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C++ Multi-Byte - prepare string of extensions for OpenFileDialog

mynameisnafe · 2014-07-03T17:39:12

HI all, I'm having some trouble figuring out how to do this one. Assimp gives me a string, containing all the file extensions it can handle. I found some code to tokenize strings on SO and wrapped it in a function. The format of the string that is used to initialise the accepted extensions list for the OPENFILENAME structure is as follows: L"All\0*.*\0Text\*.txt\0" And so I'm trying to recreate that programatically. Which is a nightmare, as I'm trying to stick '\0' in the middle of a string. // Get a vector of extensions supported by Assimp ( assimp exts string, tokenise by ';' ) std::vector<std::string> exts = Scatterbrain::Split(extsAccepted.c_str(), ';'); //create a string with a bunch of '\0' s in it, if possible std::string extsList=""; for(size_t i = 0; i < exts.size(); i++) extsList.append(exts[i] + '\0'); // contains the first extension. CString pwszExts(extsList.c_str()); // Initialize OPENFILENAME ZeroMemory(&ofn, sizeof(ofn)); ofn.lpstrFilter = (LPCWSTR)pwszExts; // This one ... // Display the Open dialog box. if( GetOpenFileName(&ofn) == TRUE ) { ... Okay - I see one bug already: the dialog is going to say 'extension_a extension_b', instead of 'ext_name_a ext_a', but I'm happy to add blank spaces for names. how is the generation of a string L"Hello\0World\0How\0Are\0You\0' done? Thanks in advance

General and Gameplay Programming Programming

Started by mynameisnafe July 01, 2014 07:04 PM

11 comments, last by mynameisnafe 9 years, 9 months ago

Chris_F

3,030

July 01, 2014 09:49 PM

std::transform(str.begin(),str.end(),back_inserter(ext),[](char t) -> wchar_t { return t == ';' ? 0 : t; });
I don't think that's actually going to do the right thing if there's anything other than US ASCII in the original string. A simple integral promotion from a multibyte UTF-8 string into Microsoft's proprietary UCS-2 wide-character Unicode variant is a fail.

Of course, if you're restricting your somain to US ASCII, you're fine.

Microsoft hasn't used UCS-2 since Windows 2000. All modern versions of Windows use UTF-16 which is a multibyte encoding the same as UTF-8. Converting a UTF-8 string to UTF-16 is not going to make it easier to process.

http://www.utf8everywhere.org/

L. Spiro

25,818

July 01, 2014 10:27 PM

If you are going to hard-code an L"" string, you are required to use the W version of OPENFILENAME (OPENFILENAMEW) and GetOpenFileName (GetOpenFileNameW).

Never mix-and-match "", _T( "" ), and L"" strings.

The solution is to convert from UTF-8 to wide-character strings via MultiByteToWideChar() (passing CP_UTF8) and use OPENFILENAMEW and GetOpenFileNameW() to open the file.

L. Spiro