344598 - spelling checker should mark words as misspelled as soon as possible

Status: NEW

(Core :: Spelling checker, enhancement)

Description

[David Baron :dbaron: (⌚️UTC-4, no longer working on Mozilla)]

The spelling checker currently marks words as misspelled only once the word has been completed.  It could mark them as misspelled earlier:  once they're no longer the initial substring of a word in the dictionary.  This would provide quicker feedback to users (especially for those who always backspace to correct mistakes, no matter how many characters back it is).

Steps to reproduce:
 1. load this bug report
 2. click in the "Additional comments" textfield
 3. type "missspelling " (three "s"es)

Actual results:
 3. red underline appears after typing the space after the end of the word

Expected results:
 3. red underline appears after typing the third "s", since there are no words in the dictionary beginning with "misss"

Additional information:  Doing this requires some care with IME interaction.  It probably should only look at committed text, or something like that.