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Re: replacing a function with another one


From: lee
Subject: Re: replacing a function with another one
Date: Tue, 11 Mar 2014 15:25:28 +0100
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/24.3.50 (gnu/linux)

Michael Heerdegen <address@hidden> writes:

> lee <address@hidden> writes:
>
>> Sigh ... Any idea why the following does not work:
>
> Your code does something you definitely shouldn't do: your advices make
> `hi-lock-set-file-patterns' and `hi-lock-find-patterns' switch to a
> different buffer (persistently!).  When you need the context of another
> buffer, use `with-current-buffer' to switch to it temporarily.

The idea is very simple:  When patterns are to be read from another
buffer, switch to that buffer before they are being read.  Before
applying them, switch back to the original buffer.

I can´t do that with `with-current-buffer´ because two different functions
need to be advised to do it, and I can´t get add-advice to work with
:around.

Why shouldn´t I switch buffers?  They are switched back anyway.

In any case, why doesn´t it work?  Is there a way to see what´s going
on, like some debugger that allows me to run it line by line?  I really
want to know why it doesn´t work.

> Maybe the following illustration may help:
>
> (defvar-local foo)
>
> Suppose we have two buffers buffer-a and buffer-b.  buffer-a is current,
> and we want to set `foo's binding in buffer-a to `foo's value in
> buffer-b (I think this is what you try to do, more or less).  This is
> how you can do it
>
> (let (helper)    ; temporary variable (not buffer local)
>   
>   (with-current-buffer buffer-b
>     ;; set it to `foo's binding in buffer-b
>     (setq helper foo))
>   
>   ;;back in buffer-a
>   (setq foo helper))

That´s why it might be better to make a fork of hi-lock.el.  I could
modify the functions directly and add other ones I´d need.  Or maybe I
should just re-define some of the functions.

In any case, when hi-lock.el changes, what I´m doing may not work
anymore.  So what difference does it make?

> BTW, did you have a look at my example?  I think it's quite close to
> what you want to achieve.

Yes, it looks very interesting :)

One thing I haven´t been able to figure out is how hi-lock.el decides
what the lines it writes to the buffer are prepended with.  In one
buffer, it puts "// Hi-lock ...", in another one, it´s "# Hi-lock ...".
Then it searches patterns with '"\\<" hi-lock-file-patterns-prefix ":"',
and apparently it will not find patterns prepended with "//" when it
figures that they should be prepended with "#".

The regexp for a comment starter is "\s<"[1], and it is not used in the
search.  So why aren´t patterns found when an unexpected comment starter
is used with the patterns written to a buffer?


[1]: http://www.emacswiki.org/emacs/RegularExpression


-- 
Knowledge is volatile and fluid.  Software is power.



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