Re: Capture template and elisp expression

[Carsten Dominik <carsten.dominik@gmail.com>]

On Jan 6, 2011, at 11:26 PM, Nick Dokos wrote:

> Rainer M Krug <r.m.krug@gmail.com> wrote:
>
>>
>> Hi
>>
>> I want to use a Capture Template to record changes to files under
>> version control. Everything works as expected, but I would like to
>> include the current revision in the template.
>>
>> Therefore I tried the following:
>>
>> * %T %? at %a by Rainer M Krug, email: Rainer@krugs.de
>> %(vc-working-revision buffer-file-name)
>>
>> for the template, but I get an error:
>>
>> **** <2011-01-06 Thu 13:06>  at
>> [[file:~/Documents/Projects/BiocontrolAndAlienDynamics/ 
>> nonSpatialAcacia/trunc/R/nsa.org::*Finalise][Finalise]]
>> by Rainer M Krug, email: Rainer@krugs.de %![Error: (wrong-type- 
>> argument
>> stringp nil)]
>>
>> Any idea how I could get the revision of the org file from which the
>> Capture has been initiated (here
>> ~/Documents/Projects/BiocontrolAndAlienDynamics/nonSpatialAcacia/ 
>> trunc/R/nsa.org
>> )?
>>
>
> There are a few problems: the evaluation of the sexp happens in the
> capture buffer where buffer-file-name returns nil. Even if you could
> get the file name, vc-working-revision would return nil on a file that
> is not VC-registered and the template would barf.
>
> Those are easy problems to solve but there is another one that seems
> insurmountable (with current code): my original thought was to use the
> %a escape to pass the link to a lisp function, extract the file name
> from it[fn:1] and run vc-working-revision on it (with appropriate  
> safeguards
> to catch non-VC files), something like this:
>
> "* %T %? at %a by Rainer M Krug, email: Rainer@krugs.de        %(rk- 
> custom-function-to-get-vc-revision \"%a\")"
>
> However, this fails because at the time that %(sexp) constructs are
> expanded, simple %a etc. constructs have not been expanded yet, so  
> what
> the function above gets is a literal "%a": the subtitution sequence is
>
>            ;; %[] Insert contents of a file.
>
>            ...
>
>            ;; %() embedded elisp
>
>            ...
>
>            ;; Simple %-escapes
>
> (see lisp/org-capture.el, lines 1181-1229 or so).
>
> Moreover, this sequence was different and was changed deliberately  
> (see
> the thread http://thread.gmane.org/gmane.emacs.orgmode/27649), so if  
> it
> is changed back, Sebastion Rose will not be happy :-)
>
> So it seems there is no way to pass values from the capture context  
> to a
> lisp function in the capture template, but maybe I'm missing  
> something.
>
> Thanks,
> Nick
>
> Footnotes:
> [fn:1] Is there an easier way to get the filename of the file I was
> visiting when I initiated the capture? If not, should there be?  
> Perhaps
> a %f escape?

Hi Nick,

you can use

     (buffer-file-name (org-capture-get :original-buffer))

and we could certainly introduce a special escape for it if helpful.

If it is easier, we can also put the filename itself into the property  
list,
and any other information we like.  This should happen in the function  
org-capture,
close to the location where the buffer is stored, so near this line:

	(org-capture-put :original-buffer orig-buf :annotation annotation
			 :initial initial)

org-capture uses this property list precisely so that it is simple
to add any information required.

Note that, after the template has been filled in, it is better
to access information in the property list with


   (org-capture-get PROPERTY 'local)

to avoid conflicts with other ongoing capture processes.

Hope this helps.

- Carsten






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