[Top][All Lists]

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: jit-lock refontifies too much

From: Richard M. Stallman
Subject: Re: jit-lock refontifies too much
Date: Sat, 24 Sep 2005 22:40:40 -0400

    - Syntactic context is correctly established via the face property
       assigned to a character by font-lock.  As an example, font-lock
       assigns a character the font-lock-string-face property iff that
       character is within a string - according to the best knowledge of

It might be worth doing this for the first character of a line, only.
That would bound the extent of refontification, but without wasting]
lots of space for text properties.

In the code that you wrote, are these properties put on characters at
the start of a line, or could they appear anywhere?

    There is one complication: When text has not been fontified yet, the
    comparison described above would always indicate a context change.

I do not understand that statement.  When the subsequent text has
not been fontified yet, it certainly needs to be fontified.
So what is it that you perceive as a problem?

Stefan wrote:

    Adding yet-another-text-property is a waste of precious CPU and
    memory resources.  It makes your suggestion pretty dubious.  Luckily, using
    syntax-ppss instead of faces should not suffer from this same initialization

How does syntax-ppss avoid the need to scan too far?
(I know you told me before, but I don't remember.)
I wonder if use of syntax-ppss will be faster than
the refontifications it saves.

You wrote:

    I'm only comparing Emacs-22.1 jit-lock with my patch.  On a 1GHz machine
    setting jit-lock-context-time to zero seconds makes Emacs stutter when I
    use auto-repeat to insert a sequence of characters.

jit-lock-context-time is not normally zero.  So what exactly is the
goal of your proposal?  Is the goal to make jit-lock-context-time zero
without loss of performance?

     > The above problems can be "easily" addressed by changing your algorithm 
     > not look at the face property, but instead to look at the return value of
     > syntax-ppss.  If it hasn't changed, then we know the subsequent text 
     > need refontification.

    I don't remember any previous return value when refontifying.  Calling
    syntax-ppss twice for the same position in one and the same invocation
    of jit-lock-fontify-now always yields the same value.

    The property would last only as long as there are unhandled buffer
    changes.  However, it does waste resources.  Too bad that syntax-ppss
    won't work.

I don't understand that response.

Stefan wrote:

    Oh, right, when jit-lock-fontify-now gets called, the buffer is already
    changed, so you'd have to use a before-change-functions hook to remember the
    syntax-ppss state before the change.  Hmmm...

You'd have to cache the syntax-ppss value in a text property, perhaps
for the first char on a line.

reply via email to

[Prev in Thread] Current Thread [Next in Thread]