On 02/22/2016 11:40 AM, Eli Zaretskii wrote:
>> Cc: emacs-devel@gnu.org
>> From: Clément Pit--Claudel <clement.pit@gmail.com>
>> Date: Mon, 22 Feb 2016 11:29:10 -0500
>>
>>> I think what you describe _is_ the proper way.  Can you show a test
>>> case which demonstrates how calling font-lock-flush followed by
>>> font-lock-ensure fails to do the job?
>>
>> In any case where font-lock-fontified is nil
>> font-lock-fontify-buffer will properly refontify the whole buffer,
>> but font-lock-flush and font-lock ensure will not do anything.
> 
> That's not what I see in the code, that's why I asked for a test
> case.  I'm probably missing something.

Here's a test case:

(with-current-buffer (get-buffer-create "temp")
  (erase-buffer)
  (setq-default prettify-symbols-unprettify-at-point 'right-edge)
  (emacs-lisp-mode)
  (prettify-symbols-mode)
  (insert "lambda\n\nlambda")
  (pop-to-buffer (current-buffer)))

Moving around in this buffer unprettifies and reprettifies ‘lambda’s into ‘λ’s as the point moves in and out of them. Setting ‘font-lock-fontified’ to nil breaks that mechanism (the ‘λ’s are unprettified but no reprettified), and no series of ‘font-lock-flush’ and ‘font-lock-ensure’ will reprettify them.

Does this help?