Making markdown engine configurable per slideshow

* allows to configure the markdown engine in the showoff.json
* allows to use math mode for slides if applicable
* documentation on how to use other markdown engines

README.rdoc

@@ -447,6 +447,42 @@ You'll then need to install a version of wkhtmltopdf available at the {wkhtmltop
 
 Then restart showoff, and navigate to <tt>/pdf</tt> (e.g. http://localhost/pdf) of your presentation and a PDF will be generated with the browser.
 
+= Misc
+
+== Markdown Engine
+
+It is possible to configure the markdown engine of your choice to use
+with showoff. This allows you to use special features of the different
+engines.
+
+=== Maruku
+
+When you prefer using Maruku as the markdown engine of choice for your
+presentation, you can use the Latex Math Mode features of
+maruku. First you need
+{BlahTex}[http://www.mediawiki.org/wiki/Extension:Blahtex] and then
+you need to configure your presentation as following:
+
+    { /* other config */,
+     "markdown" : "maruku",
+     "maruku" : {
+     	      "use_tex" : true,
+	      "png_dir" : "images", /*optional*/
+	      "html_png_url" : "/file/images/" /*optional*/
+       }
+     }
+
+
+=== Other Engines
+
+The following engines are preconfigured
+
+* redcarpet (default)
+* bluecloth
+* maruku
+* rdiscount
+
+
 = Completion
 
 == ZSH completion

lib/showoff.rb

@@ -58,6 +58,9 @@ def initialize(app=nil)
 
     # Default asset path
     @asset_path = "./"
+
+    # Initialize Markdown Configuration
+    MarkdownConfig::setup( settings.pres_dir )
   end
 
   def self.pres_dir_current

lib/showoff_utils.rb

@@ -282,13 +282,17 @@ def self.showoff_pdf_options(dir = '.')
     Hash[opts.map {|k, v| [k.to_sym, v]}] # keys must be symbols
   end
 
+  def self.showoff_markdown(dir = ".")
+    get_config_option(dir, "markdown", "redcarpet")
+  end
+
   def self.get_config_option(dir, option, default = nil)
     index = File.join(dir, ShowOffUtils.presentation_config_file)
     if File.exists?(index)
       data = JSON.parse(File.read(index))
       if data.is_a?(Hash)
         if default.is_a?(Hash)
-          default.merge(data[option])
+          default.merge(data[option] || {})
         else
           data[option] || default
         end
@@ -358,3 +362,45 @@ def self.create_file_if_needed(filename,force)
     end
   end
 end
+
+# Load the configuration for the markdown engine form the showoff.json
+# file
+module MarkdownConfig
+
+  def self.setup( dir_name )
+
+    # Load markdown configuration
+    case ShowOffUtils.showoff_markdown(dir_name)
+    when 'rdiscount'
+      Tilt.prefer Tilt::RDiscountTemplate, "markdown"
+    when 'maruku'
+
+      Tilt.prefer Tilt::MarukuTemplate, "markdown"
+      # Now check if we can go for latex mode
+      require 'maruku'
+      require 'maruku/ext/math'
+
+      # Load maruku options
+      opts = ShowOffUtils.get_config_option(dir_name, 'maruku',
+                                            {'use_tex' => false,
+                                              'png_dir' => 'images',
+                                              'html_png_url' => '/file/images/'})
+
+      if opts['use_tex']
+
+        MaRuKu::Globals[:html_math_output_mathml] = false
+        MaRuKu::Globals[:html_math_engine] = 'none'
+
+        MaRuKu::Globals[:html_math_output_png] = true
+        MaRuKu::Globals[:html_png_engine] =  'blahtex'
+        MaRuKu::Globals[:html_png_dir] = opts['png_dir']
+        MaRuKu::Globals[:html_png_url] = opts['html_png_url']
+      end
+
+    when 'bluecloth'
+      Tilt.prefer Tilt::BlueClothTemplate, "markdown"
+    else
+      Tilt.prefer Tilt::RedcarpetTemplate, "markdown"
+    end
+  end
+end

test/fixtures/maruku/one/01_slide.md

@@ -0,0 +1,16 @@
+!SLIDE 
+# My Presentation #
+
+!SLIDE bullets incremental
+# Bullet Points #
+
+* first point
+* second point
+* third point
+
+
+!SLIDE 
+
+# Math Mode #
+
+$\forall x \in X; \sum_i=x^i$

test/fixtures/maruku/showoff.json

@@ -0,0 +1,7 @@
+{ "name": "My Preso", 
+  "sections": [ {"section":"one"} ],
+  "markdown" : "maruku",
+  "maruku" : {
+      "use_tex" : true
+  }
+}

test/markdown_test.rb

@@ -0,0 +1,43 @@
+require File.expand_path "../test_helper", __FILE__
+
+begin
+  require 'maruku'
+  do_maruku = true
+rescue LoadError
+  do_maruku = false
+end
+
+context "ShowOff Maruku tests" do
+
+  def app
+    opt = {:verbose => false, :pres_dir => "test/fixtures/maruku", :pres_file => 'showoff.json'}
+    ShowOff.set opt
+    ShowOff.new
+  end
+
+  setup do
+  end
+
+  test "maruku can get the index page" do
+    get '/'
+    assert last_response.ok?
+    assert_match '<div id="preso">', last_response.body
+  end
+
+  test "maruku can get basic slides" do
+    get '/slides'
+    assert last_response.ok?
+    assert_match /<h1(.*?)>My Presentation<\/h1>/, last_response.body
+  end
+
+  test "maruku transforms equation to math mode" do
+    get '/slides'
+    assert_match /<span class="maruku-inline"><img alt="\$\\forall/, last_response.body
+  end
+
+  test "maruku can math mode" do
+    assert_equal "maruku", ShowOffUtils.showoff_markdown("test/fixtures/maruku")
+  end
+
+
+end if do_maruku