Rack Middleware for code highlighting.
The Rack::Codehighlighter is a middleware which allows for easy
connecting a code highlighter of somebody’s choice to an HTML page
containing pieces of programming code. Parameters to
Rack::Codehighlighter are: the name of a highlighter and a
specification of how to find the pieces of code in the page.
It supports the most popular Ruby code highlighters of today:
As well as
To ease testing it implements censor highlighter.
Rack::Codehighlighter looks for code blocks to be highlighted in the HTML
produced by your application. For each block found it calls requested
highlighter.
Install the gem with:
gem install rack-codehighlighter
In order for the highlighting to show up, you’ll need to include a
highlighting stylesheet. For example stylesheets you can look at
stylesheets in the examples/public/stylesheets directory.
In order to use, include the following code in a Rails application
config/environment.rb file:
require 'coderay' # get one of supported highlighters
require 'rack/codehighlighter'
Rails::Initializer.run do |config|
config.gem 'coderay'
config.gem 'rack-codehighlighter'
config.middleware.use Rack::Codehighlighter, :coderay, :element => "pre", :pattern => /\A:::(\w+)\s*\n/
end
In order to use, update Gemfile with:
gem 'coderay'
gem 'rack-codehighlighter', :require => 'rack/codehighlighter'
Next, add Rack::Codehighlighter to the application middleware stack,
updating config/environments/development.rb and
config/environments/production.rb with:
config.middleware.use Rack::Codehighlighter, :coderay,
:element => "pre", :pattern => /\A:::(\w+)\s*(\n|
)/i, :logging => false
(see Rails on Rack).
The rack-codehighlighter gem can be used with any Rack application,
for example with a Sinatra application. If your application
includes a rackup file or uses Rack::Builder to construct the
application pipeline, simply require and use as follows:
require 'coderay' # get one of supported highlighters
require 'rack/codehighlighter'
use Rack::Codehighlighter, :coderay, :element => "pre", :pattern => /\A:::(\w+)\s*\n/
run app
To colorize code in pre elements with well known coderay
highlighter use the following:
use Rack::Codehighlighter, :coderay, :element => "pre", :pattern => /\A:::(\w+)\s*\n/
The first parenthesized expression from the pattern /\A:::(\w+)\s*\n/
will be used to match the language name. For example, from the pre
element below:
<pre>:::ruby
puts "hello world"
</pre>
the ruby name is extracted.
To find the appropriate name to use for programming language,
look at the lists below.
Next, the matched element is removed and the second line is passed to
coderay highlighter for processing.
The highlighted code returned by the coderay highlighter is
wrapped with pre element with attributes appropriate for the
codehighlighter used.
In examples displayed below, the default value of each option is used.
Coderay:
use Rack::Codehighlighter, :coderay,
:element => "pre", :pattern => /\A:::(\w+)\s*(\n|
)/i, :logging => false
Ultraviolet:
use Rack::Codehighlighter, :ultraviolet, :theme => "dawn", :lines => false,
:element => "pre", :pattern => /\A:::(\w+)\s*(\n|
)/i, :logging => false
or
use Rack::Codehighlighter, :ultraviolet, :markdown => true,
:theme => "minimal_theme", :lines => false, :element => "pre>code",
:pattern => /\A:::([-_+\w]+)\s*(\n|
)/, :logging => false,
:themes => {"vibrant_ink" => ["ruby"], "upstream_sunburst" => ["objective-c", "java"]}
Unofficial Pygments API (uses web service, no dependencies):
use Rack::Codehighlighter, :pygments_api, :element => "pre",
:pattern => /\A:::([-_+\w]+)\s*(\n|
)/, :logging => false
Rygments (with the rygments gem):
use Rack::Codehighlighter, :rygments, :element => "pre",
:pattern => /\A:::([-_+\w]+)\s*(\n|
)/, :logging => false
Pygments (with the pygments.rb gem):
use Rack::Codehighlighter, :pygments, :element => "pre>code",
pattern => /\A:::([-_+\w]+)\s*(\n|
)/, :logging => false,
options => { :linenos => 'inline' }
(the options hash can accept standard Pygments configuration options).
Syntax:
use Rack::Codehighlighter, :syntax,
:element => "pre", :pattern => /\A:::(\w+)\s*(\n|
)/i, :logging => false
Censor:
use Rack::Codehighlighter, :censor, :reason => "[[-- ugly code removed --]]",
:element => "pre", :pattern => /\A:::(\w+)\s*(\n|
)/i, :logging => false
Markdown, Maruku and RDiscount processors, the code is wrapped with pre>code.
To remove this extra one level of nesting the :markdown option should be used:
use Rack::Codehighlighter, :coderay, :markdown => true,
:element => "pre>code", :pattern => /\A:::(\w+)\s*(\n|
)/i, :logging => false
Remark: Within pre tag, HAML replaces each new line characters
with the 
 entity (line feed) so that it can ensure that it
doesn’t adversely affect indentation.
This change confuses both rack-codehighlighter and the highlighters
themselves (e.g. Ultraviolet and Coderay). So, to support pre tags
as rendered by HAML, 
 was added to the default pattern.
The examples directory contains several rackup files.
Each rackup file uses a different highlighter.
Try, for example, the Pygments highlighter:
rackup coderay.ru
The results could be checked at http://localhost:9292.
A simple Copy & Paste example.
# example.rb
require 'rubygems'
require 'sinatra'
require 'rack/codehighlighter'
use Rack::Codehighlighter, :censor, :reason => '[[--difficult code removed--]]'
get "/" do
erb :hello
end
__END__
@@ hello
<h3>Fibonacci numbers in Ruby</h3>
<pre>:::ruby
def fib(n)
if n < 2
1
else
fib(n-2) + fib(n-1)
end
end
</pre>
Run the example with:
ruby example.rb
and check the results at http://localhost:4567.
These currently include: Syntax (fast), Coderay (very fast),
Ultraviolet (slow, but highlights almost any language),
Pygments (via the rygments gem or unofficial api).
Languages supported by Syntax:
Languages supported by
the coderay library:
The ultraviolet gem needs oniguruma regexp library.
On Fedora install the library with:
sudo yum install oniguruma oniguruma-devel
For installation instruction of the oniguruma library from sources,
see Carbonica
Now, install the gem:
sudo gem install ultraviolet
Install a fixed version of the Ultraviolet syntax highlighting
library for the 1.9 tree of the Ruby programming language from
here.
See also Ultraviolet themes gallery
Ultraviolet supports almost any language: