Add RTL support to Discourse CSS pre-processing using the RTLit gem and configurable via discourse.conf

Gemfile

@@ -154,6 +154,7 @@ gem 'rack-protection' # security
 group :assets do
   gem 'sass-rails', '~> 4.0.2'
   gem 'uglifier'
+  gem 'rtlit' # for css rtling
 end
 
 group :test do

Gemfile.lock

@@ -308,6 +308,7 @@ GEM
       rspec-core (~> 2.14.0)
       rspec-expectations (~> 2.14.0)
       rspec-mocks (~> 2.14.0)
+    rtlit (0.0.5)
     ruby-openid (2.5.0)
     ruby-readability (0.6.1)
       guess_html_encoding (>= 0.0.4)
@@ -464,6 +465,7 @@ DEPENDENCIES
   rmmseg-cpp
   rspec-given
   rspec-rails
+  rtlit
   ruby-readability
   sanitize
   sass

config/discourse_defaults.conf

@@ -97,3 +97,6 @@ serve_static_assets = false
 
 # number of sidekiq workers (launched via unicorn master)
 sidekiq_workers = 5
+
+# adjust stylesheets to rtl (requires "rtlit" gem)
+rtl_css = false

lib/sass/discourse_sass_compiler.rb

@@ -49,7 +49,7 @@ class DiscourseSassCompiler
       style: :expanded
     }
 
-    ::Sass::Engine.new(@scss, {
+    css = ::Sass::Engine.new(@scss, {
       syntax: :scss,
       cache: false,
       read_cache: false,
@@ -60,6 +60,14 @@ class DiscourseSassCompiler
         environment: context.environment
       }
     }.merge(debug_opts)).render
+
+    # Check if CSS needs to be RTLed after compilation
+    # and run RTLit gem on compiled CSS if true and RTLit gem is available
+    if GlobalSetting.rtl_css && defined?(RTLit)
+      RTLit::Converter.to_rtl(css)
+    else
+      css
+    end
   end
 
 end