Re: [dev] About a beamer back-end

[Eric S Fraga <e.fraga@ucl.ac.uk>]

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Nicolas Goaziou <n.goaziou@gmail.com> writes:

> Hello,
>
> Eric S Fraga <e.fraga@ucl.ac.uk> writes:
>
>> Well, I will have to chime in with a contrary view.  I like using
>> headlines to define blocks, and I use blocks on almost every frame.  I
>> have the following reasons for preferring a headline approach:
>>
>> - the proposed approach does not easily (at all?) cater for blocks
>>   within blocks
>
> I may be missing your point, but you can have nested blocks.  What would
> be more difficult to achieve with blocks?

Sorry!  I missed the begin...end structure for the blocks you were
proposing.  Indeed, I see no reason that your proposal does not support
a recursive nesting of blocks.

>> - ease of hiding of content: org for me is still primarily an
>>   outliner!
>
> You can hide blocks too.

but the difference is that the hidden block doesn't tell you anything
about the block itself?  that is, there is no equivalent to the text
content of a headline that is visible when the contents below the
headline are hidden.  This is possibly (?) a minor point, mind you.

>> - being able to re-arrange content in a frame quickly (M-<up>, etc.)
>
> 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?

>> - within frames, there is no other use for lower level headlines.  Using
>>   these for blocks seems appropriate.  What else could they be used
>>   for?
>
> Good question.
>
> One idea would be to use them as outline tools that would have no impact
> on export (they would help hiding frame contents in the buffer but would
> be ignored in produced LaTeX code).
>
>
> Obviously, both approaches (blocks or headlines) have drawbacks.  I'm
> still unsure about which one would be the quickest/cleanest/most useful.

Understood!  And I don't want to stand in the way of an implementation
of beamer support in the new exporter.

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.

Also, please don't forget about columns!


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#+title: Blocks in beamer via org
#+author: Eric S Fraga
#+startup: beamer
#+LaTeX_CLASS: beamer
#+LaTeX_CLASS_OPTIONS: [presentation]
#+OPTIONS:   H:5 num:t toc:nil \n:nil @:t ::t |:t ^:t -:t f:t *:t <:t
#+OPTIONS:   TeX:t LaTeX:t skip:nil d:nil todo:t pri:nil tags:nil

#+BEAMER_FRAME_LEVEL: 2

#+startup: oddonly
#+startup: fninline
#+ BEAMER_HEADER_EXTRA: \usetheme{Madrid}\usecolortheme{default}
#+ latex_header: \usepackage[absolute,overlay]{textpos}\setlength{\TPHorizModule}{1mm}\setlength{\TPVertModule}{1mm}\newcommand{\UCL}{\begin{textblock}{14}(120.0,0.0)\pgfuseimage{ucllogo}\end{textblock}}
#+latex_header: \mode<beamer>{\usetheme{progressbar}}

#+latex_header: \usepackage{tikz}
* Test
*** Nested blocks
    :PROPERTIES:
    :BEAMER_envargs: [t]
    :END:
    Use distillation for separation of two components.
***** The problem                                     :BMCOL:B_ignoreheading:
      :PROPERTIES:
      :BEAMER_col: 0.3
      :BEAMER_env: ignoreheading
      :END:
******* Equilibrium                                            :B_definition:
        :PROPERTIES:
        :BEAMER_env: definition
        :END:
        \( \displaystyle y = \frac{\alpha x} {1 + (\alpha -1) x} \)
******* Goal                                                        :B_block:
        :PROPERTIES:
        :BEAMER_env: block
        :END:
        Minimise energy consumption
***** Distillation                                          :BMCOL:B_example:
      :PROPERTIES:
      :BEAMER_col: 0.6
      :BEAMER_env: example
      :END:
      #+begin_center
      #+attr_latex: width=0.9\textwidth
      [[file:~/s/figures/teaching/introduction/distillation-unit.pdf]]
      #+end_center

      \vfill
***** Approach                                        :BMCOL:B_ignoreheading:
      :PROPERTIES:
      :BEAMER_col: 1.0
      :BEAMER_env: ignoreheading
      :END:

      \vfill

      We will use the @McCabe-Thiele@ method for the initial design.

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