std::string to const WCHAR*

[Jorgen Sigvardsson]

Naw, more likely using CA2CW or something along those lines. My bet's on that David's a bit too experienced to fall for the (wchar_t*)str.c_str() and similar newbie mistakes. :)

[Jorgen Sigvardsson]

If you are using a fairly new version of MFC (7, 8), you can use the conversion classes such as CA2W without any hassles. Just include atlconv.h in stdafx.h, and you're set.

-- Not a substitute for human interaction

[Jorgen Sigvardsson]

Stick^ wrote:

WideCharToMultiByte(CP_ACP, 0, m_ac.c_str(), -1, str, wcslen(str)+1, NULL, NULL);

Please use MultiByteToWideChar() instead. You are converting from char to wchar_t, right?

wchar_t buf[20+1] = { 0 };
MultiByteToWideChar(CP_ACP, MB_PRECOMPOSED, m_ac.c_str(), m_ac.size(), buf, 20);

should do the trick.

-- From the Makers of Futurama

[David Crow]

James R. Twine wrote:

The const char* returned by c_str() is not a wide string,...

So what exactly does std::wstring::c_str() return?

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"Approved Workmen Are Not Ashamed" - 2 Timothy 2:15

"Judge not by the eye but by the heart." - Native American Proverb

[James R Twine]

std::**w**string::c_str() returns a const WCHAR* (const wchar_t*), but not std::string:c_str(), which is what the OP was asking about.    I think that we (I?) are just getting confused about what "width" of string object is in use here.  The OP is dealing with having a std::string (ANSI) object and needs to get a (presumably valid) const WCHAR* (Unicode) out of it.    Since they cannot simply change the strings from std::string to std::wstring, they are stuck with ANSI string objects, and no amount of casting is going to create a valid wide string from the return of std::string:c_str().   They need to call a conversion function (either directly or indirectly) in order to translate the string correctly.    Peace!

-=- James

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[David Crow]

James R. Twine wrote:

std::wstring::c_str() returns a const WCHAR* (const wchar_t*)...

Which is why I suggested it as a better solution here.

James R. Twine wrote:

...no amount of casting is going to create a valid wide string from the return of std::string:c_str().

Agreed. :-O Blunder on my part.

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"Approved Workmen Are Not Ashamed" - 2 Timothy 2:15

"Judge not by the eye but by the heart." - Native American Proverb

[Zac Howland]

You are compiling with UNICODE defined, so DrawString is mapped to DrawStringW (which takes wide characters). Since you have a string (which are ANSI characters), you need to convert that string to a wstring (or simply to an array of wchar_t's). You'll need to muse MultiByteToWideChar for that (not WideCharToMultiByte).

If you decide to become a software engineer, you are signing up to have a 1/2" piece of silicon tell you exactly how stupid you really are for 8 hours a day, 5 days a week Zac

[Stick]

Thanks all for your help. I'm such an idiot, using the wrong function! I'll try all these good suggestions and do some more reading and see if I can't figure out more.

[Stick]

Thanks. Would help if I followed everyone's directions!

[James R Twine]

Actually, the OP is using the GDI+ classes, and they tend to always accept wide strings, and not have A or W versions of functions that are aliased-to depending on the build.  For example, GDI+'s three versions of the Graphics::DrawString(...) function all take a const WCHAR* as the string type.    Peace!

-=- James

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If you think it costs a lot to do it right, just wait until you find out how much it costs to do it wrong!
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