UI-thread with both message pump and an infinite loop

GameProfessor

hi, I need to create an UI-thread. The main task of this thread is to perform an infinite loop that do the sending/receiving data. This thread must be able to receive message from Main thread to change behaviour. I try to put the loop in CMyThread::Run() and put the PeekMessage also in the loop but it doesn't work. I don't know how to do it. int CMyThread::Run() { for (;;) { DoMyWork(); if (PeekMessage(&msg, NULL, 0, 0, PM_NOREMOVE )!=0) // my UI thread has no window { TranslateMessage(&msg); DispatchMessage(&msg); } } return CWinThread::Run(); }

Stephen Hewitt

GameProfessor wrote:

I need to create an UI-thread. The main task of this thread is to perform an infinite loop that do the sending/receiving data.

If the thread spends its time in an "infinite loop that do the sending/receiving data" it sounds like you're after a worker thread and not a UI thread; in which case a message pump may not be needed.

Steve

Stephen Hewitt

GameProfessor wrote:

if (PeekMessage(&msg, NULL, 0, 0, PM_NOREMOVE )!=0) // my UI thread has no window { TranslateMessage(&msg); DispatchMessage(&msg); }

This code should look like this:

while ( PeekMessage(&msg, NULL, 0, 0, PM_REMOVE) )
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}

Your code continually dispatches the same message forever since you're using the PM_NOREMOVE flag. I also use while instead of if: do some work, process all outstanding messages then repeat.

Steve

GameProfessor

It doesn't work. I defined my message handler using ON_THREAD_MESSAG macro. And it seems that I must left the CMyThread::Run intact then these message handler can work. How can I have my thread keep on running my send/recv loop while still be able to handle message from the main thread ?

kasturi_haribabu

I think that you also introduce atleast a Sleep(0) after the DispatchMessage statement.

Stephen Hewitt

That's because by implementing your own message pump instead of using CWinThread’s you’re bypassing MFC’s message routing architecture. There are always such dangers when mixing low-level code (Win32 calls) and high-level code (MFC’s CWinThread) without understanding how they relate to each other. To do what you’re trying to do within the MFC architecture proceed as follows: 1. Override your CMyThread's OnIdle member function. It should look like this:

BOOL CMyThread::OnIdle(LONG lCount)
{
DoMyWork();
CWinThread::OnIdle(lCount);
return TRUE;
}

2. Remove your CMyThread::Run override.

Steve

GameProfessor

It still doesn't work. Actually, can DispatchMessage() work with a message handler defined using macro ON_THREAD_MESSAGE ?

Stephen Hewitt

What for? It will not help.

Steve

Stephen Hewitt

I don't think so.

Steve

GameProfessor

this doesn't work because things in OnIdle() can not be a loop and the framework doesn't loop that function by itself. I need an infinite loop. I have try these two methods: Method 1: --> my thread can not handle any message from main thread BOOL CMyThread::OnIdle(LONG lCount) { for(;;) { DoMyWork(); } CWinThread::OnIdle(lCount); return TRUE; } Method 2: --> DoMyWork() only run one time after we send message from Main thread to My thread. BOOL CMyThread::OnIdle(LONG lCount) { DoMyWork(); CWinThread::OnIdle(lCount); return TRUE; } I expect DoMyWork() to be loop to run forever !!! There must be a way, isn't it?

Stephen Hewitt

GameProfessor wrote:

this doesn't work because things in OnIdle() can not be a loop

It will work: the loop is within MFC's CWinThread::Run function. There should be ***NO*** loop inside OnIdle! Try it and see. Remember to remove your Run override.

Steve

GameProfessor

i'm sure it wont run because it's the first thing I've tried. !!! Here's the code: LRESULT CMyThread::OnMyMsg(WPARAM wParam, LPARAM lParam) { MessageBox(NULL,"super man","MyMSG message",MB_OK); // this never show up!!! return 0; } int CMyThread::Run() { for (;;) { i++; if (i>=10000) { i = 0; } } return CWinThread::Run(); } BOOL CMyThread::OnIdle(LONG lCount) { // TODO: Add your specialized code here and/or call the base class return CWinThread::OnIdle(lCount); }

Stephen Hewitt

I know it will; I've just build a test app from scratch and it does. So just try it ok! Here's code snippits: --------------------- // From CMyThead's implementation: BEGIN_MESSAGE_MAP(CMyThread, CWinThread) //{{AFX_MSG_MAP(CMyThread) // NOTE - the ClassWizard will add and remove mapping macros here. //}}AFX_MSG_MAP ON_THREAD_MESSAGE(WM_USER, OnFromUI) // *******IMPORTANT******* END_MESSAGE_MAP() ///////////////////////////////////////////////////////////////////////////// // CMyThread message handlers BOOL CMyThread::OnIdle(LONG lCount) { DoMyWork(); // *******IMPORTANT******* CWinThread::OnIdle(lCount); // *******IMPORTANT******* return TRUE; // *******IMPORTANT******* } void CMyThread::DoMyWork() { } afx_msg LRESULT CMyThread::OnFromUI(WPARAM, LPARAM) { return 0; } // Creating the thead and a dialog: BOOL CWillWorkApp::InitInstance() { // Standard initialization // If you are not using these features and wish to reduce the size // of your final executable, you should remove from the following // the specific initialization routines you do not need. #ifdef _AFXDLL Enable3dControls(); // Call this when using MFC in a shared DLL #else Enable3dControlsStatic(); // Call this when linking to MFC statically #endif CWinThread *pThread = AfxBeginThread(RUNTIME_CLASS(CMyThread)); CWillWorkDlg dlg(pThread); m_pMainWnd = &dlg; int nResponse = dlg.DoModal(); 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; } // In the dialog: CWillWorkDlg::CWillWorkDlg(CWinThread *pThread, CWnd* pParent /*=NULL*/) : CDialog(CWillWorkDlg::IDD, pParent) , m_pThread(pThread) // *******IMPORTANT******* { //{{AFX_DATA_INIT(CWillWorkDlg) // NOTE: the ClassWizard will add member initialization here //}}AFX_DATA_INIT // Note that LoadIcon does not require a subsequent DestroyIcon in Win32 m_hIcon = AfxGetApp()->LoadIcon(IDR_MAINFRAME); } void CWillWorkDlg::OnButton1() { m_pThread->PostThreadMessage(WM_USER, 0, 0); // *******IMPORTANT******* } =========================== CMyThread::DoMyWork() is called continuously and CMyThread::OnFromUI is called when I press a button from a dia

Stephen Hewitt

The reason your code doesn't work is that you haven't removed your Run override as I instructed. MFC's message pump is in CWinThread::Run but your override (CMyThread::Run) never calls it because it enters an endless loop and the call to MFC's is after it. Remove your Run function entirely.

Steve