compass_initializer.rb

# Compass configuration from inside a rails3 engine

require 'compass' 
require 'compass/app_integration/rails' 

configuration = StringIO.new(<<-CONFIG) 
  project_type = :rails 
  css_dir = "public/stylesheets"
  sass_dir = "app/stylesheets" 
CONFIG

Compass.reset_configuration!
Compass.add_configuration(configuration, __FILE__)
Compass.configuration.project_path = Rails.root.to_s
Compass.discover_extensions! 
Compass.configure_sass_plugin! 

if Rails.env.development?
  Compass.configuration.on_stylesheet_saved {|filepath| Rails.logger.debug("Compass saved #{filepath}") }
  Compass.configuration.on_stylesheet_error {|filepath, message| Rails.logger.error("Compass has error in #{filepath}: #{message}") }
end

Compass.handle_configuration_change!

engine_initializer.rb

# Separately, this is how the engine adds its sass templates to the
# `surrounding` Rails.application

  class Engine < Rails::Engine
  
    initializer "Add to Sass load path", :after=>"compass.initialize_rails" do
      # root is initialized elsewhere and contains a PathName pointing to the engine's root directory
      Sass::Plugin.add_template_location(root.join('app', 'stylesheets'), Rails.root.join('public', 'stylesheets', 'engine'))
    end
    
  end