How to change the CP_ACP(0) of windows ANSI apis in an application?

Question

I try to draw text using a dll library which has only interfaces of ANSI version encapsulated windows ANSI apis, but I need to store string data using utf-8. I don't want to convert strings using MultiByte/WideChar functions so I want an approach to change the CP_ACP in my application, so that I can input string data into ANSI apis. thanks.

ps: I don't want to change the system default codepage.

Answer 1

CP_ACP represents the system Ansi codepage. You cannot change that on a per-process or per-thread basis. It is a system-wide setting. If the DLL really is dependant on CP_ACP internally, then you have no choice but to convert your from/to UTF-8 whenever you interact with the DLL.

Answer 2

UTF8 is not a codepage, and as codepages only make sense to ANSI functions, you can't do what you're asking.

If you want to store string as UTF8, you WILL need to convert from the ANSI of your app to unicode (wide char) using MultiByteToWideChar() then use WideCharToMultiByte() to convert to UTF8.

Alternatively, update you app to use unicode/wide strings internally, and convert as needed.

Answer 3

"How to change the CP_ACP?" - "I don't (want) to change the system default codepage."

Well, you have to choose. CP_ACP is the system default codepage.

Answer 4

Starting with Windows 10 v1903, you can use the application manifest to set the active code page for a given process, which might be different from the system-wide code page :

<assembly manifestVersion="1.0" xmlns="urn:schemas-microsoft-com:asm.v1">
  <assemblyIdentity type="win32" name="..." version="6.0.0.0"/>
  <application>
    <windowsSettings>
      <activeCodePage xmlns="http://schemas.microsoft.com/SMI/2019/WindowsSettings">UTF-8</activeCodePage>
    </windowsSettings>
  </application>
</assembly>

Obviously, if you need to support older versions of Windows, the application must still be aware that CP_ACP might not be CP_UTF8 and perform any necessary conversions itself.

More details can be found in Microsoft Docs.