Add support for org-reveal to org layer

org-reveal is an extension to org mode that allows exporting of org files as
reveal.js presentations. Since not everyone needs this functionality, the
loading of the package is controlled via the `org-enable-reveal-js` switch,
which, if set to `t` would load the package.

layers/+emacs/org/README.org

@@ -11,6 +11,7 @@
    - [[#layer][Layer]]
    - [[#github-support][Github support]]
    - [[#gnuplot-support][Gnuplot support]]
+   - [[#reveal.js support][reveal.js support]]
    - [[#different-bullets][Different bullets]]
  - [[#key-bindings][Key bindings]]
    - [[#org][Org]]
@@ -88,6 +89,26 @@ at this stage.  It is possible to disable the configuration of gnuplot support
 as usual by adding the package =gnuplot= to your =dotspacemacs-excluded-packages=
 variable.
 
+** Reveal.js support
+
+To enable the export of your org file as a [[http://lab.hakim.se/reveal-js/][reveal.js]] presentation, set the
+variable =org-enable-reveal-js= to =t=. This will install the [[https://github.com/yjwen/org-reveal/][org-reveal]] extension.
+
+#+BEGIN_SRC emacs-lisp
+  (setq-default dotspacemacs-configuration-layers '(
+    (org :variables
+         org-enable-reveal-js t)))
+#+END_SRC
+
+In order to be able to use org-reveal, download =reveal.js= from its
+[[http://lab.hakim.se/reveal-js/#/][homepage]] and set =org-reveal-js= to the
+download path, as described in the [[https://github.com/yjwen/org-reveal#obtain-revealjs][manual]]. Alternatively, add the following line
+to each =.org= file you want to process:
+
+#+BEGIN_EXAMPLE
+#+REVEAL_ROOT: http://cdn.jsdelivr.net/reveal.js/3.0.0/
+#+END_EXAMPLE
+
 ** Different bullets
 You can tweak the bullets displayed in the org buffer in the function
 =dotspacemacs/user-config= of your dotfile by setting the variable

layers/+emacs/org/config.el

@@ -14,4 +14,7 @@
 (defvar org-enable-github-support nil
   "If non-nil Github related packages are configured.")
 
+(defvar org-enable-reveal-js nil
+  "If non-nil, enables ox-reveal export.")
+
 (spacemacs|defvar-company-backends org-mode)

layers/+emacs/org/packages.el

@@ -31,6 +31,7 @@
     org-repo-todo
     (ox-gfm :location local)
     persp-mode
+    ox-reveal
     ))
 
 (defun org/post-init-company ()
@@ -559,6 +560,24 @@ a Markdown buffer and use this command to convert it.
     :body
     (find-file (first (org-agenda-files)))))
 
+(defun org/init-toc-org ()
+  (use-package toc-org
+    :defer t
+    :init
+    (progn
+      (setq toc-org-max-depth 10)
+      (add-hook 'org-mode-hook 'toc-org-enable))))
+
+(defun org/init-ox-reveal ()
+  (use-package ox-reveal
+    :if org-enable-reveal-js
+    :defer t
+    :init
+    (progn
+      ;; seems to be required otherwise the extension is not
+      ;; loaded properly by org
+      (with-eval-after-load 'org (require 'ox-reveal)))))
+
 (defun org/init-htmlize ()
  (use-package htmlize
    :defer t))