win32 When trying to convert string to LPCWSTR, the result is Japanese characters

someone 20

I want to make what key the user presses added to a string and then displayed in SetWindowText, but the output is Chinese characters

case WM_CHAR: 
{
	ifpressed;
	static std::string getwparam;
	getwparam.push_back( wParam );
	SetWindowText(hwnd, (wchar_t*)getwparam.c_str());
	break;
}

pls help

in the settings I have Character set: multi-byte chars

i couldn't find a solution to that :<

Accepted answer

Xiaopo Yang - MSFT 12,231 Reputation points Microsoft Vendor

2024-07-24T00:48:45.8333333+00:00

Hello @someone,

First of all, according to the WM_CHAR message,

The WM_CHAR message uses UTF-16 (16-bit Unicode Transformation Format) code units in its wParam if the Unicode version of the RegisterClass function was used to register the window class. Otherwise, the system provides characters in the current process code page, which can be set to UTF-8 in Windows Version 1903 (May 2019 Update) and newer. For more information, see Registering Window Classes and Use UTF-8 code pages in Windows apps.
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RLWA32 43,461 Reputation points

2024-07-24T00:14:05.0266667+00:00

If you are building with the MBCS character set why are you trying to cast using (LPCWSTR)? If you want to use unicode then set Unicode as the character set for your project. You cannot convert to unicode with a cast. That is the reason you are seeing what appears like Japanese or Chinese characters. Also, for unicode you should use std::wstring.
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RLWA32 43,461 Reputation points

2024-07-24T06:14:57.79+00:00

Most Windows API functions that have text strings as arguments have two versions. For example, SetWindowTextA accepts non-UNICODE (narrow) strings and SetWindowTextW accepts UNICODE (wide) strings. Windows uses UTF-16LE as its native UNICODE implementation for the "W" API functions.

If you look at the documentation you will see this remark -

"Note

The winuser.h header defines SetWindowText as an alias which automatically selects the ANSI or Unicode version of this function based on the definition of the UNICODE preprocessor constant. Mixing usage of the encoding-neutral alias with code that not encoding-neutral can lead to mismatches that result in compilation or runtime errors. For more information, see Conventions for Function Prototypes."

As @Xiaopo Yang - MSFT referenced, window classes registered RegisterClassA will expect non-UNICODE strings while window classes registered using RegisterClassW will expect UNICODE strings.

Ordinarily, setting the character set property of a C++ project will cause the proper versions (A vs. W) of Windows API functions to be used. Windows also provides for generic-text mappings to simplify writing code that can build as either UNICODE or non-UNICODE. This was more common in the past but can help eliminate mismatches between the code that defines strings and the functions that accept string arguments. See Generic-Text Mappings in tchar.h. Note that the C Standard library functions also support the generic mappings.

Finally, you should avoid using casts to eliminate compiler errors. In some cases they can be useful and harmless, in other cases they are actually a lie to the compiler to avoid compilation failure that later results in execution errors such as the noted problem with Japanese/Chinese characters mysteriously appearing.

Darran Rowe 571 Reputation points

2024-07-24T14:46:49.7433333+00:00

In addition to what RLWA32 rightfully stated about casts.

Usually, it is known in advance whether a cast is the correct course of action. An example is WM_CREATE's lParam where the documentation states that it is a pointer to a CREATESTRUCT structure. This means that, depending on whether RegisterClassA or RegisterClassW was used to register the window class, it is valid to cast the lParam to CREATESTRUCTA * or CREATESTRUCTW *. If there is any question about which version of RegisterClass was used, the IsWindowUnicode function will indicate which version was used.

I would also personally recommend not using C style casts in C++. They can be unexpectedly and surprisingly destructive. It is always best to use the C++ casts, even if they require more typing. It is also best to start from static_cast, then try dynamic_cast if appropriate. If these casts do not work for the intended purpose, then const_cast and reinterpret_cast should then be considered with a lot of caution. C style casts will happily remove const and do some other bad type conversions without notification.
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win32 When trying to convert string to LPCWSTR, the result is Japanese characters

I want to make what key the user presses added to a string and then displayed in SetWindowText, but the output is Chinese characters

1 additional answer