Module AssetHat::CSS

Given a string containing CSS, appends each referenced asset’s last commit ID to its URL, e.g., background: url(/images/foo.png?ab12cd3). This enables cache busting: If the user’s browser has cached a copy of foo.png from a previous deployment, this new URL forces the browser to ignore that cache and request the latest version.

    # File lib/asset_hat/css.rb, line 43
43:     def self.add_asset_commit_ids(css)
44:       update_css_urls(css, %w[images htc]) do |src, quote|
45:         # Get absolute path
46:         filepath = File.join(ASSETS_DIR, src)
47: 
48:         # Convert to relative path
49:         filepath.sub!(/^#{FileUtils.pwd}#{File::SEPARATOR}/, '')
50: 
51:         commit_id = AssetHat.last_commit_id(filepath)
52:         if commit_id.present?
53:           "url(#{quote}#{src}#{src =~ /\?/ ? '&' : '?'}#{commit_id}#{quote})"
54:         else
55:           "url(#{quote}#{src}#{quote})"
56:         end
57:       end
58:     end

Arguments:

• A string containing CSS;
• A string containing the app’s asset host, e.g., ‘http://cdn%d.example.com’. This value is typically taken from config.action_controller.asset_host in the app’s config/environments/production.rb.

An asset host is added to every image URL in the CSS, e.g., background: url(http://cdn2.example.com/images/foo.png); if %d in the asset host, it is replaced with an arbitrary number in 0-3, inclusive.

Options:

ssl

Set to true to simulate a request via SSL. Defaults to false.

    # File lib/asset_hat/css.rb, line 77
77:     def self.add_asset_hosts(css, asset_host, options={})
78:       return css if asset_host.blank?
79: 
80:       options.reverse_merge!(:ssl => false)
81: 
82:       update_css_urls(css, %w[images]) do |src, quote|
83:         computed_asset_host = AssetHat.compute_asset_host(
84:           asset_host, src, options.slice(:ssl))
85:         "url(#{quote}#{computed_asset_host}#{src}#{quote})"
86:       end
87:     end

Returns the expected path for the minified version of a CSS asset:

AssetHat::CSS.min_filepath('public/stylesheets/bundles/application.css')
  # => 'public/stylesheets/bundles/application.min.css'

    # File lib/asset_hat/css.rb, line 14
14:     def self.min_filepath(filepath)
15:       AssetHat.min_filepath(filepath, 'css')
16:     end

Accepts a string of CSS, and returns that CSS minified. Options:

engine

Default is :cssmin; see Engines.cssmin. Allowed values are in ENGINES.

    # File lib/asset_hat/css.rb, line 23
23:     def self.minify(input_string, options={})
24:       options.reverse_merge!(:engine => :cssmin)
25: 
26:       engine = options[:engine].to_sym
27:       unless ENGINES.include?(engine)
28:         raise %{
29:           Unknown CSS minification engine '#{engine}'.
30:           Allowed: #{ENGINES.map{ |e| "'#{e}'" }.join(', ')}
31:         }.strip.gsub(/\s+/, ' ') and return
32:       end
33: 
34:       AssetHat::CSS::Engines.send(engine, input_string).strip
35:     end