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Re: highlighting large regions (comments) with font-lock keywords
From: |
Eric Schulte |
Subject: |
Re: highlighting large regions (comments) with font-lock keywords |
Date: |
Wed, 28 Sep 2011 07:08:58 -0600 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/24.0.50 (gnu/linux) |
Stefan Monnier <address@hidden> writes:
>> I'm working on a major mode for a new language [1] which comments
>> regions between \* ... *\. I've properly (I believe) instantiated
>> font-lock keywords, and I have added a function to the
>> `font-lock-extend-region-functions' list to ensure that both ends of a
>> comment are always considered at the same time but unfortunately comment
>> highlighting often does not work.
>
>> Specifically, when I first enter a buffer and right after calling
>> `shen-mode' all comments are properly highlighted, however as I edit and
>> navigate in the buffer larger comments often lose fontification.
>
> Let's see:
>
> (defun shen-font-lock-extend-region-comment ()
> "Move fontification boundaries to contain whole comments."
> (let ((changed nil))
> (goto-char font-lock-beg)
> (when (and (re-search-forward "\\\\\\*" font-lock-end t)
> (< (match-beginning 0) font-lock-beg))
> (setq font-lock-beg (match-beginning 0)
> changed t)
> (when (and (re-search-forward "\\*\\\\" nil t)
> (> (match-end 0) font-lock-end))
> (setq font-lock-end (match-end 0)
> changed t)))
> changed))
>
> We have an obvious problem here: after (goto-char font-lock-beg) we're
> at font-lock-beg, and after (re-search-forward "\\\\\\*" font-lock-end
> t), we can only be further, so (match-beginning 0) will never be
> < font-lock-beg.
>
> BTW, why not simply do:
>
> (defvar shen-mode-syntax-table
> (let ((table (make-syntax-table)))
> (modify-syntax-entry ?- "w" table)
> (modify-syntax-entry ?\\ ". 14" table)
> (modify-syntax-entry ?* ". 23" table)
> (modify-syntax-entry ?? "w" table)
> (modify-syntax-entry ?< "w" table)
> (modify-syntax-entry ?> "w" table)
> table)
> "Syntax table to use in shen-mode.")
>
Hi Stefan,
Yes, the syntax-table method is definitely preferable. Simpler and
(more importantly) works reliably.
>
> Oh, and I haven't looked any other part of the code, but just happened
> to see:
>
> (add-to-list 'font-lock-extend-region-functions
> 'shen-font-lock-extend-region-comment t))
>
> Where the `local' arg is nil whereas it should be t (maybe the t was
> meant for `local' rather than for `append'?).
>
You're right again, I should have made font-lock-extend-region-functions
local before appending to it. Luckily this font-lock-fanciness can be
discarded now thanks to the simple syntax table fix.
Thanks for the help, much appreciated -- Eric
>
>
> Stefan
--
Eric Schulte
http://cs.unm.edu/~eschulte/