RunModalLoop

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于 2018-11-04 13:37:46 发布

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本文详细解析了Windows应用程序中模态循环的实现机制，包括如何处理消息队列、如何进行空闲工作检查以及如何在不同的消息阶段进行窗口显示和更新。通过深入理解intCWnd::RunModalLoop函数，读者可以更好地掌握Windows应用程序的模态对话框处理流程。

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 = AfxGetCurrentMessage();

   // 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
           if (!AfxPumpMessage())
           {
               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 (AfxIsIdleMessage(pMsg))
           {
               bIdle = TRUE;
               lIdleCount = 0;
           }

} while (::PeekMessage(pMsg, NULL, NULL, NULL, PM_NOREMOVE));
}

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