Cannot detect insertion of commited composing text (i.e. press Enter) only by onInput (without state)

[tats-u]

https://w3c.github.io/uievents/tools/key-event-viewer.html

1. Enable Japanese IME
2. Type henkan
3. Space
4. Enter to commit

Firefox:

Chrome:

The current specification cannot handle 4. only by onInput without state. The onInput events corresponding to 3. and 4. are not standardized across browsers. Safari seems to fire multiple onInput events at 4 with isComposing = true.
Firefox fires an extra onInput event at 4 with isComposing = true.
It is difficult to filter out extra events related to 4.