Re: jit-lock doesn't honor font-lock-lines-before

[Stefan Monnier <monnier@iro.umontreal.ca>]

> In `font-lock-default-fontify-region', immediately before the comment

>            ;; check to see if we should expand the beg/end area for
>            ;; proper multiline matches

> insert either

>            (setq beg (line-beginning-position (1- font-lock-lines-before)))

Oh, I see we violently agree.  I've committed the change.

> or - but this would have to be mentioned in the doc-string of
> `font-lock-lines-before' -

>            (when font-lock-multiline
>              (setq beg (line-beginning-position (1- font-lock-lines-before))))

I'd rather not force people to use font-lock-multiline at the same time as
font-lock-lines-before since they interact in non-trivial ways.
I'd actually rather recommend to avoid using the two together.

> remove the corresponding line from `font-lock-after-change-function' and
> wait what happens?  I'm still sceptical, though ... fontifications would
> always overlap by `font-lock-lines-before' lines.

The default setting of font-lock-lines-before makes it a nop (as it
should).  Major modes which rely on it should set it to the
appropriate value.


        Stefan