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http://blog.csdn.net/lights_joy/

lights@hb165.com

 

本文適用于

SDL-1.2.13

vs2008

Windows XP

 

歡迎轉載，但請保留作者信息

SDL的設計并沒有考慮到要和MFC相結合，但是既然它要在windows的系統上運行，必然需要使用Windows提供的API。為了在MFC SDI中使用SDL，首先想到的就是替換SDL創建的窗口，改為使用MFC提供的窗口。

想想在Windows下要創建窗口需要使用的API必然是CreateWindow，在SDL代碼中搜，很容易發現了這樣一段代碼：

int DIB_CreateWindow(_THIS)

{

     char *windowid = SDL_getenv("SDL_WINDOWID");

 

     SDL_RegisterApp(NULL, 0, 0);

 

     SDL_windowid = (windowid != NULL);

     if ( SDL_windowid ) {

#if defined(_WIN32_WCE) && (_WIN32_WCE < 300)

         /* wince 2.1 does not have strtol */

         wchar_t *windowid_t = SDL_malloc((SDL_strlen(windowid) + 1) * sizeof(wchar_t));

         MultiByteToWideChar(CP_ACP, MB_PRECOMPOSED, windowid, -1, windowid_t, SDL_strlen(windowid) + 1);

         SDL_Window = (HWND)wcstol(windowid_t, NULL, 0);

         SDL_free(windowid_t);

#else

         SDL_Window = (HWND)SDL_strtoull(windowid, NULL, 0);

#endif

         if ( SDL_Window == NULL ) {

              SDL_SetError("Couldn't get user specified window");

              return(-1);

         }

 

         /* DJM: we want all event's for the user specified

              window to be handled by SDL.

          */

         userWindowProc = (WNDPROCTYPE)GetWindowLongPtr(SDL_Window, GWLP_WNDPROC);

         SetWindowLongPtr(SDL_Window, GWLP_WNDPROC, (LONG_PTR)WinMessage);

     } else {

         SDL_Window = CreateWindow(SDL_Appname, SDL_Appname,

                        (WS_OVERLAPPED|WS_CAPTION|WS_SYSMENU|WS_MINIMIZEBOX),

                        CW_USEDEFAULT, CW_USEDEFAULT, 0, 0, NULL, NULL, SDL_Instance, NULL);

         if ( SDL_Window == NULL ) {

              SDL_SetError("Couldn't create window");

              return(-1);

         }

         ShowWindow(SDL_Window, SW_HIDE);

     }

 

     /* JC 14 Mar 2006

         Flush the message loop or this can cause big problems later

         Especially if the user decides to use dialog boxes or assert()!

     */

     WIN_FlushMessageQueue();

 

     return(0);

}

注意到前面的if條件判斷使用了SDL_windowid，如果這個變量不為0，那么SDL是不會創建新窗口的！而這個值直接來自于SDL_WINDOWID這個環境變量！以此推斷，只要在調用SDL_Init之前設置好SDL_WINDOWID這個環境變量，那么SDL將可以使用我們提供的窗口。

下面修改SDL提供的testwin示例，使之在MFC SDI環境下運行。

1.1    工程創建
直接使用VS2008的向導生成一個叫sdi_sdl的MFC工程，選擇SDI類型。

1.2    拋棄SDLmain.lib
在SDL提供的測試用例中，都要使用SDLmain.lib，這個lib文件實現了Winmain和main這兩個入口函數，在這兩個函數中進行了一些SDL的初始化工作。而在MFC下，我們不需要自己寫WinMain，因此直接拋棄SDLmain.lib，將相關的代碼轉移到Csdi_sdlView的OnCreate函數中。之所以選擇Csdi_sdlView::OnCreate是因為此時窗口已經創建，可以取到這個窗口的Handle，從而可以在SDL初始化之前設置好Window id。

int Csdi_sdlView::OnCreate(LPCREATESTRUCT lpCreateStruct)

{

     if (CView::OnCreate(lpCreateStruct) == -1)

         return -1;

 

    char variable[256];

     sprintf(variable, "SDL_WINDOWID=0x%lx", this->GetSafeHwnd());

    SDL_putenv(variable);

     SDL_WinMain(AfxGetApp()->m_hInstance, NULL, AfxGetApp()->m_lpCmdLine, SW_MAXIMIZE);

     return 0;

}

1.3    SDL_WinMain
這個函數來源于SDLmain中的WinMain函數，只是刪除了一些不必要的代碼：

/* This is where execution begins [windowed apps] */

int Csdi_sdlView::SDL_WinMain(HINSTANCE hInst, HINSTANCE hPrev, LPSTR szCmdLine, int sw)

{

     HINSTANCE handle;

     char **argv;

     int argc;

     char *cmdline;

     char *bufp;

     size_t nLen;

 

     /* Start up DDHELP.EXE before opening any files, so DDHELP doesn't

        keep them open.  This is a hack.. hopefully it will be fixed

        someday.  DDHELP.EXE starts up the first time DDRAW.DLL is loaded.

      */

     handle = LoadLibrary(TEXT("DDRAW.DLL"));

     if ( handle != NULL ) {

         FreeLibrary(handle);

     }

 

     /* Grab the command line */

     bufp = GetCommandLine();

     nLen = SDL_strlen(bufp)+1;

     cmdline = SDL_stack_alloc(char, nLen);

     SDL_strlcpy(cmdline, bufp, nLen);

 

     /* Parse it into argv and argc */

     argc = ParseCommandLine(cmdline, NULL);

     argv = SDL_stack_alloc(char*, argc+1);

     ParseCommandLine(cmdline, argv);

 

     /* Run the main program (after a little SDL initialization) */

     SDL_PreMain(argc, argv);

 

     /* Hush little compiler, don't you cry... */

     return 0;

}

1.4    SDL_PreMain
這個函數來源于sdlmain.lib中的main函數：

/* This is where execution begins [console apps] */

int Csdi_sdlView::SDL_PreMain(int argc, char *argv[])

{

     size_t n;

     char *bufp, *appname;

     int status;

 

     /* Get the class name from argv[0] */

     appname = argv[0];

     if ( (bufp=SDL_strrchr(argv[0], '\\')) != NULL ) {

         appname = bufp+1;

     } else

     if ( (bufp=SDL_strrchr(argv[0], '/')) != NULL ) {

         appname = bufp+1;

     }

 

     if ( (bufp=SDL_strrchr(appname, '.')) == NULL )

         n = SDL_strlen(appname);

     else

         n = (bufp-appname);

 

     bufp = SDL_stack_alloc(char, n+1);

     SDL_strlcpy(bufp, appname, n+1);

     appname = bufp;

 

     ///* Load SDL dynamic link library */

     //if ( SDL_Init(SDL_INIT_NOPARACHUTE) < 0 ) {

     //   ShowError("WinMain() error", SDL_GetError());

     //   return(FALSE);

     //}

 

     /* Sam:

        We still need to pass in the application handle so that

        DirectInput will initialize properly when SDL_RegisterApp()

        is called later in the video initialization.

      */

     SDL_SetModuleHandle(GetModuleHandle(NULL));

 

     /* Run the application main() code */

     status = SDL_main(argc, argv);

 

     /* Hush little compiler, don't you cry... */

     return 0;

}

1.5    SDL_main
這個函數來自于testwin示例中的main函數，只是在末尾刪除了SDL_Quit這樣的退出語句。

int Csdi_sdlView::SDL_main(int argc, char *argv[])

{

     SDL_Surface *screen;

 

     /* Options */

     int speedy, flip, nofade;

     int delay;

     int w, h;

     int desired_bpp;

     Uint32 video_flags;

 

     /* Set default options and check command-line */

     speedy = 0;

     flip = 0;

     nofade = 0;

     delay = 1;

 

     RECT rc;

     this->GetWindowRect(&rc);

     w = rc.right;

     h = rc.bottom;

     desired_bpp = 0;

     video_flags = 0;

     if ( SDL_Init(SDL_INIT_VIDEO | SDL_INIT_NOPARACHUTE) < 0 ) {

         ShowError("Couldn't initialize SDL", SDL_GetError());

         return(1);

     }

 

     /* Initialize the display */

     screen = SDL_SetVideoMode(w, h, desired_bpp, video_flags);

     if ( screen == NULL ) {

         ShowError("Couldn't set %dx%dx%d video mode: %s\n", "");

         return (1);

     }

 

     DrawPict(screen, argv[1], speedy, flip, nofade);

//   SDL_Delay(delay*1000);

//   SDL_Quit();

     return(0);

}

至此，這個程序就可以正常運行了，但是它的大小還不能隨主窗口的變化而變化。為此還需要響應WM_SIZE：

void Csdi_sdlView::OnSize(UINT nType, int cx, int cy)

{

     SDL_Surface *screen;

     screen = SDL_SetVideoMode(cx, cy, 0, 0);

     DrawPict(screen, NULL, 0, 0, 0);

}

1.6    SDL_Quit
在程序退出的時候，需要調用SDL_Quit進行一些清理的工作，原來想將這個工作放在Cview::OnDestroy中完成，但是發現這樣有很多的內存泄漏。最后將其放在Csdi_sdlApp:ExitInstance中完成：

BOOL Csdi_sdlApp::ExitInstance()

{

     SDL_Quit();

     return TRUE;

}

即便是這樣，仍然有一處內存泄漏，原因不明：

Detected memory leaks!

Dumping objects ->

{98} normal block at 0x003D37C0, 21 bytes long.

 Data: <0x40784 OWID 0x4> 30 78 34 30 37 38 34 00 4F 57 49 44 00 30 78 34

Object dump complete.

 

本文來自CSDN博客，轉載請標明出處：http://blog.csdn.net/lights_joy/archive/2009/04/04/4049123.aspx

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