让SDL_ttf支持中文

默认情况下、莪们可以使用TTF_RenderUTF8_Blended()函数来渲染UTF8文字到视频窗口中、但由于中文windows本地环境并非unicode编码而是gbk编码、这就涉及到多字节（双字节）转换成宽字节的问题了、因此还需要用一个小函数转化一下才能输出到SDL_tff中、注意其中使用到的函数要使用到windows.h头文件

char* localeToUTF8(char* src)
{
    char* buf = NULL;
    int nRetLen = 0;
    
    wchar_t* unicode_buf = NULL;
    // *function: MultiByteToWideChar (Maps a character string to a UTF-16 (wide character) string.)
    // - UINT CodePage (Code page to use in performing the conversion. )
    //                CP_ACP: The system default Windows ANSI code page.
    // - DWORD dwFlags (Flags indicating the conversion type)
    //                0:
    // - LPCSTR lpMultiByteStr (Pointer to the character string to convert.)
    //                src: the word that you want to conver
    // - int cbMultiByte (you want to process size of lpMultiByteStr)
    //                -1:  the function processes the entire input string, including the terminating null character. when the input string
    //                            not contains terminating null character, it will failure.
    // - LPWSTR lpWideCharStr (Pointer to a buffer that receives the converted string.)
    //                NULL: no receives WideChar.
    // - int cchWideChar (size of lpWideCharStr)
    //                0: set the paramter for the function returns the required buffer size.
    // * return value : because of cchWideChar is 0, so returns the required buffer size of lpWideCharStr
    nRetLen = MultiByteToWideChar(CP_ACP, 0, src, -1, NULL, 0);
    //  allocate space for unicode_buf
    unicode_buf = (wchar_t*)malloc((nRetLen+1) * sizeof(wchar_t));
    // covert the src to utf-8, and store in unicode_buf
    MultiByteToWideChar(CP_ACP, 0, src, -1, unicode_buf, nRetLen);

    // *function: WideCharToMultiByte (Maps a UTF-16 (wide character) string to a new character string. )
    // - UINT CodePage (Code page to use in performing the conversion. )
    //                CP_UTF8: With this value set, lpDefaultChar and lpUsedDefaultChar must be set to NULL.
    // - DWORD dwFlags (Flags indicating the conversion type. )
    //                0 :
    // - LPCWSTR lpWideCharStr (Pointer to the Unicode string to convert.)
    //                unicode_buf : the word that you want to conver
    // - int cchWideChar (you want to process size of lpWideCharStr)
    //                -1: the function processes the entire input string, including the terminating null character. when the input string
    //                        not contains terminating null character, it will failure.
    // - LPSTR lpMultiByteStr (Pointer to a buffer that receives the converted string.)
    //                NULL : no receives MultiByteStr.
    // - int cbMultiByte (size of lpMultiByteStr)
    //                0: set the paramter for the function returns the required buffer size.
    // - LPCSTR lpDefaultChar (Pointer to the character to use if a character cannot be represented in the specified code page. )
    //                NULL : For the CP_UTF7 and CP_UTF8 settings for CodePage, this parameter must be set to NULL.
    // - LPBOOL lpUsedDefaultChar (Pointer to a flag that indicates if the function has used a default character in the conversion.)
    //                NULL : For the CP_UTF7 and CP_UTF8 settings for CodePage, this parameter must be set to NULL.
    nRetLen = WideCharToMultiByte(CP_UTF8, 0, unicode_buf, -1, NULL, 0, NULL, NULL);
    //  allocate space for buf
    buf = (char*)malloc(nRetLen+1);
    WideCharToMultiByte(CP_UTF8, 0, unicode_buf, -1, buf, nRetLen, NULL, NULL);

    // release space of unicode_buf
    free(unicode_buf);

    return buf;
}

在这个函数中、把字符串从多字节的ASCII编码转化成unicode的宽字节编码、又将unicode的宽字节转化成UTF8的多字节编码、因为SDL_ttf不支持宽字节编码的文字、所以中间就有了unicode作为两者的桥梁作用、转换完毕后、就可以把中间转化过程的unicode宽字节变量释放掉、这里、GBK汉字编码其实就是一种扩展的ASCII编码、

参考文章：

http://www.cnblogs.com/bombless/archive/2010/11/21/SDL-using-chinese-character.html

http://www.phpweblog.net/fuyongjie/archive/2009/03/11/6374.html

http://blog.csdn.net/shellching/article/details/5316442