This is based on Locale Remulator and SbieHide as a template, but uses local MinHook instead of Detours.

Just like LR it's very basic and doesn't cover internal window messaging, registry and some of the other APIs fully like Locale Emulator does so it may show ?s in normal dialog windows or produce other artifacts. However, it covers more than what the native Sandboxie implementation currently does with Custom Locale/LangID option.

Compile this plugin in both x86 and x64 versions.

Open the configuration of a sandbox that needs the emulation and add these lines:

InjectDll64=X:\path\to\WrapLocale_x64.dll
InjectDll=X:\path\to\WrapLocale_x86.dll

By default it emulates Japanese locale. See what other sandbox config options are available in the source for now.

WrapLocale is licensed under the MIT License.
Dependencies are under their respective licenses.