Factor Inline Input 1

I want to make Factor inline input possible with CJK languages such as Japanese. So, I’m modifying it. However, I’ve got stuck.

For example, I use the return key to confirm the conversion string, but I can not operate well because the key input to IM such as return passes over to Factor.

I expected the key input to be received first by the IM, and the app received the input that was not consumed, but it seems that the IM can’t receive the input unless the Factor backend sends a key-down event.