Index of the token whose span contains caret (offsets start after the leading prefix — base; see
formulaPrefixLen). At a boundary the LEFT token wins — the one just typed into — so the caret
adopts the color of the character behind it. -1 when the caret is in the prefix or past the end.
Index of the token whose span contains
caret(offsets start after the leading prefix —base; see formulaPrefixLen). At a boundary the LEFT token wins — the one just typed into — so the caret adopts the color of the character behind it.-1when the caret is in the prefix or past the end.