Re: problem with font lock

[Eli Zaretskii]

> From: "Jose A. Ortega Ruiz" <address@hidden>
> Date: Fri, 15 Jan 2010 13:14:09 +0100
> 
> i'm experiencing an intermittent problem with font lock that i don't
> know how to debug (this is emacs 23.1.91 packaged for debian). every now
> and then, font lock just stops working in most (but not all) of the
> buffers: the extant colors remain, but new text is not coloured at all
> (e.g., if i comment a line out, the line's text retains its initial
> faces instead of switching to the comment face). as i said, i haven't
> found a way to reproduce this behaviour deterministically, and when it
> starts happening i don't see any error message around. so my question
> is: what would you recommend to look at when i enter this state, so that
> i can submit a useful bug report?

Did you customize font-lock or jit-lock in any way?  Does this happen
in "emacs -Q"?  If you type "M-x font-lock-fontify-buffer RET", after
e.g., commenting a line, does the fontification catch up with the
changes?

Re-fontification when the buffer is modified or scrolled is done by
jit-lock.el, and it generally runs off Emacs timers.  So anything that
prevents times from running would have the effect that you seem to
observe.