【Win32多线程】创建线程、获取线程执行状态、退出线程、错误处理

产生一个线程：

HANDLE CreateThread(
  LPSECURITY_ATTRIBUTES lpThreadAttributes, // SD描述施行与这一新线程的security属性，NULL表示使用缺省值，在windows 95中忽略该参数
  DWORD dwStackSize,                        // initial stack size新线程拥有的堆栈大小，0表示缺省大小,1MB
  LPTHREAD_START_ROUTINE lpStartAddress,    // thread function  函数指针
  LPVOID lpParameter,                       // thread argument  传递到线程函数的参数
  DWORD dwCreationFlags,                    // creation option  允许产生一个暂时挂起的线程，默认为立即运行
  LPDWORD lpThreadId                        // thread identifier  //新的线程ID会被传回到这里
);

第一个使用线程范例：
//多线程出现的执行混乱问题

#define WIN32_LEAN_AND_MEAN
#include
#include
#include


DWORD WINAPI ThreadFunc(LPVOID); //线程标准函数形式
//#define  WINAPI _stdcall


int main()
{
  HANDLE hThrd;
  DWORD threadId;
  int i;
  for(i=0;i<5;i++)
  {
	  hThrd=CreateThread(NULL,0,ThreadFunc,(LPVOID)i,0,&threadId);
     //返回一个核心对象hThrd
	  if(hThrd)
	  {
		  printf("Thread Start %d\n",i);
		  CloseHandle(hThrd);
	  }
  }


  Sleep(2000); //等待这些线程完成,不加这句，主线程将结束，其他线程将无法完成
  return EXIT_SUCCESS;
}


DWORD WINAPI ThreadFunc(LPVOID n)
{
  int i;
  for(i=0;i<10;i++)
  {
	  printf("%d%d%d%d%d%d%d%d\n",n,n,n,n,n,n,n,n);
  }
  return 0;
}

核心对象：CreateThread()返回的handle被称为一个核心对象(kernel object).其和所谓的GDI对象，如画笔、画刷或DC差不多，前者由KERNEL32.DLL管理，后者由GDI32.DLL管理。所谓handle就是一个


指针，指向操作系统内存空间的某样东西，那东西不允许你直接 取得。
Win32核心对象清单：
1.进程(processes)，线程(threads)，文件(files)，事件(events)，信号量(semaphores)，互斥器(mutexes)，管道(Pipes,分为named和anonymous两种）
这些核心对象可以用来整合许多的线程或进程。
GDI对象和核心对象的主要区别：GDI的对象有单一拥护者，不是进程就是线程。核心对象可以有一个以上的拥有者，甚至可以跨进程。

BOOL CloseHandle(
  HANDLE hObject   // handle to object
);

不关闭可能导致资源泄露。不可以依赖“因线程的结束而清理所有被这一线程产生的核心对象”。许多对象，如文件，是被进程所拥有，而非线程拥有，在进程结束之前不能够清理它们。

线程对象与线程的不同：
线程的handle是指向“线程核心对象”，而不是指向线程本身。当调用CloseHandle()并给一个线程handle时候，就是吧引用计数减1.如果该值变为0，对象会自动被操作系统销毁。

判断线程是否结束：

BOOL GetExitCodeThread(
  HANDLE hThread,      // handle to the thread
  LPDWORD lpExitCode   // termination status
);

如果线程结束，结束代码会被放在lpExitCode参数中带回来。如果没有结束，lpExitCode的值是STILL_ACTIVE.
如果成功，返回True,否则返回False;
GetExitCodeThread将传回线程函数ThreadFunc的返回值。
GetExitCodeThread等待一个线程的结束，但这并不是最好的方法


第二个线程范例：
// 示例GetExitCodeThread的用法，获取线程的状态

#define WIN32_LEAN_AND_MEAN
#include
#include
#include
#include
DWORD WINAPI ThreadFunc(LPVOID); //线程标准函数形式


int main()
{
	
  HANDLE hThrd1;
  HANDLE hThrd2;
  DWORD exitCode1=0;
  DWORD exitCode2=0;


  DWORD threadId;


  hThrd1=CreateThread(NULL,0,ThreadFunc,(LPVOID)1,0,&threadId);


  if(hThrd1)
	  printf("Thread 1 launched \n");


  hThrd2=CreateThread(NULL,0,ThreadFunc,(LPVOID)2,0,&threadId);
  if(hThrd2)
	  printf("Thread 2 launched \n");


  for(;;)
  {
	  printf("Press any key to exit..\n");
	  getch();
	  	  //GetExitCodeThread等待一个线程的结束，但这并不是最好的方法
	  GetExitCodeThread(hThrd1,&exitCode1); //GetExitCodeThread将传回线程函数ThreadFunc的返回值
	  GetExitCodeThread(hThrd2,&exitCode2);


	  if(exitCode1==STILL_ACTIVE)
		  puts("Thread 1 is still running ...");
	  if(exitCode2==STILL_ACTIVE)
		  puts("Thread 2 is still running ...");


	  if(exitCode1!=STILL_ACTIVE&&exitCode2!=STILL_ACTIVE)
		  break;




  }
  CloseHandle(hThrd1);
  CloseHandle(hThrd2);
  printf("Thread 1 returned %d\n",exitCode1);
  printf("Thread 2 returned %d\n",exitCode2);


 return  EXIT_SUCCESS;






}
DWORD WINAPI ThreadFunc(LPVOID n)
{
	Sleep((DWORD)n*1000*2);
	return (DWORD)n*2;
}

结束一个线程：

前面是靠线程函数的结束而结束线程。有时候需要更强制性的手法结束一个线程要用ExitThread();

VOID ExitThread(
  DWORD dwExitCode   // exit code for this thread 指示此线程之结束代码
);

它可以在任何时候被调用并且绝对不会返回。任何代码若放在此行之下，保证不会被执行。


如果线程还在运行而我的程序的结束了，会怎么样？？
结束主线程：程序启动后就执行一个线程称为主线程，主线程有两个特点，第一，负责GUI程序中的主消息循环。第二，这一线程的结束（不论是因为返回或因为调用了ExitThread()）会使程序中的所有


线程都被强迫结束，程序也因此结束。其他线程没有机会做清理工作。故在main或WinMain结束之前，总是先等待所有的线程都结束。
建议在主线程中不要调用ExitThread();


第三个线程范例：怎么结束一个线程

#define WIN32_LEAN_AND_MEAN
#include
#include
#include
DWORD WINAPI ThreadFunc(LPVOID); //线程标准函数形式
void AnotherFunc(void);


int main()
{
 HANDLE hThrd;
 DWORD exitCode=0;
 DWORD threadId;
 hThrd=CreateThread(NULL,0,ThreadFunc,(LPVOID)1,0,&threadId);


  if(hThrd)
	  printf("Thread launched.. \n");


  for(;;)
  {
	  bool rc;
	  rc=GetExitCodeThread(hThrd,&exitCode);
	  if(rc&&exitCode!=STILL_ACTIVE)
		  break;
  }


  CloseHandle(hThrd);
  printf("Thread  returned %d\n",exitCode);
   return  EXIT_SUCCESS;




}


DWORD WINAPI ThreadFunc(LPVOID n)
{
  printf("Thread running ..\n");
  AnotherFunc(); //调用一个函数，退出该线程
  return 0;
}


void AnotherFunc()
{
printf("About to exit Thread ..\n");
ExitThread(4);
printf("This will never print ..\n"); //这一行不会被打印
}

/****************错误处理*********************/
可以调用GetLastError获得描述
什么是MTVERIFY？
它是一个宏，这个宏内部记录并解释Win32 GetLastError()的结果。如果Win32函数失败，MTVERIFY()会打印一段简短的文字说明。


如何使用MTVERIFY的范例：
错误处理函数

//示例错误处理
#define WIN32_LEAN_AND_MEAN
#include
#include
#include
//////////////////MTVERIFY宏进入////////////
#include "MtVerify.h"
DWORD WINAPI ThreadFunc(LPVOID);


int main()
{
  HANDLE hThrd;
 DWORD exitCode=0;
 DWORD threadId;
 MTVERIFY(hThrd=CreateThread(NULL,0,ThreadFunc,(LPVOID)1,0,&threadId));


if(hThrd)
	  printf("Thread launched.. \n");


MTVERIFY(CloseHandle(hThrd));


for(;;)
  {
	  bool rc;
	  MTVERIFY(rc=GetExitCodeThread(hThrd,&exitCode));
	  if(rc&&exitCode!=STILL_ACTIVE)
		  break;


  }
printf("Thread  returned %d\n",exitCode);
	return EXIT_SUCCESS;


}


DWORD WINAPI ThreadFunc(LPVOID n)
{
  printf("Thread running ..\n");
  return 0;
}




/**  
* MtVerify.h  
*  
* Error handling for applications in  
* "Multitheading Applications in Win32"  
*  
* The function PrintError() is marked as __inline so that it can be  
* included from one or more C or C++ files without multiple definition  
* errors. For the examples in this book, this works fine.  
* To use the PrintError() in an application, it should be taken out,  
* placed in its own source file, and the "__inline" declaration removed  
* so the function will be globally available.  
*/  
#pragma comment( lib, "USER32" )   
#include    
#include    
#define MTASSERT(a) _ASSERTE(a)   
// 宏定义 __FILE__ 与__LINE__都是预处理符号提供错误信息的描述   
// 如果a返回FALSE就执行PrintError函数   
#define MTVERIFY(a) if (!(a)) PrintError(#a,__FILE__,__LINE__,GetLastError())   
__inline void PrintError(LPSTR linedesc, LPSTR filename, int lineno, DWORD errnum)   
{   
	LPSTR lpBuffer;   
	char errbuf[256];   
#ifdef _WINDOWS   
	char modulename[MAX_PATH];   
#else // _WINDOWS   
	DWORD numread;   
#endif // _WINDOWS   
	// 把从GetLastError()返回的错误码转化为错误信息    
	FormatMessage( FORMAT_MESSAGE_ALLOCATE_BUFFER   
		| FORMAT_MESSAGE_FROM_SYSTEM,   
		NULL,   
		errnum,   
		LANG_NEUTRAL,   
		(LPTSTR)&lpBuffer,   
		0,   
		NULL );   
	wsprintfA(errbuf, "\nThe following call failed at line %d in %s:\n\n"  
		" %s\n\nReason: %s\n", lineno, filename, linedesc, lpBuffer);   
	// 如果是console程序就输出信息到控制台上
#ifndef _WINDOWS   
	WriteFile(GetStdHandle(STD_ERROR_HANDLE), errbuf, strlen(errbuf), &numread, FALSE );   
	// 等待3秒钟是为了使用者看到出错信息   
	Sleep(3000);   
	// 如果是窗口程序就一弹出对话框的形式输出错误信息
#else   
	// 当前exe文件的全路径   
	GetModuleFileName(NULL, modulename, MAX_PATH);   
	// 置弹出窗口在最上层以免被忽略   
	MessageBox(NULL, errbuf, modulename, MB_ICONWARNING|MB_OK|MB_TASKMODAL|MB_SETFOREGROUND);   
#endif   
	// 把结束代码EXIT_FAILURE 交给操作系统
	exit(EXIT_FAILURE);   
}  

多线程综合实例：后台打印，建立一个Win32 Application 

/*多线程后台打印范例*/


/******************************/
/*
 * 
 *
 * Sample code for "Multithreading Applications in Win32"
 * This is from Chapter 2, Listing 2-3
 *
 * Demonstrates background printing
 */

#define WIN32_LEAN_AND_MEAN
#include 
#include 
#include 
#include 
#include 
#include "resource.h"
#include "MtVerify.h"

//
// Macro definitions
//
#define WM_SHOWBITMAP   WM_APP

#define MAX_PRINT_JOBS  64

//
// Structures
//
typedef struct
{   // Information passed to background thread for printing
    HWND hDlg;
    HWND hWndParent;
    HDC hDc;
    BOOL bPrint;    // TRUE if printing;
    char szText[256];
} ThreadPrintInfo;

//
// Global variables
//
HANDLE hInst;
HBITMAP gbmpDisplay;
RECT gDisplayRect;

int gNumPrinting = 0;

// Handle to each created thread
HANDLE gPrintJobs[64]; //保存已经创建的线程

// Height of bitmap returned by DrawText
int iHeight;

// HWND of the dialog so other threads can find it.
HWND hDlgMain;


//
// Function declarations
//
int APIENTRY WinMain(HINSTANCE hInstance/*当前程序运行实例的句柄，每个程序可以运行多个实例*/,
				   HINSTANCE hPrevInstance, /*当前实例前一个实例的句柄 ，win32下为NULL*/
				   LPSTR lpCmdLine, /*指定传递给命令行的参数*/
				   int nCmdShow/*指定程序窗口应该如何显示，如最大化等*/);
LRESULT CALLBACK MainWndProc(HWND hWnd/*标志接受消息的具体窗口*/, unsigned msg, WPARAM wParam, LPARAM lParam);
LRESULT CALLBACK PrintDlgProc(HWND hDlg, UINT uMsg, WPARAM wParam, LPARAM lParam);
BOOL PrintDlg_OnInitDialog(HWND hwndDlg, HWND hwndFocus, LPARAM lParam);
void PrintDlg_OnCommand(HWND hDlg, int id, HWND hwndCtl, UINT codeNotify);
void PrintDlg_OnPaint(HWND hwnd);
void PrintText(HWND hwndParent, char *pszText);
void PrintToDisplay(HWND hwndParent, char *pszText);
LRESULT CALLBACK About(HWND hDlg, UINT message, WPARAM wParam, LPARAM lParam);
DWORD WINAPI BackgroundPrintThread(LPVOID pVoid);


///////////////////////////////////////////////////////////
//
//      WinMain
//
// Main entry point of application. This will be a
// dialog based app, not a normal window, so this
// routine acts a little differently than "normal".
//
int APIENTRY WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow)
{
    MSG     msg;
    HWND    hWnd;
    WNDCLASS wc;
	int index;

    hInst = hInstance;
   //1.设计一个窗口类
    if (!hPrevInstance)
    {
        memset(&wc, 0, sizeof(wc));
        wc.lpfnWndProc  = MainWndProc;
        wc.hInstance    = hInstance;
        wc.hIcon        = LoadIcon (hInstance, "GenIco");
        wc.hCursor      = LoadCursor(NULL,IDC_ARROW);
        wc.hbrBackground= GetSysColorBrush(COLOR_BACKGROUND);
        wc.lpszMenuName = "PRINTING_MENU";
        wc.lpszClassName= "PrintDlgClass";
        if (!RegisterClass(&wc))
            return FALSE;
    }

//2.创建窗口，并返回创建成功后的窗口句柄

    hWnd = CreateWindow(
        "PrintDlgClass",
        "Background Printing",
        WS_OVERLAPPED|WS_CAPTION|WS_MINIMIZEBOX|WS_SYSMENU,
        CW_USEDEFAULT, // At this point we do not want to
        0,             //  show the window until we know
        0,             //  how big the Dialog Box is so
        0,             //  that we can fit the main window
        NULL,          //  around it.
        NULL,
        hInstance,
        NULL);

	    //创建打印对话框
    hDlgMain = CreateDialog(hInst,
                    MAKEINTRESOURCE(IDD_PRINT),
                    hWnd, PrintDlgProc);


	//3.显示及刷新窗口
    ShowWindow(hWnd, nCmdShow);
    ShowWindow(hDlgMain, SW_SHOW);
    //4.消息循环

	while (GetMessage(&msg, NULL, 0, 0))
	{	// Get Next message in queue
		if(hDlgMain == NULL || !IsDialogMessage(hDlgMain,&msg))
		{
			TranslateMessage(&msg); /* Translate virtual key codes */
			DispatchMessage(&msg);	/* Dispatches message to window */
		}
	} // end while

	// Wait for all threads to terminate. The Window will
    // have already disappeared by this point.
	//等待各个线程结束
	for (index = 0; index < gNumPrinting; index++)
	{
		DWORD status;
		do 
		{	// Wait for thread to terminate
			GetExitCodeThread(gPrintJobs[index], &status);
			Sleep(10);
		} while (status == STILL_ACTIVE);

	} // end for

	return (msg.wParam);  /* Returns the value from PostQuitMessage */
}


//主窗口回调函数
LRESULT CALLBACK MainWndProc(HWND hWnd, unsigned msg, WPARAM wParam, LPARAM lParam)
{
    switch (msg)
    {
    case WM_CREATE:
        break;

    case WM_COMMAND:

        switch (wParam)
        {
        case IDM_ABOUT:
            DialogBox(hInst, "AboutBox", hWnd, (DLGPROC)About);
            break;
        case IDM_EXIT:
            PostQuitMessage(0);
            break;
        default:
            return (DefWindowProc(hWnd, msg, wParam, lParam));
        }

    case WM_SETFOCUS:
        // ensure that the Dialog Box has the focus
        SetFocus(hDlgMain);
        break;

    case WM_DESTROY:
        PostQuitMessage(0);
        break;

    default:
        return DefWindowProc(hWnd, msg, wParam, lParam);

    }
    return 0;
}


LRESULT CALLBACK PrintDlgProc(HWND hDlg, UINT uMsg, WPARAM wParam, LPARAM lParam)
{
    switch (uMsg)
    {
    case WM_CLOSE:
        DestroyWindow(hDlg);
        hDlgMain = NULL;
        break;
        
    case WM_DESTROY:
        return TRUE;
        break;

    case WM_SHOWBITMAP:
        if (gbmpDisplay)
            DeleteObject(gbmpDisplay);

        gDisplayRect = *(RECT*)wParam;
        gbmpDisplay = (HBITMAP) lParam;
        InvalidateRect(hDlgMain, NULL, TRUE);
        break;

    HANDLE_MSG(hDlg, WM_INITDIALOG, PrintDlg_OnInitDialog);
    HANDLE_MSG(hDlg, WM_COMMAND, PrintDlg_OnCommand);
    HANDLE_MSG(hDlg, WM_PAINT, PrintDlg_OnPaint);

    default:
        return (FALSE);
    }

    return 0;
}

BOOL PrintDlg_OnInitDialog(HWND hwndDlg, HWND hwndFocus, LPARAM lParam)
{
    RECT rect;

    // Size parent to fit this dialog
    GetWindowRect(hwndDlg, &rect); 
    SetWindowPos(GetParent(hwndDlg),NULL,
        0,0,
        rect.right-rect.left,
        rect.bottom-rect.top+GetSystemMetrics(SM_CYMENU)
            +GetSystemMetrics(SM_CYCAPTION),
        SWP_NOMOVE | SWP_NOZORDER);

    return TRUE;
}

void PrintDlg_OnCommand(HWND hDlg, int id,HWND hwndCtl, UINT codeNotify)
{
    char szText[256];

    switch (id)
    {
    case IDC_PRINT:
        GetDlgItemText(hDlg, IDC_EDIT_TEXT, szText, 256);
        PrintText(hDlg, szText);
        break;

    case IDC_DISPLAY:
        GetDlgItemText(hDlg, IDC_EDIT_TEXT, szText, 256);
        PrintToDisplay(hDlg, szText);
        break;

    case IDCANCEL:
    case IDM_EXIT:
        PostMessage(GetParent(hDlg),WM_DESTROY,
                        (WPARAM)0, (LPARAM)0);
        DestroyWindow(hDlgMain);
        hDlgMain = NULL;
        break;
        
    default:
        break;
    }
}

void PrintDlg_OnPaint( HWND hwnd )
{
    PAINTSTRUCT paint;
    HWND hwndCtrl;
	HDC hdc;
    HDC hDcMem;
    HBITMAP bmpOld;
    RECT rect;
    POINT point;

	if (!gbmpDisplay)
		return;

    hwndCtrl = GetDlgItem(hwnd, IDC_OUTPUT);

    hdc = BeginPaint(hwnd, &paint);

    GetWindowRect(hwndCtrl, &rect);
    point = *((POINT *)&rect);
    ScreenToClient(hwnd, &point);

    hDcMem = CreateCompatibleDC(NULL);
    bmpOld = SelectObject(hDcMem, gbmpDisplay);

    // Copy bitmap to screen
    MTVERIFY( BitBlt(hdc, point.x+10, point.y+40,
        gDisplayRect.right-gDisplayRect.left, gDisplayRect.bottom-gDisplayRect.top,
        hDcMem, iHeight, 0, SRCCOPY) );

    SelectObject(hDcMem, bmpOld);
    DeleteDC(hDcMem);

    EndPaint(hwnd, &paint);
}

//
// Asks user which printer to use, then creates
// background printing thread.
//
void PrintText(HWND hwndParent, char *pszText)
{
    ThreadPrintInfo *pInfo;
    HANDLE hThread;
    DWORD dwThreadId;
    int result;
    DOCINFO docInfo;

    PRINTDLG dlgPrint;

    // Put up Common Dialog for Printing and get hDC.
    memset(&dlgPrint, 0, sizeof(PRINTDLG));
    dlgPrint.lStructSize = sizeof(PRINTDLG);
    dlgPrint.hwndOwner = hwndParent;
    dlgPrint.Flags = PD_ALLPAGES | PD_USEDEVMODECOPIES
           | PD_NOPAGENUMS | PD_NOSELECTION | PD_RETURNDC;
    dlgPrint.hInstance = hInst;
    if (!PrintDlg(&dlgPrint))
        return;

    // Initialize Printer device
    docInfo.cbSize = sizeof(DOCINFO);
    docInfo.lpszDocName = "Background Printing Example";
    docInfo.lpszOutput = NULL;
    docInfo.lpszDatatype = NULL;
    docInfo.fwType = 0;
    result = StartDoc(dlgPrint.hDC, &docInfo);
    result = StartPage(dlgPrint.hDC);

    pInfo = HeapAlloc(GetProcessHeap(),
                      HEAP_ZERO_MEMORY,
                      sizeof(ThreadPrintInfo));
    pInfo->hDlg = hwndParent;
    pInfo->hWndParent = hwndParent;
    pInfo->hDc = dlgPrint.hDC;
    pInfo->bPrint = TRUE;
    strcpy(pInfo->szText, pszText);

    MTVERIFY( hThread = CreateThread(NULL, 0,
        BackgroundPrintThread, (LPVOID)pInfo,
        0, &dwThreadId ));

	// keep track of all background printing threads
    gPrintJobs[gNumPrinting++] = hThread;
}

//
// Shows output on the dialog box.
//
void PrintToDisplay(HWND hwndParent, char *pszText)
{
    ThreadPrintInfo *pInfo;
    DWORD dwThreadId;
    HANDLE hThread;

    pInfo = HeapAlloc(GetProcessHeap(),
                      HEAP_ZERO_MEMORY,
                      sizeof(ThreadPrintInfo));
    pInfo->hDlg = hwndParent;
    pInfo->hWndParent = GetDlgItem(hwndParent, IDC_OUTPUT);
	pInfo->hDc = GetDC(pInfo->hWndParent);
    pInfo->bPrint = FALSE;
    strcpy(pInfo->szText, pszText);

    MTVERIFY( hThread = CreateThread(NULL, 0,
                                     BackgroundPrintThread,
                                     (LPVOID)pInfo,
                                     0, &dwThreadId ));

	// keep track of all background printing threads
    gPrintJobs[gNumPrinting++] = hThread;
}



//---------------------------------------------------------
// About Box Handling
//---------------------------------------------------------

LRESULT CALLBACK About(HWND hDlg, UINT message, WPARAM wParam, LPARAM lParam)
{
    switch (message) {
        case WM_COMMAND:
            if (LOWORD(wParam) == IDOK
                || LOWORD(wParam) == IDCANCEL)
            {
                EndDialog(hDlg, TRUE);
                return (TRUE);
            }
            break;

        default:
            return (DefWindowProc(hDlg, message, wParam, lParam));
    }

    return FALSE;
}


//---------------------------------------------------------
// Background Printing Code后台线程打印函数
//---------------------------------------------------------

DWORD WINAPI BackgroundPrintThread(LPVOID pVoid)
{
    ThreadPrintInfo *pInfo = (ThreadPrintInfo*) pVoid; 
    RECT rect;
    RECT rectMem;
    HDC hDcMem;
    HBITMAP bmpMem;
    HBITMAP bmpOld;
    int x, y;
    int counter = 0;
    int nHeight;
    HFONT hFont;
    HFONT hFontOld;

    // Get dimensions of paper into rect
    rect.left = 0;
    rect.top = 0;
    rect.right =  GetDeviceCaps(pInfo->hDc, HORZRES);
    rect.bottom = GetDeviceCaps(pInfo->hDc, VERTRES);

    nHeight = -MulDiv(36, GetDeviceCaps(pInfo->hDc, LOGPIXELSY), 72);

    // Create Font
    hFont = CreateFont(nHeight, 0, 
        0, 0, FW_DONTCARE, 
        FALSE, FALSE, FALSE, 
        ANSI_CHARSET, 
        OUT_TT_PRECIS, 
        CLIP_DEFAULT_PRECIS,
        PROOF_QUALITY, 
        VARIABLE_PITCH,
        NULL);
    MTASSERT( hFont != 0);

    // Draw into memory device context
    hDcMem = CreateCompatibleDC(pInfo->hDc);
    hFontOld = SelectObject(hDcMem, hFont);
    iHeight = DrawText(hDcMem, pInfo->szText, -1,  &rect, DT_LEFT | DT_NOPREFIX | DT_WORDBREAK | DT_CALCRECT);
    rectMem = rect;
    rectMem.left = rect.left + iHeight;
    rectMem.right = rect.right + (iHeight*2);
    bmpMem = CreateCompatibleBitmap(hDcMem,
                                    rectMem.right, rect.bottom);
    bmpOld = SelectObject(hDcMem, bmpMem);
    OffsetRect(&rect, iHeight, 0); 
    DrawText(hDcMem, pInfo->szText, -1,  &rect,
             DT_LEFT | DT_NOPREFIX | DT_WORDBREAK);

    // Italicize bitmap. We use GetPixel and
    // SetPixel because they are horribly inefficient,
    // thereby causing the thread to run for awhile.
    for (y = 0; y < iHeight; y++)
    {   // Italicize line y
        for (x = rectMem.right; x > iHeight; x--)
        {   // Move specified pixel to the right.
            COLORREF color;
            int offset;
            offset = y - iHeight;
            color = GetPixel(hDcMem, x + offset, y);
            if (color != 0)
                counter++;
            SetPixel(hDcMem, x, y, color);
        } // end for x
    } // end for y
    MTASSERT( counter > 0);

    // Copy bitmap of italicized text from memory to device
    if (pInfo->bPrint)
    {
        BitBlt(pInfo->hDc, 50, 50, rectMem.right-rect.left, rectMem.bottom-rect.top,
            hDcMem, iHeight, 0, SRCCOPY);
    }

    SelectObject(hDcMem, hFontOld);
    SelectObject(hDcMem, bmpOld);
    DeleteDC(hDcMem);

    if (!pInfo->bPrint)
    {
        // We can't just write to the global variable where the
        // bitmap is kept or we might overwrite the work of
        // another thread, thereby "losing" a bitmap

        // Also, if we used PostMessage instead of SendMessage, then
        // the rectangle could have been deleted (it's on the stack)
        // by the time the main message loop is reached.
        SendMessage(pInfo->hDlg, WM_SHOWBITMAP, (WPARAM)&rectMem, (LPARAM) bmpMem);
    }

    if (pInfo->bPrint)
    {   // Finish printing
        int result;

        result = EndPage(pInfo->hDc);
        MTASSERT (result != SP_ERROR);
        result = EndDoc(pInfo->hDc);
        MTASSERT (result != SP_ERROR);
        DeleteDC(pInfo->hDc);
        // If we are printing, we are done with the bitmap.
        DeleteObject(bmpMem);
    } 
    else
    {
        ReleaseDC(pInfo->hWndParent, pInfo->hDc);
    }

    // free data structure passed in.
    HeapFree(GetProcessHeap(), 0, pInfo);

    return 0;
}

多线程应该遵循下面原则：
1.各个线程的数据要分离开来，避免使用全局变量
2.不要在线程之间共享GDI对象
3.让主线程处理GUI界面
4.要等其他线程结束在结束程序

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