Create multiple TextFields. Turn Chinese or Japanese input method. Input strings in a TextField (but not commit), and then move focus to another field.
The partial composing string is left along on the first TextField.

But for JDK, in the same case, the partial composing string is cleared when move focus to another field. The behavior is same as the OS native applications, e.g. WordPad.

Test programs for FX and JDK are attached.