Re: Critical section-Updating the Dialog from Workerthread
On 29 Mrz., 16:25, scott...@mvps.org wrote:
On Thursday, March 29, 2012 5:26:05 AM UTC-4, Lucress Carol wrote:
Hi every one,
I have a dialog application with a start button, a slider control, an
edit box where the value of the slider control will be displayed and
another edit box where the result of some operations made from a
workerthread will be displayed. When moving the slider, the new value
of the slider should appear in the corresponding edit box and the
workerthread should be aware that the value of the slider has changed
and should update the value of the slider in the calculations being
performed.
I created a class CWorkerThreadMgr (for the thread code) which
contains the followings :
HRESULT Start (HWND hWnd) ; // from where the workert=
hread will
be started
HWND m_hWnd ; //Window handle to the UI di=
alog used to post
messages in order to update
=
//the result of
the calculation in the edit box
HANDLE m_hTread; //handle of the =
worker thread
static UINT WINAPI ThreadProc( LPVOID lptest );
HRESULT Start (HWND hWnd)
{
HRESULT hr=S_OK;
m_hWnd=hWnd;
m_hThread = (HANDLE)_beginthreadex(NULL,0,ThreadProc,
static_cast<LPVOID>(this), 0,NULL);
return hr;
}
// Implementation in the stdafx.h
#define WM_SENDCALCULATED_VALUE WM_APP + 1
// Implementation in the CStartCalculationDlg.h
CWorkerThreadMgr m_WorkerThreadMgr //instance of the
WorkerThreadMgr
CSliderCtrl m_Slider //member variable of the slider control
CString m_SliderValue // member variable of the edit box, where the
current value of the slider control will be
=
//displayed
CString m_Calculation // member variable of the edit box where the
calculated result from the workerthread will
//b=
e displayed via PostMessage
afx_msg LRESULT OnSendCalculatedValue( WPARAM, LPARAM );
afx_msg void OnHScroll(UINT nSBCode, UINT nPos, CScrollBar*
pScrollBar);
// Implementation in CStartCalculationDlg.cpp
BEGIN_MESSAGE_MAP(CStartCalculationDlg, CDialog)
=85
ON_WM_HSCROLL()
ON_MESSAGE(WM_SENDCALCULATED_VALUE, OnSendcalculatedValue)
void CStartCalculationDlg::OnHScroll(UINT nSBCode, UINT nPos,
CScrollBar* pScrollBar)
{
m_SliderValue.Format(_T("%d"),m_Slider.GetPos());
SetDlgItemText(IDC_SLIDER_VALUE,m_SliderValue);
}
BOOL CStartCalculationDlg::OnInitDialog()
{
m_Slider.SetRange(0,50);
m_Slider.SetTicFreq(5);
SetDlgItemText(IDC_SLIDER_VALUE,_T("0"));
}
void CStartCalculationDlg::OnBnClickedStart()
{
m_WorkerThreadMgr.Start(GetSafeHwnd());
}
static UINT WINAPI ThreadProc( LPVOID lptest )
{
CWorkerThreadMgr* pCalculateMgr = reinterpret_cast< CWorkerThreadM=
gr*
( lptest);
//From the thread procedure a random number multiply by the slider
value
//should occur 40 times: rand() *m_SliderValue and the result
displayed in the edit box on the gui
for( UINT uCount = 0; uCount < 40; uCount++ ){
//Check if the slider has been moved
//if so, update the value of the slider for the calculation
...???
//pCalculateMgr-> rand()* m_SliderValue;
PostMessage(pCalculateMgr-> m_hWnd, WM_SENDCALCULATED_VALUE,0,0);
}
}
LRESULT CStartCalculationDlg::OnSendCalculatedValue( WPARAM, LPARAM )
{
// m_SliderValue and m_Slider as critical section ??
m_Calculation.Format(_T("%d"),rand()*m_SliderValue); //???
SetDlgItemText(IDC_CALCULATION, m_Calculation);
return 1;
}
So my questions are the following:
Since I'm not allowed to manipulate the control elements from the
workerthread, how can I implement the =93OnSendCalculatedValue=94
function?
I have to check by each iteration, if the slider value has been
changed, how can I implement it in the Threadproc or should it be
somewhere else?
How can I implement m_Slider and m_SliderValue as critical section? Or
do I need to create new variables in the CWorkerThreadMgr class?
Thank you
Carol
You're trying to multiply a CString (m_SliderValue) by the rand() result.=
Change things so the slider value you work with is an int. Then the thread=
can safely read the int, and it can provide an int result.
When the thread posts the custom message, put the int result into the wPa=
ram or lParam that is part of the message. That way the message handler =
function will receive the new value in the parameter.- Zitierten Text ausbl=
enden -
- Zitierten Text anzeigen -
Thank you for your hint.
When the thread posts the custom message, put the int result into the wPa=
ram or lParam that is part of the message. That way the message handler fun=
ction will receive the new value in the parameter.
I declare in the CWorkerThreadMgr class an integer member variable c
and
I post the message to the gui like this:
PostMessage (pCalculateMgr-> m_hWnd,
WM_SENDCALCULATED_VALUE,pCalculateMgr-> c,0);
and the OnSendCalculatedValue looks like this:
LRESULT CStartCalculationDlg::OnSendCalculatedValue( WPARAM, LPARAM )
{
//m_WorkerThreadMgr: instance of the CWorkerThreadMgr class and
declared as member in the
// in the CStartCalculationDlg class
m_WorkerThreadMgr.c=rand()*m_Slider.GetPos();
m_Calculation.Format(_T("%d"),m_WorkerThreadMgr.c);
SetDlgItemText(IDC_CALCULATION, m_Calculation);
return 1;
}
Is it what you meant or did I get it wrong?
thank you