In UNIX/Linux, language settings are environmental variables. All you would need to do is set a variable and export it before a program starts. T
But if I understand this correctly, this would cause the interface of that program to be in Japanese as well. The only thing I want to make Japanese is my input. So, for example, when I use Firefox in Windows, all the menus and buttons are in English, but when I type a search into Google, I can do so with English or Japanese characters at my discretion.
You can do either with X. You can continue to use your English keyboard _and_ you can plug in a Japanese keyboard simultaneously.
This is different from the desired functionality. I want to only need my one keyboard, my English one, and use it for English and Japanese input. As I do with Windows.
Dave