# Local IspellDict: en
#+Title: Introduction to org-re-reveal
#+Author: Yujie Wen and others

#+KEYWORDS: org mode, reveal.js, presentation, HTML, slide show, org-re-reveal, emacs-reveal, OER
#+DESCRIPTION: Readme for org-re-reveal to generate HTML/reveal.js presentations from Org mode source files.

# SPDX-License-Identifier: GPL-3.0-or-later
# Authors: Yujie Wen <yjwen.ty@gmail.com> and contributors to
#          org-reveal and org-re-reveal, see there:
#          https://github.com/yjwen/org-reveal/commits/master
#          https://gitlab.com/oer/org-re-reveal/commits/master

# Copyright (C) 2013-2018 Yujie Wen and contributors to org-reveal, see:
#                         https://github.com/yjwen/org-reveal/commits/master
# Copyright (C) 2017-2019 Jens Lechtenbörger
# Copyright (C) 2019      Ayush Goyal <perfectayush@gmail.com>

#+OPTIONS: reveal_center:t reveal_progress:t reveal_history:nil reveal_control:t
#+OPTIONS: reveal_rolling_links:t reveal_keyboard:t reveal_overview:t num:nil
#+OPTIONS: reveal_width:1400 reveal_height:1000
#+OPTIONS: toc:1
#+OPTIONS: reveal_klipsify_src:t
#+REVEAL_MIN_SCALE: 1.0
#+REVEAL_MAX_SCALE: 1.0
#+REVEAL_PLUGINS: (notes search zoom)
#+REVEAL_MARGIN: 0.1
#+REVEAL_TRANS: cube
#+REVEAL_THEME: black
#+REVEAL_HLEVEL: 2
#+REVEAL_HEAD_PREAMBLE: <meta name="description" content="Org-re-reveal Introduction.">
#+REVEAL_POSTAMBLE: <p> Based upon work by yjwen. </p>
#+REVEAL_EXTRA_CSS: ./local.css

* Note

The project /org-re-reveal/ is a
[[https://github.com/lechten/org-reveal][fork of org-reveal]].
It provides an export back-end for HTML presentations with
[[https://revealjs.com/][reveal.js]] from
[[https://orgmode.org/][Org mode]] source files.

For a /reveal.js/ presentation for
[[https://gitlab.com/oer/org-re-reveal/blob/master/Readme.org][this Readme (which is written in the lightweight markup language Org mode)]],
see there: [[https://oer.gitlab.io/org-re-reveal/]]

** Emacs-reveal
If you are interested in /org-re-reveal/, I suggest that you take
a look at [[https://gitlab.com/oer/emacs-reveal][emacs-reveal]], which
embeds /org-re-reveal/, /reveal.js/, and useful
plugins as submodules, combined with suitable Emacs configuration.
A [[https://gitlab.com/oer/emacs-reveal-howto][Howto for the generation of reveal.js presentations (slides with audio) with emacs-reveal]]
exists as well.

I use /emacs-reveal/ to generate Open Educational Resources (OER), and
macros coming with /emacs-reveal/ simplify license attribution for
embedded figures considerably:
[[https://oer.gitlab.io/OS/][OER presentations for a course on operating systems]]

** Relationships between packages

| Package                                                           | Description                                                                                                                                          |
|-------------------------------------------------------------------+------------------------------------------------------------------------------------------------------------------------------------------------------|
| [[https://github.com/yjwen/org-reveal][org-reveal]]               | Origin of org-re-reveal                                                                                                                              |
| [[https://gitlab.com/oer/org-re-reveal][org-re-reveal]]           | Fork of org-reveal, initially to add audio fragments, now with [[https://gitlab.com/oer/org-re-reveal/blob/master/CHANGELOG.org][various changes]]   |
| [[https://gitlab.com/oer/org-re-reveal-ref][org-re-reveal-ref]]   | Addon to org-re-reveal for bibliography slide based on [[https://github.com/jkitchin/org-ref][org-ref]]                                              |
| [[https://gitlab.com/oer/oer-reveal][oer-reveal]]                 | Export backend derived from org-re-reveal; functionality for installation of reveal.js and plugins; simplification of licensing for OER              |
| [[https://gitlab.com/oer/emacs-reveal/][emacs-reveal]]            | Bundling of org-re-reveal, org-re-reveal-ref, and oer-reveal                                                                                         |

Originally, /emacs-reveal/ was created to enhance /org-reveal/, and it
contained the code of what is now maintained separately as
/org-re-reveal-ref/ and /oer-reveal/.  Those packages were separated
to make as much of /emacs-reveal/ available on MELPA as possible.
Whether anyone wants to use those package in isolation is up to them.

** Changelog
   See file [[https://gitlab.com/oer/org-re-reveal/tree/master/CHANGELOG.org][CHANGELOG]]
   for changes of org-re-reveal compared to org-reveal and onward

** Side note: Customization of variables
   - GNU Emacs can be customized in various ways, and /org-re-reveal/
     is no exception in that regard.
     - This Readme frequently suggests “to customize” some variables.
   - You may want to read the
     [[https://www.gnu.org/software/emacs/manual/html_node/emacs/Customization.html][manual entry on customization]].
   - As shortcut
     - Type ~C-h v~ (which means press the ~Ctrl~ key and ~h~
       simultaneously, then ~v~).  You are asked for a variable name.
       Enter it, e.g., ~org-re-reveal-script-files~.  You wind up in a
       help buffer, showing the current value and a “customize” link.
       Enter/press the link, leading to a customization buffer, where
       you can change the value and “Apply” (or “Apply and
       Save”) it.

* Reveal.js and org-re-reveal

  - [[https://revealjs.com/][Reveal.js]] is a tool for creating
    good-looking HTML presentations, authored by
    [[https://hakim.se/][Hakim El Hattab]].
  - Org-re-reveal exports your [[https://orgmode.org/][Org mode]]
    documents to reveal.js presentations.

    With org-re-reveal, you can create beautiful presentations with 3D
    effects from simple but powerful Org contents.

* Requirements and Installation

  - Reveal.js
  - GNU Emacs, version 24.4 or later
  - Org mode
  - Org-re-reveal
  - Htmlize or highlight.js
    - For source code highlighting, which is explained below
      - Depending on your version of Org mode, htmlize.el may be
        necessary even if you want to use highlight.js

** Install reveal.js

   *Note:* This is only necessary if you do not use [[https://gitlab.com/oer/emacs-reveal][emacs-reveal]],
   which installs and configures reveal.js with several of it plugins.

   Download reveal.js packages from [[https://github.com/hakimel/reveal.js/][here]].

   Extract reveal.js folders from the downloaded zip file.

   If you do not wish to download reveal.js yourself and would rather get a copy from a CDN,
   see the section [[https://gitlab.com/oer/org-re-reveal#set-the-location-of-revealjs][Set the location of reveal.js]]

** Install org-re-reveal from MELPA

   Package org-re-reveal is available on MELPA.  Use of MELPA requires
   some setup code in your ~.emacs~ file.
   See [[https://melpa.org/#/getting-started][here how to get started with MELPA]].

   This package defines the Org export back-end ~re-reveal~.  As usual
   for export back-ends, you can either customize
   ~org-export-backends~ to include ~re-reveal~ or add the following
   to your ~.emacs~ file.
   #+BEGIN_SRC lisp
   (require 'org-re-reveal)
   #+END_SRC

** Install org-re-reveal from GitLab

   You can download org-re-reveal as archive from GitLab
   ([[https://gitlab.com/oer/org-re-reveal/-/archive/master/org-re-reveal-master.zip][zip archive]]
   and several ~tar~ variants; note the download icon on the
   [[https://gitlab.com/oer/org-re-reveal][project page]]).

   Alternatively, you can clone the
   [[https://gitlab.com/oer/org-re-reveal][repository of org-re-reveal]]:
   #+BEGIN_SRC sh
   git clone https://gitlab.com/oer/org-re-reveal.git
   #+END_SRC

   Add the directory of =org-re-reveal.el= to your Emacs's ~load-path~, and add the
   following statement to your =.emacs= file.
   #+BEGIN_SRC lisp
   (require 'org-re-reveal)
   #+END_SRC

   *Note*: It is suggested to use a recent version of Org mode with
   org-re-reveal.  [[https://orgmode.org/][Installation of Org mode.]]

* Configuration

** Options and Plug-ins

   All options, keywords, and customizable variables of org-re-reveal are
   shown in the following table, with hints on the next slide.

| Option                            | Keyword                                      | Variable                                 |
|-----------------------------------+----------------------------------------------+------------------------------------------|
| ~reveal_center~                   | ~nil~                                        | ~org-re-reveal-center~                   |
| ~reveal_control~                  | ~nil~                                        | ~org-re-reveal-control~                  |
| ~reveal_defaulttiming~            | ~nil~                                        | ~org-re-reveal-defaulttiming~            |
| ~reveal_fragmentinurl~            | ~nil~                                        | ~org-re-reveal-fragmentinurl~            |
| ~reveal_generate_ids~             | ~nil~                                        | ~org-re-reveal-generate-custom-ids~      |
| ~reveal_hashonebasedindex~        | ~nil~                                        | ~org-re-reveal-hashonebasedindex~        |
| ~reveal_height~                   | ~nil~                                        | ~org-re-reveal-height~                   |
| ~reveal_history~                  | ~nil~                                        | ~org-re-reveal-history~                  |
| ~reveal_inter_presentation_links~ | ~nil~                                        | ~org-re-reveal-inter-presentation-links~ |
| ~reveal_keyboard~                 | ~nil~                                        | ~org-re-reveal-keyboard~                 |
| ~reveal_klipsify_src~             | ~nil~                                        | ~org-re-reveal-klipsify-src~             |
| ~reveal_mousewheel~               | ~nil~                                        | ~org-re-reveal-mousewheel~               |
| ~reveal_overview~                 | ~nil~                                        | ~org-re-reveal-overview~                 |
| ~reveal_pdfseparatefragments~     | ~nil~                                        | ~org-re-reveal-pdfseparatefragments~     |
| ~reveal_progress~                 | ~nil~                                        | ~org-re-reveal-progress~                 |
| ~reveal_rolling_links~            | ~nil~                                        | ~org-re-reveal-rolling-links~            |
| ~reveal_single_file~              | ~nil~                                        | ~org-re-reveal-single-file~              |
| ~reveal_global_footer~            | ~nil~                                        | ~org-re-reveal-global-footer~            |
| ~reveal_global_header~            | ~nil~                                        | ~org-re-reveal-global-header~            |
| ~reveal_slide_number~             | ~nil~                                        | ~org-re-reveal-slide-number~             |
| ~reveal_toc_footer~               | ~nil~                                        | ~org-re-reveal-toc-footer~               |
| ~reveal_subtree_with_title_slide~ | ~nil~                                        | ~org-re-reveal-subtree-with-title-slide~ |
| ~reveal_width~                    | ~nil~                                        | ~org-re-reveal-width~                    |
| ~nil~                             | ~REVEAL_ACADEMIC_TITLE~                      | ~nil~                                    |
| ~nil~                             | ~REVEAL_CODEMIRROR_CONFIG~                   | ~org-re-reveal-klipse-codemirror~        |
| ~nil~                             | ~REVEAL_DEFAULT_FRAG_STYLE~                  | ~org-re-reveal-default-frag-style~       |
| ~nil~                             | ~REVEAL_DEFAULT_SLIDE_BACKGROUND~            | ~nil~                                    |
| ~nil~                             | ~REVEAL_DEFAULT_SLIDE_BACKGROUND_SIZE~       | ~nil~                                    |
| ~nil~                             | ~REVEAL_DEFAULT_SLIDE_BACKGROUND_POSITION~   | ~nil~                                    |
| ~nil~                             | ~REVEAL_DEFAULT_SLIDE_BACKGROUND_REPEAT~     | ~nil~                                    |
| ~nil~                             | ~REVEAL_DEFAULT_SLIDE_BACKGROUND_TRANSITION~ | ~nil~                                    |
| ~nil~                             | ~REVEAL_EXTERNAL_PLUGINS~                    | ~org-re-reveal-external-plugins~         |
| ~nil~                             | ~REVEAL_EXTRA_ATTR~                          | ~org-re-reveal-extra-attr~               |
| ~nil~                             | ~REVEAL_EXTRA_CSS~                           | ~org-re-reveal-extra-css~                |
| ~nil~                             | ~REVEAL_EXTRA_JS~                            | ~org-re-reveal-extra-js~                 |
| ~nil~                             | ~REVEAL_EXTRA_OPTIONS~                       | ~org-re-reveal-extra-options~            |
| ~nil~                             | ~REVEAL_EXTRA_SCRIPTS~                       | ~org-re-reveal-extra-scripts~            |
| ~nil~                             | ~REVEAL_HEAD_PREAMBLE~                       | ~org-re-reveal-head-preamble~            |
| ~nil~                             | ~REVEAL_INIT_SCRIPT~                         | ~org-re-reveal-init-script~              |
| ~nil~                             | ~REVEAL_HIGHLIGHT_CSS~                       | ~org-re-reveal-highlight-css~            |
| ~nil~                             | ~REVEAL_HIGHLIGHT_URL~                       | ~org-re-reveal-highlight-url~            |
| ~nil~                             | ~REVEAL_HLEVEL~                              | ~nil~                                    |
| ~nil~                             | ~REVEAL_KLIPSE_CSS_URL~                      | ~org-re-reveal-klipse-css~               |
| ~nil~                             | ~REVEAL_KLIPSE_EXTRA_CONFIG~                 | ~org-re-reveal-klipse-extra-config~      |
| ~nil~                             | ~REVEAL_KLIPSE_JS_URL~                       | ~org-re-reveal-klipse-js~                |
| ~nil~                             | ~REVEAL_KLIPSE_SETUP~                        | ~org-re-reveal-klipse-setup~             |
| ~nil~                             | ~REVEAL_MARGIN~                              | ~org-re-reveal-margin~                   |
| ~nil~                             | ~REVEAL_MATHJAX_URL~                         | ~org-re-reveal-mathjax-url~              |
| ~nil~                             | ~REVEAL_MAX_SCALE~                           | ~org-re-reveal-max-scale~                |
| ~nil~                             | ~REVEAL_MIN_SCALE~                           | ~org-re-reveal-min-scale~                |
| ~nil~                             | ~REVEAL_MISCINFO~                            | ~nil~                                    |
| ~nil~                             | ~REVEAL_MULTIPLEX_ID~                        | ~org-re-reveal-multiplex-id~             |
| ~nil~                             | ~REVEAL_MULTIPLEX_SECRET~                    | ~org-re-reveal-multiplex-secret~         |
| ~nil~                             | ~REVEAL_MULTIPLEX_SOCKETIO_URL~              | ~org-re-reveal-multiplex-socketio-url~   |
| ~nil~                             | ~REVEAL_MULTIPLEX_URL~                       | ~org-re-reveal-multiplex-url~            |
| ~nil~                             | ~REVEAL_PLUGINS~                             | ~org-re-reveal-plugins~                  |
| ~nil~                             | ~REVEAL_POSTAMBLE~                           | ~org-re-reveal-postamble~                |
| ~nil~                             | ~REVEAL_PREAMBLE~                            | ~org-re-reveal-preamble~                 |
| ~nil~                             | ~REVEAL_ROOT~                                | ~org-re-reveal-root~                     |
| ~nil~                             | ~REVEAL_SCRIPT_FILES~                        | ~org-re-reveal-script-files~             |
| ~nil~                             | ~REVEAL_SLIDE_HEADER~                        | ~org-re-reveal-slide-header~             |
| ~nil~                             | ~REVEAL_SLIDE_FOOTER~                        | ~org-re-reveal-slide-footer~             |
| ~nil~                             | ~REVEAL_SPEED~                               | ~org-re-reveal-transition-speed~         |
| ~nil~                             | ~REVEAL_TALK_QR_CODE~                        | ~nil~                                    |
| ~nil~                             | ~REVEAL_TALK_URL~                            | ~nil~                                    |
| ~nil~                             | ~REVEAL_THEME~                               | ~org-re-reveal-theme~                    |
| ~nil~                             | ~REVEAL_TITLE_SLIDE~                         | ~org-re-reveal-title-slide~              |
| ~nil~                             | ~REVEAL_TITLE_SLIDE_BACKGROUND~              | ~nil~                                    |
| ~nil~                             | ~REVEAL_TITLE_SLIDE_STATE~                   | ~nil~                                    |
| ~nil~                             | ~REVEAL_TITLE_SLIDE_TIMING~                  | ~nil~                                    |
| ~nil~                             | ~REVEAL_TITLE_SLIDE_BACKGROUND_SIZE~         | ~nil~                                    |
| ~nil~                             | ~REVEAL_TITLE_SLIDE_BACKGROUND_POSITION~     | ~nil~                                    |
| ~nil~                             | ~REVEAL_TITLE_SLIDE_BACKGROUND_REPEAT~       | ~nil~                                    |
| ~nil~                             | ~REVEAL_TITLE_SLIDE_BACKGROUND_TRANSITION~   | ~nil~                                    |
| ~nil~                             | ~REVEAL_TOC_SLIDE_STATE~                     | ~nil~                                    |
| ~nil~                             | ~REVEAL_TOC_SLIDE_CLASS~                     | ~nil~                                    |
| ~nil~                             | ~REVEAL_TOC_SLIDE_TITLE~                     | ~org-re-reveal-toc-slide-title~          |
| ~nil~                             | ~REVEAL_TRANS~                               | ~org-re-reveal-transition~               |

#+REVEAL: split
   For documentation of variables, see their doc strings.  E.g.,
   either invoke ~C-h v~ followed by the name of the variable or
   browse the customization group ~org-export-re-reveal~: enter
   ~M-x customize-group~, then ~org-export-re-reveal~.

   For examples, please refer to the heading part of this document
   and to [[https://gitlab.com/oer/org-re-reveal/tree/master/test-cases][test-cases in the GitLab repository]].

   Options and keywords that do not have a variable documenting their
   effects are explained in this document.  Search in reveal.js
   presentations is invoked with ~C-S-f~ (which means “Control” and
   “Shift” and “f”; curiously, “f” is shown as “F” on keyboards, which
   actually is “Shift f”).

   Note that =#+REVEAL_EXTRA_OPTIONS: your_comma_separated_options=
   and =org-re-reveal-extra-options= allow to specify all
   [[https://github.com/hakimel/reveal.js/#configuration][configuration options of reveal.js]].


** Set the location of reveal.js

   org-re-reveal must know where reveal.js is on your computer before
   exporting Org contents.  You do not have to worry about any of this with
   [[https://gitlab.com/oer/emacs-reveal][emacs-reveal]].

   The location of reveal.js is the path to
   the top directory of the reveal.js packages, the directory which contains
   file ~README.md~, but *not* the one that contains the file reveal.js.

   The default location is =./reveal.js=, relative to the Org file.

   Customize =org-re-reveal-root= to change the location
   globally, or use keyword =REVEAL_ROOT= in an individual Org file.
   For example, add the following statement to your .emacs file:
#+BEGIN_SRC lisp
(setq org-re-reveal-root "file:///d:/reveal.js")
#+END_SRC

#+REVEAL: split
   *IMPORTANT*: If you use absolute paths to reveal.js as illustrated
   above, they should be in URL form,
   ~file:///path_to_reveal.js~.

   #+BEGIN_SRC org
   ,#+REVEAL_ROOT: file:///d:/reveal.js
   #+END_SRC

   You can also set =REVEAL_ROOT= to a URL to use reveal.js from
   the web instead of downloading a local copy.  The reveal.js
   documentation does not recommend this, though.

   #+BEGIN_SRC org
   ,#+REVEAL_ROOT: https://revealjs.com/
   #+END_SRC


*** URL form for file location

    For example if you cloned this repository to your home directory,
    this file in Mac OS X might be referred to as
    ~file:///Users/username/org-re-reveal/Readme.org~.  This file in
    GNU/Linux could be ~file:///home/username/org-re-reveal/Readme.org~,
    in Windows
    ~file:///c:/Users/username/org-re-reveal/Readme.org~.  For more
    details on this standard please refer to
    [[https://en.wikipedia.org/wiki/File_URI_scheme]].

** First Try

   The library org-re-reveal needs to be loaded first.  That can happen
   either by adding ~(require 'org-re-reveal)~ to your ~.emacs~ file or
   manually: Type "M-x load-library", then "org-re-reveal".

   Now you can export this manual, ~Readme.org~, into a reveal.js
   presentation by typing "C-c C-e v v".  That key binding can be
   changed by customizing ~org-re-reveal-keys~.

   Open the generated "Readme.html" in your browser and enjoy the
   cool slides.  (Of course, the location of reveal.js must be
   configured properly, as explained earlier.)

** Error about head.min.js
   Older versions of reveal.js included an initialization file
   ~head.min.js~, which does not exist with newer versions.  By
   default, ~org-re-reveal~ tries to load all files of
   ~org-re-reveal-script-files~.  If you see an error (in the
   browser’s console) that ~lib/js/head.min.js~ does not exist,
   customize ~org-re-reveal-script-files~ to remove it.

** The HLevel

   org-re-reveal maps each heading and its contents to one reveal.js
   slide. Since reveal.js arranges slides into a 2-dimensional matrix,
   org-re-reveal use a *HLevel* value to decide whether to map headings to horizontal
   or vertical slides.

   * Headings of level less than or equal to *HLevel* are mapped to horizontal
     slides.
   * Headings with a deeper level are mapped to vertical slides.

   HLevel's default value is 1, means only level 1 headings are arranged
   horizontally. Deeper headings are mapped to vertical slides below their
   parent level 1 heading.

*** HLevel's Effects on Slides Layout

    Assume we have a simple Org file as below:
#+BEGIN_SRC org
,* H1
,* H2
,** H2.1
,*** H2.1.1
,* H3
#+END_SRC

    If HLevel is 1, the default value, headings H2.1 and H2.1.1 will
    be mapped to vertical slides below the slides of heading H2.

    [[./images/hlevel.png]]

#+REVEAL: split

    If HLevel is changed to 2, slides of heading H2.1 will be changed
    to the main horizontal queue, and slides of heading H2.1.1 will be
    a vertical slide below it.

    [[./images/hlevel2.png]]

*** Configure HLevel's Value

    * Change variable =org-re-reveal-hlevel='s value to set HLevel globally.
      For example, add the following statement to your =.emacs= file.
      #+BEGIN_SRC lisp
(setq org-re-reveal-hlevel 2)
      #+END_SRC

    * Set HLevel within individual Org file with option =REVEAL_HLEVEL=:
      #+BEGIN_SRC org
,#+REVEAL_HLEVEL: 2
      #+END_SRC

** Subheadings

   If you want one slide to have its usual heading followed by a
   subheading, you can add a ~NOSLIDE~ property (and make sure that
   the subheading does not appear in the table of contents):
#+BEGIN_SRC org
,* A normal slide
,** A subheading
   :PROPERTIES:
   :UNNUMBERED: notoc
   :NOSLIDE: t
   :END:
#+END_SRC

** Force Split

   If one heading has too many things to fit into one slide, you can
   split the contents into multiple vertical slides manually, by inserting

#+BEGIN_SRC org
,#+REVEAL: split
#+END_SRC

#+REVEAL: split data-background="#555555"

   Now a new slide begins after the ~#+REVEAL~ keyword.

   By default, any background attributes of a slide should remain in
   effect for the split parts.  In addition, you can
   add HTML attributes after ~#+REVEAL: split~, e.g., this slide
   uses ~#+REVEAL: split data-background="#555555"~ to set a
   background color.

** Select Theme and Transition

    Themes and transition styles are set globally throughout the whole
    file by setting options =REVEAL_THEME=, =REVEAL_TRANS=, and =REVEAL_SPEED=.

    For an example, please check the heading part of this document.
    Note that some themes access remote servers to download fonts.
    Your privacy policy should explain this.

    Available themes can be found in "css/theme/" in the reveal.js
    directory and customized via ~org-re-reveal-theme~.

    Available transitions can be found in the
    [[https://github.com/hakimel/reveal.js/blob/master/README.md][README of reveal.js]]
    and customized via ~org-re-reveal-transition~.

** Set The Title Slide
   By default, org-re-reveal generates a title slide displaying the
   title, the author, the Email, the date and the time-stamp of the
   Org document, controlled by Org's [[https://orgmode.org/org.html#Export-settings][export settings]].

   To avoid a title slide, set variable
   ~org-re-reveal-title-slide~ to ~nil~ or add the following header line:
   ~#+REVEAL_TITLE_SLIDE:~

*** Customize the Title Slide

    To customize the title slide, set ~org-re-reveal-title-slide~
    to a string with HTML code.  Escape sequences are documented for
    variable ~org-re-reveal-title-slide~; they can be used to retrieve
    document information.  See
    [[https://gitlab.com/oer/org-re-reveal/blob/master/test-cases/test-title-slide.org][test-title-slide.org]]
    for an example including ~REVEAL_ACADEMIC_TITLE~,
    ~REVEAL_TALK_URL~, ~REVEAL_TALK_QR_CODE~

    Alternatively, you can also write the title slide's HTML code
    (with escape sequences) into a separate file and
    set ~org-re-reveal-title-slide~ to the name of that file.

** Set Slide Background

   Slide background can be set to a color, an image, or a repeating image
   array by setting heading properties.

   Keywords ~REVEAL_DEFAULT_SLIDE_BACKGROUND~, ~REVEAL_DEFAULT_SLIDE_BACKGROUND_POSITION~,
   ~REVEAL_DEFAULT_SLIDE_BACKGROUND_REPEAT~, ~REVEAL_DEFAULT_SLIDE_BACKGROUND_SIZE~, and
   ~REVEAL_DEFAULT_SLIDE_BACKGROUND_TRANSITION~ can be used to specify
   default values for options explained subsequently for individual
   slides.  Additional keywords ~REVEAL_TITLE_SLIDE_BACKGROUND~,
   ~REVEAL_TITLE_SLIDE_BACKGROUND_POSITION~,
   ~REVEAL_TITLE_SLIDE_BACKGROUND_REPEAT~,
   ~REVEAL_TITLE_SLIDE_BACKGROUND_SIZE~,
   ~REVEAL_TITLE_SLIDE_BACKGROUND_TRANSITION~ set those options for
   the title slide.

*** Colored Background
   :PROPERTIES:
   :reveal_background: linear-gradient(to left, #910830, #521623)
   :END:

    Set property =reveal_background= to either an RGB color value, or any
    supported CSS color format.

#+BEGIN_SRC org
,*** Colored Background
   :PROPERTIES:
   :reveal_background: linear-gradient(to left, #910830, #521623)
   :END:
#+END_SRC

*** Single Image Background - Instructions

    Set property =reveal_background= to an URL of background image.
    Set property =reveal_background_trans= to =slide= to make background image
    sliding rather than fading.
#+BEGIN_SRC org
,*** Single Image Background - Result
    :PROPERTIES:
    :reveal_background: ./images/adult-education-3258944_640.jpg
    :reveal_background_trans: slide
    :END:
#+END_SRC

*** Single Image Background - Result
    :PROPERTIES:
    :reveal_background: ./images/adult-education-3258944_640.jpg
    :reveal_background_trans: slide
    :END:

*** Repeating Image Background - Instructions

    Resize background image by setting property
    =reveal_background_size= to a number.

    Set property =reveal_background_repeat= to =repeat= to repeat
    image on the background.
#+BEGIN_SRC org
,*** Repeating Image Background - Result
    :PROPERTIES:
    :reveal_background: ./images/adult-education-3258944_640.jpg
    :reveal_background_size: 200px
    :reveal_background_repeat: repeat
    :END:
#+END_SRC

*** Repeating Image Background - Result
    :PROPERTIES:
    :reveal_background: ./images/adult-education-3258944_640.jpg
    :reveal_background_size: 200px
    :reveal_background_repeat: repeat
    :END:

*** Title Slide Background Image

    To set the title slide's background image, please specify the
    following options:

    * =REVEAL_TITLE_SLIDE_BACKGROUND=: A URL to the background image.
    * =REVEAL_TITLE_SLIDE_BACKGROUND_SIZE=: HTML size specification, e.g. ~200px~.
    * =REVEAL_TITLE_SLIDE_BACKGROUND_REPEAT=: set to ~repeat~ to repeat the image.

** Slide Size

   Reveal.js scales slides to best fit the display resolution, but you can
   also specify the desired size by settings the option tags =width= and =height=.

   The scaling behavior can also be constrained by setting following
   options:
   * =#+REVEAL_MARGIN:= :: a float number, the factor of empty area
        surrounding slide contents.
   * =#+REVEAL_MIN_SCALE:= :: a float number, the minimum scaling down
        ratio.
   * =#+REVEAL_MAX_SCALE:= :: a float number, the maximum scaling up
        ratio.

** Slide Numbering

   By default, the slide number is showed at the lower-right corner of each slide.

   To disable slide numbering, please add ~reveal_slide_number:nil~ to the
   ~#+OPTIONS:~ line.

   From reveal.js 3.1.0, slide numbering can have several custom
   formats. To choose one format, please set ~reveal_slide_number~ to
   its proper string. For example, ~reveal_slide_number:h/v~.

   Supported format strings can be found in the [[https://github.com/hakimel/reveal.js/#slide-number][reveal.js manual]].


** Slide Header/Footer
   Specify slide header/footer by =#+REVEAL_SLIDE_HEADER:= and
   =#+REVEAL_SLIDE_FOOTER:=. The option content will be put into
   divisions of class =slide-header= and =slide-footer=, so you can
   control their appearance in custom CSS file (see [[Extra Stylesheets]]).
   By default header/footer content will only display on content
   slides. To show them also on the title and toc slide you can add
   ~reveal_global_header:t~ and ~reveal_global_footer:t~ to
   ~#+OPTIONS:~ line. To show the footer on the toc slide but not on
   the title slide, use option ~reveal_toc_footer:t~.

** Fragmented Contents

    Make contents fragmented (show up one-by-one) by setting option
    =ATTR_REVEAL= with property ":frag frag-style", as illustrated
    below.

#+ATTR_REVEAL: :frag roll-in
    Paragraphs can be fragmented.

#+ATTR_REVEAL: :frag roll-in
    - Lists can
    - be fragmented.

#+ATTR_REVEAL: :frag roll-in
    Pictures, tables and many other HTML elements can be fragmented.

*** Fragment Styles
    Available fragment styles are:
#+ATTR_REVEAL: :frag t
    * grow
    * shrink
    * roll-in
    * fade-out
    * highlight-red
    * highlight-green
    * highlight-blue
    * appear

    Setting ~:frag t~ will use reveal.js default fragment style, which
    can be overridden by local option ~#+REVEAL_DEFAULT_FRAG_STYLE~ or
    global variable ~org-re-reveal-default-frag-style~.

*** Fragment Index
    Fragment sequence can be changed by assigning adding ~:frag_idx~
    property to each fragmented element.

#+ATTR_REVEAL: :frag t :frag_idx 3
    And, this paragraph shows at last.

#+ATTR_REVEAL: :frag t :frag_idx 2
    This paragraph shows secondly.

#+ATTR_REVEAL: :frag t :frag_idx 1
    This paragraph shows at first.

*** List Fragments

    ~#+ATTR_REVEAL: :frag frag-style~ above a list defines fragment
    style for the list as a whole.
#+ATTR_REVEAL: :frag grow
    1. All items grow.
    2. As a whole.

    To define fragment styles for every list item, please enumerate
    each item's style in a lisp list.

    ~none~ in the style list will disable fragment for the
    corresponding list item.

    Custom fragment sequence should also be enumerated for each list
    item.

#+REVEAL: split
    An example:

#+BEGIN_SRC org
,#+ATTR_REVEAL: :frag (grow shrink roll-in fade-out none) :frag_idx (4 3 2 1 -)
   * I will grow.
   * I will shrink.
   * I rolled in.
   * I will fade out.
   * I don't fragment.
#+END_SRC

#+ATTR_REVEAL: :frag (grow shrink roll-in fade-out none) :frag_idx (4 3 2 1 -)
   * I will grow.
   * I will shrink.
   * I rolled in.
   * I will fade out.
   * I don't fragment.
#+REVEAL: split
   When there is ~:frag_idx~ specified, insufficient fragment style
   list will be extended by its last element. So a ~:frag (appear)~
   assigns each item of a list the ~appear~ fragment style.
#+BEGIN_SRC org
,#+ATTR_REVEAL: :frag (appear)
   * I appear.
   * I appear.
   * I appear.
#+END_SRC
#+ATTR_REVEAL: :frag (appear)
   * I appear.
   * I appear.
   * I appear.

*** List Fragments with Audio

    You can also use org-re-reveal in combination with the
    audio-slideshow plugin of
    [[https://github.com/rajgoel/reveal.js-plugins][reveal.js-plugins]].
    For example, when the audio-slideshow plugin is configured
    properly, the following plays ~1.ogg~ when the first list item
    appears, ~2.ogg~ for the second list item, and no audio for the
    third.  (You need to add suitable audio files to the current
    directory first.)

#+BEGIN_SRC org
,#+ATTR_REVEAL: :frag (appear) :audio (1.ogg 2.ogg none)
   * I appear with audio 1.ogg.
   * I appear with audio 2.ogg.
   * I appear without audio.
#+END_SRC

#+ATTR_REVEAL: :frag (appear) :audio (1.ogg 2.ogg none)
   * I appear with audio 1.ogg.
   * I appear with audio 2.ogg.
   * I appear without audio.

** Data State and Classes for Headlines and Slides, including generated ones
   :PROPERTIES:
   :reveal_data_state: alert
   :END:

   Set property =reveal_data_state= to a headline to change this
   slide's display style.  (In the past, ~reveal.min.css~ defined
   classes ~alert~, ~blackout~, ~soothe~, which were activated by the
   data state.)  In any case, property =reveal_data_state= adds a
   ~data-state~ attribute to the slide's ~section~ element, which is
   called “Slide State” by reveal.js; this might also be useful with
   reveal.js plugins.

#+REVEAL: split
   To add a ~data-state~ attribute to a generated title slide or
   table of contents slide, you can use the following options:

   * =REVEAL_TITLE_SLIDE_STATE=
   * =REVEAL_TOC_SLIDE_STATE=

   To add a ~class~ attribute to a ~section~ element, use
   an [[*Extra Slide Attribute][Extra Slide Attribute]]
   (e.g., property ~:reveal_extra_attr: class="my-class"~).

   To add a ~class~ attribute to the ~section~ element of a generated
   table of contents slide, you can use the option
   =REVEAL_TOC_SLIDE_CLASS=.

   To add a ~class~ attribute to a slide's ~h~-element, add property
   =html_headline_class= to the headline.


** Third-Party Plugins
   Reveal.js is also extensible through third-party plugins, which can
   be loaded with org-re-reveal. Several plugins are included and
   configured with [[https://gitlab.com/oer/emacs-reveal][emacs-reveal]].

   The paths to javascript loading code
   need to be customized in the variable
   ~org-re-reveal-external-plugins~. This variable can be an
   associative list or a filename. If it is an associative list the first
   element of each Assoc cell is a symbol -- the name of the plugin --
   and the second is a string that will be expanded by the ~format~
   function when the plugin is loaded. So, this second element should
   have the form:

   ~" {src: \"%srelative/path/toplugin/from/reveal/root.js\"}"~

   If you need the async or callback parameters, include those too.

#+REVEAL: split

   If ~org-re-reveal-external-plugins~ is a filename, that file must
   contain strings of the above format, one per line (without names of
   plugins, just the ~src~ information embedded in braces); this can
   also be configured within your Org presentation with a line like
   this:

=#+REVEAL_EXTERNAL_PLUGINS: external_plugins.js=

   In any case, org-re-reveal will add the plugins to the dependencies
   parameter when Reveal is initialized.


** Highlight Source Code

   There are three options to highlight source code (or not), see doc
   string of customizable variable ~org-re-reveal-no-htmlize-src~.
   1. Use your Emacs theme with ~htmlize.el~
   2. Use highlight.js
   3. Disable htmlize with above variable, enable on selected source
      code blocks

   To use your Emacs theme, please make sure ~htmlize.el~ is
   installed. Then no more setup is necessary.

   If indentation is wrong, maybe set variable =org-html-indent=
   to =nil= and/or =org-src-preserve-indentation= to =t=.  Then export again.

*** Using highlight.js

    You can also use [[https://highlightjs.org][highlight.js]], by adding ~highlight~ to the reveal.js
    plugin list.
    #+BEGIN_SRC org
      ,#+REVEAL_PLUGINS: (highlight)
    #+END_SRC

    The default highlighting theme is ~zenburn.css~ brought with
    reveal.js. To use other themes, please specify the CSS file name by
    ~#+REVEAL_HIGHLIGHT_CSS~ or the variable ~org-re-reveal-highlight-css~.

    The "%r" in the given CSS file name will be replaced by reveal.js'
    URL.

#+MACRO: klipse-languages (eval (message "%s" (mapconcat #'identity org-re-reveal-klipse-languages ", ")))
** Editable and Executable Source Code
   Thanks to [[https://github.com/viebel/klipse][klipse]], it is
   possible to embed code blocks in CodeMirror instance in order to
   edit and execute code during a presentation.  Note that klipse
   support has been rewritten in org-re-reveal 1.1.11.  Previously,
   code was displayed in iframes, which does not allow to share state
   between different pieces of code; in particular, SQL did not work
   (see [[https://gitlab.com/oer/org-re-reveal/issues/23][this issue]]).

   Now, without iframes, some CSS settings of klipse and reveal.js are
   in conflict.  In particular, scaling needs to be disabled with
   klipse.  See settings of this Readme and examples in the Tips
   section under [[Executable Source Blocks]] as well as that
   [[https://gitlab.com/oer/org-re-reveal/blob/master/test-cases/test-klipsify.org][test file]]
   to get started.

   At present code editing is supported in: {{{klipse-languages}}}

** MathJax
  :PROPERTIES:
  :CUSTOM_ID: my-heading
  :END:

   ${n! \over k!(n-k)!} = {n \choose k}$

   LaTeX equations are rendered in native HTML5 contents.

   *IMPORTANT*: Displaying equations requires an internet connection
   to load JavaScript or a local MathJax installation.
   For the latter, set option =REVEAL_MATHJAX_URL= to
   the URL pointing to the local MathJax location.

   If you use MathJax from a remote location, your privacy policy
   should explain this.

** Preamble and Postamble

   You can define preamble and postamble contents which will not be
   shown as slides, but will be exported into the body part of the
   generated HTML file, at just before and after the slide contents.

   Change preamble and postamble contents globally by setting variable
   =org-re-reveal-preamble= and =org-re-reveal-postamble=.

   Change preamble and postamble contents locally by setting options
   =REVEAL_PREAMBLE= and =REVEAL_POSTAMBLE=, as illustrated at the
   heading part of this document.

   To add custom contents into HTML =<head>= parts, set contents to
   variable =org-re-reveal-head-preamble= or option
   =REVEAL_HEAD_PREAMBLE=.

*** Generating Pre/Postamble by Emacs-Lisp Functions

    If the contents of pre/postamble is the name of an evaluated
    Emacs-Lisp function, which must accept an argument of Org mode
    info and return a string, the returned string will be taken
    as pre/postamble contents.

    So you can embed the Emacs-Lisp function as an Org Babel source
    block and mark it to be evaluated when exporting the document.

** Raw HTML in Slides

   Besides the Org contents, you can embed raw HTML contents
   into slides by placing a =#+REVEAL_HTML= keyword.

   A talk by Linus Torvalds on Git (the source code to embed that
   video makes use of attribute ~data-src~ for lazy loading of the
   video):
   #+REVEAL_HTML: <video controls width="400" height="300" data-src="https://archive.org/download/LinusTorvaldsOnGittechTalk/LinusTorvaldsOnGittechTalk.ogv"></video>

** Speaker Notes
   Reveal.js supports speaker notes, which are displayed in a separate
   browser window. Pressing 's' on slide's windows opens a popup
   window (or indicates if you need to enable this browser feature)
   displaying the current slide with its speaker notes, a timer, and a preview
   of upcoming contents.  To configure timing, see
   ~org-re-reveal-defaulttiming~.
   The following example shows how to define speaker notes for a slide
   with an estimated talk time of 120s.

#+BEGIN_SRC org
,* Heading 1
   :PROPERTIES:
   :reveal_extra_attr: data-timing="120"
   :END:
   Some contents.
,#+BEGIN_NOTES
  Enter speaker notes here.
  - With bullet points
    - If necessary
,#+END_NOTES
#+END_SRC

#+REVEAL: split
   Speaker note functionality requires that ~notes~ is configured as
   plugin (which is true by default with ~org-re-reveal-plugins~) and
   that popup windows are permitted.

   Due to a bug in reveal.js, sometimes the speaker notes window does
   not initialize properly.  As workaround, close the speaker notes
   windows and press ’s’ again; notes should be working then.
   If this does not work, you may need to put the presentation HTML
   file into the reveal.js root directory and reopen it in the browser.

*** Easy-Template for Speaker Notes

    Org-re-reveal registers 'n' as key for the speaker notes template:
    You can press '<' followed by 'n' and then press TAB, which
    inserts ~#+begin_notes~ and ~#+end_notes~.  For this to work with
    Org version 9.2 or newer, you need to place ~(require 'org-tempo)~
    into your ~.emacs~ or add ~org-tempo~ to ~org-modules~.  (Besides,
    function ~org-insert-structure-template~ allows to insert different
    kinds of block structures.)

    Customize ~org-re-reveal-note-key-char~ to change the default key
    'n'.  Set to nil to avoid auto-completion for speaker notes.

** Multiplexing
   Reveal.js supports multiplexing, which allows allows your audience to view
   the slides of the presentation you are controlling on their own phone, tablet
   or laptop. As the master presentation navigates the slides, all client
   presentations will update in real time.

   Please see
   [[https://gitlab.com/oer/org-re-reveal/blob/master/test-cases/test-multiplex.org][this sample presentation for instructions]].
   Briefly, you need to configure ~multiplex~ as plugin, with
   URL, ID and Secret of a socket.io server.  Then, generate master
   (with Secret) and client presentations and publish the client
   presentation for your audience.

** Extra Stylesheets

   Set =REVEAL_EXTRA_CSS= to a stylesheet file path in order to load extra custom
   styles after loading a theme.

#+BEGIN_SRC org
,#+REVEAL_EXTRA_CSS: url-to-custom-stylesheet.css
#+END_SRC

** Select Built-In Scripts

   Set option =REVEAL_PLUGINS= or variable =org-re-reveal-plugins= to a
   lisp list to activate additional reveal.js functionality.

   Variable =org-re-reveal-plugins= allows to select among available plugins.

   The following example selects /markdown/, /highlight/, and /search/.
#+BEGIN_SRC org
,#+REVEAL_PLUGINS: (markdown highlight search)
#+END_SRC

** Extra JavaScript Libraries

   Set =REVEAL_EXTRA_SCRIPTS= to a list of extra JavaScript
   libraries of script elements.
#+BEGIN_SRC org
,#+REVEAL_EXTRA_SCRIPTS: ("filename.js" "<script>Your code here\n</script>")
#+END_SRC

** Extra Slide Attribute

   Set =REVEAL_EXTRA_ATTR= to add any additional attributes to all slides if
   required.
#+BEGIN_SRC org
,#+REVEAL_EXTRA_ATTR: data-autoslide=20000
#+END_SRC

   This global default value can also be overridden per heading by setting
   =reveal_extra_attr= property on the headings.
#+BEGIN_SRC org
,*** Heading with overriden autoslide
   :PROPERTIES:
   :reveal_extra_attr: data-autoslide=10000
   :END:
#+END_SRC

** Export into Single File

   By setting option =reveal_single_file= to ~t~, images and basic
   reveal.js scripts will be embedded into the exported HTML file, to make
   a portable HTML. Please note that remote images will /not/ be included in the
   single file, so presentations with remote images will still require an Internet
   connection.

   Attention: This needs locally available reveal.js files!

   #+BEGIN_SRC org
   ,#+OPTIONS: reveal_single_file:t
   #+END_SRC

#+REVEAL: split

   *Limitations* of single file export
   * Some functions provided by reveal.js libraries will be
     *disabled*, including PDF export, Markdown support, zooming,
     speaker notes, and remote control.
     * Code highlighting by highlight.js is also disabled, but *code
       highlighting by Emacs is not affected.*
   * Plugins are *not* enabled.
   * CSS needs to be *self-contained*.  Neither ~@import~ rules nor
     other forms of URLs work (images need to be embedded as
     data URIs).
   * If you use ~org-re-reveal-title-slide~ with custom HTML code and
     images, you need to embed images in the form of data URIs
     yourself.


** Export Current Subtree

  Use menu entry "C-c C-e v s" to export only current subtree,
  without the title slide and the table of content, for a quick preview
  of your current edition.

  Customize ~org-re-reveal-subtree-with-title-slide~ to also export a
  title slide.

* Tips

** En-/Disable Heading Numbers

   Use Org export option =num=, e.g., =num:t= or =num:nil=:
#+BEGIN_SRC org
,#+OPTIONS: num:nil
#+END_SRC

   With heading numbers (i.e., without ~num:nil~), depending on
   ~org-re-reveal-generate-custom-ids~, (more) stable slide IDs can be
   generated (instead of hash values that change with content
   changes).  See doc string (~C-h v~) of variable
   ~org-re-reveal-generate-custom-ids~ for more details.

** Disable Table of Contents

   Add =toc:nil= to =#+OPTIONS= to disable the table of contents:
#+BEGIN_SRC org
,#+OPTIONS: toc:nil
#+END_SRC

   This is actually an option recognized by =org-export=.

** Table of Contents at Specified Position
   When using option =toc:nil=, you can also insert a slide with the table
   of contents at a position of your choice with keyword =REVEAL_TOC=
   (where the number after =headlines= defines the depth of headlines
   to include) in a section of its own (see this
   [[https://gitlab.com/oer/org-re-reveal/blob/master/test-cases/test-slide-numbers-reveal-toc.org][test file]]):

#+BEGIN_SRC org
,** Table of Contents
   :PROPERTIES:
   :UNNUMBERED: notoc
   :END:
,#+REVEAL_TOC: headlines 1
#+END_SRC

*WARNING:* Previous versions of org-re-reveal used keyword =TOC= (which
generates the table of contents in a section with default headline)
instead of =REVEAL_TOC=.  Keyword =TOC= may or may not work for you.
Its use is discouraged as it may break some presentations.

** Internal Links

   Reveal.js only supports jumps to entire slides, but not to specific
   elements on slides. Thus, we can only link to headlines in an Org
   document.

   You can create links pointing to a headline's text, or its
   custom-id, as in the examples below:

   * [[Tips]].
   * [[#my-heading][Heading]] with a =CUSTOM_ID= property.

#+REVEAL: split
   If you add =reveal_inter_presentation_links:t= to =#+OPTIONS=, such
   links also work between presentations on the same server, e.g.,
   =[[file:somefile.org::#anchor][link text]]=.

   Reveal.js [[https://github.com/hakimel/reveal.js#internal-links][advertises]]
   to use broken internal links, which are used in org-re-reveal by
   default.  (Those links work with reveal.js, but are not understood
   by search engines.)  If you change ~org-re-reveal--href-fragment-prefix~
   from its default to the value of ~org-re-reveal--slide-id-prefix~,
   valid links are generated:
   #+BEGIN_SRC lisp
   (setq org-re-reveal--href-fragment-prefix org-re-reveal--slide-id-prefix)
   #+END_SRC
   Whether this change is a good idea might be discussed under this
   [[https://github.com/hakimel/reveal.js/issues/2276][reveal.js issue]].

** Custom JS

   To pass custom JS code to ~Reveal.initialize~, state the code by
   ~#+REVEAL_INIT_SCRIPT~ (multiple statements are concatenated) or by
   custom variable ~org-re-reveal-init-script~.

** Executable Source Blocks
   To allow live execution of code in some languages, enable the
   klipse plugin
   with variable ~org-re-reveal-klipsify-src~ (or with option ~reveal_klipsify_src:t~)

   Src blocks with the languages contained in
   ~org-re-reveal-klipse-setup~ will be executed with output shown in
   a console-like environment.  See
   [[https://github.com/viebel/klipse#klipse][the README of klipse]]
   for more details.

   Additional examples (e.g., Python and SQL) can be found in a
   [[https://gitlab.com/oer/org-re-reveal/blob/master/test-cases/test-klipsify.org][test file]].

*** HTML Src Block
#+BEGIN_SRC html
<h1 class="whatever">hello, what's your name</h1>
#+END_SRC

*** Javascript Src Block
#+BEGIN_SRC js
console.log("success");
var x='string using single quote';
x
#+END_SRC

*** Perl Src Block (not klipsified)
#+BEGIN_SRC perl
I don't know perl!
#+END_SRC
* Thanks

  Courtesy to:

#+ATTR_REVEAL: :frag roll-in
  The powerful Org mode,
#+ATTR_REVEAL: :frag roll-in
  the impressive reveal.js
#+ATTR_REVEAL: :frag roll-in
  and the precise MathJax