如果不是，从消息队列中取出消息，进行处理，直到消息队列为空。
/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));
} 
ASSERT(FALSE); // not reachable
}

BOOL CWinThread::PumpMessage()

{

ASSERT_VALID(this);

if (!::GetMessage(&m_msgCur, NULL, NULL, NULL))

return FALSE;

// process this message

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

{

::TranslateMessage(&m_msgCur);

::DispatchMessage(&m_msgCur);

}

return TRUE;

}