The Practical Guide to Multithreading - Part 1

// Example2_Dlg.cpp : implementation file
//

#include "stdafx.h"
#include "Example2_Dlg.h"


#define WM_MY_THREAD_MESSAGE	WM_APP+100

// CExample2_Dlg dialog

IMPLEMENT_DYNAMIC(CExample2_Dlg, CDialog)

CExample2_Dlg::CExample2_Dlg(CWnd* pParent /*=NULL*/)
: CDialog(CExample2_Dlg::IDD, pParent),

CancelEvent(FALSE, TRUE)	// Non-signaled, manual-reset
{

}

CExample2_Dlg::~CExample2_Dlg()
{
}

void CExample2_Dlg::DoDataExchange(CDataExchange* pDX)
{
	CDialog::DoDataExchange(pDX);
	DDX_Control(pDX, IDC_START, StartBox);
	DDX_Control(pDX, IDC_END, EndBox);
	DDX_Control(pDX, IDC_PROGRESS, ProgressBar);
	DDX_Control(pDX, IDC_STATUS, StatusText);
}


BEGIN_MESSAGE_MAP(CExample2_Dlg, CDialog)
	ON_BN_CLICKED(ID_CANCEL, &CExample2_Dlg::OnBnClickedCancel)
	ON_BN_CLICKED(IDOK, &CExample2_Dlg::OnBnClickedOk)

	ON_MESSAGE(WM_MY_THREAD_MESSAGE, OnThreadMessage)

END_MESSAGE_MAP()


LRESULT CExample2_Dlg::OnThreadMessage(WPARAM wParam, LPARAM)
{
	int nProgress= (int)wParam;

	// update progress bar
	ProgressBar.SetPos(nProgress);

	CString strStatus;
	strStatus.Format("Processing item: %d", nProgress);

	// update status text
	StatusText.SetWindowText(strStatus);

	return 0;
}

void CExample2_Dlg::OnBnClickedCancel()
{
	GetDlgItem(ID_CANCEL)->EnableWindow(FALSE);

	// Let thread know about this event
	CancelEvent.SetEvent();

	// Wait till target thread responds, and exists
	WaitForSingleObject(ptrThread->m_hThread,INFINITE);

	// update status text
	StatusText.SetWindowText("Canceled!");
}

static UINT Example2Thread(void*);

void CExample2_Dlg::OnBnClickedOk()
{
	// Get start and end values
	StartFrom = GetDlgItemInt(IDC_START);
	EndTo = GetDlgItemInt(IDC_END);

	// Set progress bar range
	ProgressBar.SetRange32(StartFrom, EndTo);

	// Disable button
	GetDlgItem(IDOK)->EnableWindow(FALSE);
	GetDlgItem(ID_CANCEL)->EnableWindow(TRUE);

	// Start off the thread
	ptrThread = AfxBeginThread(Example2Thread, this);
}

UINT Example2Thread(void *pParam)
{
	CExample2_Dlg* pThis= (CExample2_Dlg*)pParam;	

	for (int nValue = pThis->StartFrom; nValue <= pThis->EndTo;  ++nValue)
	{
		if( pThis->CancelEvent.Lock(0) )
			return -1;

		pThis->PostMessage(WM_MY_THREAD_MESSAGE, nValue);	

		Sleep(200);
	}

	return 0;
}