Re: Hook Function Examples

[Mark Elston <m_elston@comcast.net>]

On 1/24/2010 9:24 PM, Nick Dokos wrote:
> Mark Elston<m_elston@comcast.net>  wrote:
>
>> I am trying to make use of some of the hooks for exporting and haven't
>> found any docs about what they take or how to make use of them (elisp
>> is *not* my native language).
>>
>
> The Emacs Lisp Reference manual has a section (23.1: Hooks) on hooks,
> but I'm not sure how helpful it will be to you. The most important note
> is that "normal" hook variables are, by convention, named
> <foo>-hook. "normal" means that the functions that are added to the hook
> take no arguments and return no useful values.
>
>> In particular, I am trying to figure out how to use the following
>> to see if any of them are going to help me:
>>
>>   org-export-preprocess-hook
>>   org-export-preprocess-after-tree-selection-hook
>>   org-export-preprocess-final-hook
>>
>> Any examples of a hook function for these would help a lot.  In
>> particular, what are the parameters, is the point "looking at"
>> anything in particular, etc.
>>
>
> Use the source, Luke! (erm... Mark!)
>
>   C-h v org-export-preprocess-hook<RET>
>
> gives me:
>
>   (org-export-blocks-preprocess)
>

Thanks, Nick.  I had checked a few hooks (but not that one) and
couldn't find any that had any functions assigned.

> so we have here an example of a hook function!
>
>   C-h f org-export-blocks-preprocess<RET>
>
> gives you the function's doc string, including a link to where it is
> defined, and clicking on the link will take you to the function: no
> params (it is a "normal" hook after all), and I think you can make no
> assumptions about the context. In particular, the above function wraps
> everything in a save-excursion, goes to the beginning of the buffer and
> searches for interesting things, doing something on each interesting
> thing it finds.

OK.  From what I read I am assuming that a buffer is created with some
already-processed (though not completely) org data as its initial
content.  Then, at some point, these hook functions are called on this
new buffer.  I assume this is the case since you wouldn't want to go
modifying the original buffer - though this is not stated anywhere that
I can find.

Some hook functions apparently *do* take parameters (e.g.
org-cycle-hook, etc) and I wasn't sure about the ones that didn't
mention any.

I was just trying to find my way and didn't have a map of what was
where.  Even the org-export-blocks-preprocess()  function is a little
difficult to wade through for someone not really familiar with elisp.
I think I have pieced it together, though.  This may give me what I need
to do what I want (remove some specific kinds of headers when creating
certain LaTeX files).

Are my assumptions above correct, then?

Mark