Re: LaTeX export of section links

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

Hi Francesco,

On Nov 20, 2009, at 12:34 PM, Francesco Pizzolante wrote:

> Hi,
>
> I have a few questions about links to sections.
>
> I've read that it is better to user IDs and CUSTOM_IDs to links to  
> section...
>
> Here's a small example with 4 cases:
>
> --8<---------------cut here---------------start------------->8---
> * First
>  :PROPERTIES:
>  :CUSTOM_ID: heading-a
>  :END:
>
>  Hello Toto!
>
> * Second
> # <<heading-b>>
>
>  Hello Tata!
>
> * Third
> #+CUSTOM_ID: heading-c
>
>  Hello Titi!
>
> * Fourth
> #+ID: heading-d
>
>  Hello Tete!
>
> [[heading-a]]
> [[heading-b]]
> [[heading-c]]
> [[heading-d]]
> --8<---------------cut here---------------end--------------->8---
>
> Which give the following LaTeX code:
>
> --8<---------------cut here---------------start------------->8---
> \section{First}
> \label{sec-1}
> \label{heading-a}
>
>
>  Hello Toto!
>
> \section{Second}
> \label{sec-2}
> \label{heading-b}
>
>
>  Hello Tata!
>
> \section{Third}
> \label{sec-3}
>
>
>  Hello Titi!
>
> \section{Fourth}
> \label{sec-4}
>
>
>  Hello Tete!
>
> \hyperref[sec-1]{heading-a}
> \hyperref[sec-2]{heading-b}
> \hyperref[sec-3]{heading-c}
> \hyperref[sec-4]{heading-d}
> --8<---------------cut here---------------end--------------->8---
>
> The first and second cases both generate labels which are not used  
> in LaTeX.

There is no harm in defining labels that are not used.

>
> The third and fourth cases are very elegant as they use only aliases  
> (which
> are dropped from the LaTeX code).

Third and forth are non-existent syntax in Org, these lines are just  
treated as comments and are removed during export.

>
> My questions are:
>
> - what's the difference between using ID and CUSTOM_ID?

Custom ID is human-readable, ID is usually a sha1 hash.  ID's have
the advantage that in HTML, they can link from one file to another
one.

> - the cases "Third" and "Fourth" are the more elegant from my point  
> of view.
>  Is this the right way of doing?

No, see above

>
> - what's the difference between cases "First" and "Second" (I mean  
> between
>  using PROPERTIES and # <<X>>)?

Only in the way that the property might be conceived as cleaner - but  
this
is really a matter of taste at this point.

>
> - in the documentation (section 4.2), we talk about "CUSTOM_ID  
> property" does
>  it mean that we should use it as in case 1?

Yes.

HTH

- Carsten