Version: 1.1.alpha.0

Sass-based Configuration Options

Most of the options available in the Ruby-based configuration file are used to configure the Sass compiler. These options cannot be configured from within your Sass files.

However some Compass options are possible to set from within Sass because they are only used to control how Compass's built-in functions work. For example, url generation using image-url() and font-url().

The options that can be set via Sass configuration are:

  • asset-cache-buster - String, Function reference, or null. The function reference must accept two arguments (url path, filename) and can return either a string to be interpreted as a query parameter or a map containing the keys query and/or path mapped to a string. The string is a simple value to set as the query parameter on all urls, when null, the cache busting feature is disabled.
  • asset-collections - List of Maps. Each map is a set of keys that describe an asset collection. The keys are basically the same as for the ruby configuration of asset collections with the following exceptions: 1. keys can be dashed instead of underscored. 2. Procs should be function references as described here for asset-cache-buster and asset-host. 3. The sass-dir option doesn't work because it must be set up external to the sass file itself.
  • asset-host - Function reference, or null. When null this feature is disabled (default). A referenced function must accept a single argument (the root relative url) and return a full url (starting with "http").
  • disable-warnings - Boolean. When true, warnings will not be output.
  • fonts-dir - String. Relative to project directory.
  • fonts-path - String. Absolute path.
  • generated-images-dir - String. Relative to project directory.
  • generated-images-path - String. Absolute path.
  • http-fonts-dir - String. Relative to project directory.
  • http-fonts-path - String. Absolute path.
  • http-generated-images-dir - String. Relative to http path.
  • http-generated-images-path - String. Absolute path.
  • http-images-dir - String. Relative to project directory.
  • http-images-path - String. Absolute path.
  • http-path - String. URL Prefix of all urls starting with '/'.
  • images-dir - String. Relative to project directory.
  • images-path - String. Absolute path.
  • relative-assets - Boolean. When true, generate relative paths from the css file to the asset.

The have the same meaning as the corresponding options in the ruby configuration format. However, there are some things that are different that are worth explaining.

Working with paths.

Compass provides a function called absolute-path that will turn any path relative to the sass file it is called from into an absolute path. In order to make your stylesheets work on both windows and unix-based operating systems, you should use the join-file-segments function instead of a file separator.

For example. If your configuration partial was stored in a subdirectory of your sass folder you would want to set $project-path to absolute-path(join-file-segments('..', '..')).

In some cases it is useful to parse a url or filename. The function split-filename($filename) returns a triple of (directory, basename, extension).

Working with Function References

Some configuration options passed to compass accept a function reference. This is an identifier that is the same name as a Sass function defined in either Sass or Ruby. What arguments the function accepts and should return depends on the particular configuration property. For example:

@function my-cache-buster($url, $file) {
  $hash: md5sum($file);
  @if $hash {
    @return (query: "h=#{$hash}");
  } @else {
    @return null;

@include compass-configuration($asset-cache-buster: my-cache-buster);

Configuration File Best Practices

It is suggested that all compass configuration performed from within Sass should be kept in a single partial named project-setup. This file should be imported into every Sass file that is to be used with Compass.

Understanding the project setup file

$project-path: absolute-path("..");

The global $project-path must be set to an absolute path to the directory of the project. This global is used to initial compass when importing compass/configuration.

$debug-configuration: true;

Causes compass to output useful debugging information about how it is configured.

@import "compass/configuration";

Initializes compass and makes some useful configuration utilities available.

    $compass-options: (http_path: "/");
    @include compass-configuration($compass-options);

Configures Compass according to your specific needs. If this mixin is called more than once it will give you a warning. To reconfigure compass with different options, pass $reconfigure: true to the compass-configuration mixin.