On 17.9.2013, at 15:24, Rasmus <rasmus@gmx.us> wrote:

> Hi Carsten,
> 
> Carsten Dominik <carsten.dominik@gmail.com> writes:
> 
>> I'd be interested to see a patch to this effect.
> 
> For now here's the filter I use and a add-to-list that hopefully
> works.  It could be turned into a general function such that
> 
>   - Certain packages are only required with certain flavors of TeX
>     (curtsy of iftex).
>   - It only applies to the preamble (e.g. I don't want it in my
>     code-blocks).
> 
> For me it works great because I can quickly check drafts with pdftex
> (which is substantially faster on my system) and switch to xelatex or
> lualatex for more serious drafts.
> 
>  (setq rasmus/org-protected-packages '(inputenc fontenc))
>  (add-to-list 'org-latex-default-packages-alist '("" "iftex" nil))
> 
>  (defun rasmus/org-latex-filter-protect-inputenc (text backend info)
>    "Make inputenc and fontenc only load when using pdflatex"
>    (when (org-export-derived-backend-p backend 'latex 'beamer)
>      (replace-regexp-in-string
>       (format  "\\(\\\\usepackage\\[.*\\]{\\(%s\\)}\\)"
>                (mapconcat 'symbol-name pank/org-protected-packages "\\|"))
>       "\\\\ifPDFTeX\\1\\\\else\\\\fi"
>       text)))
> 
>  (add-to-list 'org-export-filter-final-output-functions
>               'rasmus/org-latex-filter-protect-inputenc)
> 
> 
> The output tex file looks something like this:
> 
>  \ifPDFTeX\usepackage[utf8]{inputenc}\else\fi
>  \ifPDFTeX\usepackage[T1]{fontenc}\else\fi

Hi Rasmus,

this looks excellent.  I think we will implement this as the default behavior, but only after 8.2.
Does this capture all the possible cases, or are there more cases to consider?

- Carsten

> 
> BTW: I think the \else is redundant.
> 
> –Rasmus
> 
> --
> There are known knowns; there are things we know that we know.