Re: [dev] About a beamer back-end

[Nicolas Goaziou <n.goaziou@gmail.com>]

Hello,

Eric S Fraga <e.fraga@ucl.ac.uk> writes:

>> See `org-element-drag-backward' and `org-element-drag-forward'.
>
> Okay.  Will it be easy to bind these to M-<up> etc. to achieve
> consistent behaviour?  I.e. does org-metaup know what to do with
> blocks?

I hope that, one day, they will replace current `org-metaup' and
`org-metadown'.

If you want to try them out (there has been no serious debugging for
them), you can

  (defalias 'org-metaup 'org-element-drag-backward)

`org-element-drag-backward' is a strict super-set for `org-metaup'.

> As a point for discussion and evaluation, attached is an example slide
> (both org and pdf) demonstrating the type of thing I tend to do for some
> of my beamer documents.

Thanks for this example, and for feedback from other Org users.

Although more logical, it appears that the block syntax for Beamer
wouldn't be that great.  Nested blocks are hard to parse (by a human)
due to their uniform fontification (contrary to headlines, whose
fontification change at every level).

Also, the syntax is very heavy. Not more than property drawers, but, at
least, you can hide those.

I'll keep headlines for blocks.  But I think I'll introduce a couple of
small changes.

- Sectioning and packages are extracted from `org-e-latex-classes'.
  Since calling Beamer back-end is explicit, it can be applied on any
  tex file, not only when that file starts with
  "\documentclass{beamer}".  Additionally, an equivalent to
  `org-beamer-use-parts' is unnecessary.

- An headline at `org-e-beamer-frame-level' level becomes a frame,
  unless it has the "noframe" tag.  In that case, its contents are
  inserted between surrounding frames.

- Any headline above that level has a block type (depending on the
  BEAMER_env property).  Without that property, the headline is still
  a block ("\begin{block}{title}...\end{block}").

- Since above some level, everything is a block, there is no "low level
  headline" anymore.  Thus, the H:num OPTION item sets
  `org-e-beamer-frame-level'.  There's no use for BEAMER_FRAME_LEVEL
  keyword.  It also means you can't make lists out of headlines.

- An headline below `org-e-beamer-frame-level' with an "appendix" tag
  becomes an appendix part.

- An headline with a "note" tag becomes a note between frames if at
  `org-e-beamer-frame-level', within current frame otherwise.

- There is no separate syntax for \alert{} command: it is the default
  output for bold objects (i.e. *text* becomes \alert{text}).

- Obviously, all special tags specified in this list are customizable.


Unfortunately I cannot get rid of "normal" environment property.  There
is also some work to do on overlays and, perhaps, links.  But let's
start with headlines first.


Regards,

-- 
Nicolas Goaziou