Beamer slides from org file

Tags: / emacs org-mode tex /

Making beamer presentation slides as pdf from org files in emacs..

Beamer is a great way to make slides for presentations. It relieves us of the burden of worrying about the exact placement of elements present in the slides.

But LaTeX commands can get in the way of the actual content while we are making the slides (especially when you are in a hurry to finish it). Org mode of emacs is a cool way to make notes in an organized way that lets us focus on the content. Writing the initial draft of the presentation in org mode, then converting it to a beamer tex file and finally adding finishing touches can greatly accelerate the time in which the presentation can be created.

This post gives a broad outline of how to get started with using org mode for writing beamer presentations.

Versions of software used:

Setting up org file

We can use the export options to do stuff like setting the theme used for the beamer presentation.

For example, we can use the 'Berlin' theme with

#+LATEX_HEADER: \mode<beamer>{\usetheme{Berlin}}

Things we include in LATEX_HEADER (and LATEX_HEADER_EXTRA) will get appended to the preamble of the tex file.

LATEX_HEADER can we specified more than once if we got multiple lines to include.

Note: Export option names are case insensitive. #+LATEX_HEADER and #+latex_header are same.

We can use other export options like TITLE, AUTHOR, DATE whose purposes are evident from their names.

I use something like this as a template for the presentations that I make in org mode for use with beamer:

#+TITLE: My org-beamer presentation
#+AUTHOR: My name
#+EMAIL:  my@email.com
#+DATE:   2022-Feb-19
#+SUBTITLE: org-beamer: subtitle
#+DESCRIPTION: org-beamer: description
#+OPTIONS:  H:2
#+LATEX_HEADER: \mode<beamer>{\usetheme{Berlin}}
#+LATEX_HEADER: \AtBeginSection[]{\begin{frame}<beamer>\frametitle{Topic}\tableofcontents[currentsection]\end{frame}}

H: 2 was given as an option to mention the number of heading levels to export. Headings with level greater than 2 will be exported differently (I didn't want too many levels. Cleaner that way).

Exporting to pdf

Org-export to pdf for beamer presentations is done by ox-beamer. It's the beamer backend for the org-export engine (ox stands for org-export, I guess). So load it by adding the following to the emacs config file:

(require 'ox-beamer)

Now upon C-c C-e for exporting from an org file, we should see a few option with '(Beamer)' as well.

[l] Export to LaTeX
    [L] As LaTeX buffer           [l] As LaTeX file
    [p] As PDF file               [o] As PDF file and open
    [B] As LaTeX buffer (Beamer)  [b] As LaTeX file (Beamer)
    [P] As PDF file (Beamer)      [O] As PDF file and open (Beamer)

The Beamer options would not show up if ox-beamer isn't there.

Note that the key combination to export an org file to beamer pdf is C-c C-e l P (upper case 'P') and not C-c C-e l p (which is for exporting to non-beamer pdf).

Configuring command for pdf generation

The variable that has the command used for producing pdf from org files is org-latex-pdf-process. In old versions of emacs this was org-latex-to-pdf (notice the extra 'to' in the name)¹. There are many old blog posts mentioning this older variable name. I got confused at first.

I'm using xelatex with latexmk:

(setq org-latex-pdf-process (list "latexmk -xelatex %f"))

By default the pdflatex is used. We can set xelatex as the default latex compiler with

(setq org-latex-compiler "xelatex")

and then if we export the org file as beamer latex, it will show

% Intended LaTeX compiler: xelatex

at the beginning, instead of naming 'pdflatex'.

Latex classes

LATEX_CLASS export option is used to choose the class that we would choose using \documentclass in the tex source. For me, I didn't have to specify #+LATEX_CLASS: beamer but in the output tex file it was showing up as \documentclass[presentation]{beamer}.

(I tried using #+LATEX_CLASS: report and the tex file got \documentclass[11pt]{report}.)

We can make our own latex class to control how our org file's contents get inserted into the corresponding latex file.

The name of such custom-made latex classes should be included in the org-latex-classes variable before using it with LATEX_CLASS. ⁴

'beamer' is defined as a latex class that is added to org-latex-classes by ox-beamer itself. ⁶

Current value of org-latex-classes can be found out like any other variable in emacs. Following are two ways:

We can add a new latex class with name, say "mybeamer", like:

(add-to-list 'org-latex-classes
  `("mybeamer"   ; the name that will be used in LATEX_CLASS export option
    ,(concat "\\documentclass[presentation]{beamer}\n"
             "[DEFAULT-PACKAGES]"
             "[PACKAGES]\n")
    ("\\section{%s}" . "\\section*{%s}")
    ("\\subsection{%s}" . "\\subsection*{%s}")
    ("\\subsubsection{%s}" . "\\subsubsection*{%s}"))))

Here, contents of [DEFAULT-PACKAGES], [PACKAGES] are determined by org-latex-default-packages-alist, org-latex-packages-alist respectively.

The last three lines specify how to treat heading levels 1,2 and 3 respectively.

References