Re: Is there something like `on-display-functions'?

[Alan Mackenzie]

HI, Stefan,

On Fri, Jan 29, 2010 at 01:13:42PM -0500, Stefan Monnier wrote:
> > jit-lock-register's function only gets called when font lock is
> > enabled,

> No: jit-lock has nothing to do with font-lock, except for the fact that
> font-lock is its main client (and that historically jit-lock was
> written only for font-lock), so it's naturally tuned towards serving
> font-lock better than other potential clients.

Is this nothing-to-do-with-ness documented anywhere?  In the elisp
manual, jit-lock is found twice, both occurrences in "Other Font Lock
Variables".  Without reading the source code in great detail, you'd be
hard pressed to find out that the jit-lock mechanism is operative when
font-lock mode is disabled.

> I.e. jit-lock-register's function will be called regardless of whether
> font-lock is enabled or not.

> > or at least that's what the fine manual says and the doc string
> > implies.

> The docstring doesn't mention font-lock.

It mentions "fontification".  Isn't that a synonym for font-lock?  Or is
it the part of redisplay that converts characters into glyphs and pixels,
regardless of whether font-lock is enabled?

jit-lock-register says that FUN is "registered as a fontification
function".  I think Somebody (tm) could usefully separate out jit-lock
from font-lock in the doc strings and manual.

Just as a matter of interest, how does jit-lock know the END parameter
which it passes to FUN?  Or is this just a random value, a few hundred
bytes after BEG?

>         Stefan

-- 
Alan Mackenzie (Nuremberg, Germany).