message handler code here and/or call default
 MessageBox("abc");
 while(1); //设计一个死循环
 CView::OnTimer(nIDEvent);
}

BOOL CChildView::PeekAndPump()
{
 MSG msg;
 while(::PeekMessage(&msg,NULL,0,0,PM_NOREMOVE))
 {
  if(!AfxGetApp()->PumpMessage())
  {
   ::PostQuitMessage(0);
   return false;
  }
 }
 return true;
}