Re: Conditionalized font-locking?

[Stephen Berman <stephen.berman@gmx.net>]

On Thu, 10 May 2012 09:30:17 -0600 Davis Herring <herring@lanl.gov> wrote:

>> (defun srb-date-time-matcher (lim)
>>   "Search for date-time strings within LIM for font-locking."
>>   (when (re-search-forward (concat "^\\(?1:[0-9][0-9][0-9][0-9]-"
>>   				   "[0-9][0-9]-[0-9][0-9]\\)"
>>   				   " \\(?2:[0-9]?[0-9]:[0-9][0-9]\\)?")
>>                            lim t)
>>     (let* ((date (match-string-no-properties 1))
>>     	   (time (match-string-no-properties 2))
>> 	   ;; days-between needs a non-empty time string.
>>     	   (date-time (concat date " " (or time "00:00"))))
>>       (when (< (days-between date-time (current-time-string)) 0)
>> 	(concat date " " time)))))
>> [...]
>>      Fontification will call FUNCTION repeatedly with the same limit,
>>      and with point where the previous invocation left it, until
>>      FUNCTION fails.  On failure, FUNCTION need not reset point in any
>>      particular way.
>
> If any of your searches turns up a date you don't like, your function
> fails (returns nil), so font-lock gives up.  You need to (unfortunately)
> write much the same loop that font-lock is wrapping around your function
> so that it finds the first date that it cares about rather than
> returning nil.

Thank you, that was the part I didn't quite understand.

> The easy way to do this if you don't have too many dates being fontified
> at one go is just to recursively call yourself when you don't like your
> current match:
>
>   (or (< ...) (srb-date-time-matcher lim))
>
> Note that you needn't return any particular non-nil value on success;
> it's the match-data that font-lock uses.

This works perfectly, thanks very much!

Steve Berman