by Brandon Rhodes • Home

Adding Compass to your project

Date: 13 May 2011
Tags:computing

The Compass CSS authoring framework has become one of the standard tools that gets installed when I start working on a new web application. I always version-control not only the .scss Sass source files that I myself write, but also the .css CSS files that Compass compiles from them. That way, anyone who checks out the project immediately gets a working web site without having to install Compass — or even having to know that it exists, if they are not themselves involved in writing the CSS.

But those of us who work on the CSS do need Compass, so I have a standard technique that I copy from project to project that installs Compass into a small, local Ruby environment, providing the same kind of isolation and reproducibility that Python has taught me to know and love thanks to virtualenv.

The process goes like this.

First I create a compass/ directory, typically up at the top level of the project, that initially contains nothing but a pair of shell scripts. The first script, install.sh, knows how to get Compass downloaded and installed:

#!/bin/bash
# compass/install.sh - install Compass under the "./Gem" directory

if ! which gem >/dev/null ;then
    echo 'Error: no "gem" command available'
    echo 'Please "sudo aptitude install rubygems1.8" or "ruby1.9.1"'
    exit 1
fi
BASE=$(dirname $(readlink -f $(which "$0")))
cd $BASE  # the directory where this script lives
gem install -i Gem compass
gem install -i Gem compass-susy-plugin

When this shell script is run, a compass/Gem/ directory gets created with the compass command down inside of it. To let me forget where the binary is located and how it can be safely invoked, a second shell script named compass.sh wraps up the details:

#!/bin/bash
# compass/compass.sh - properly invoke the "Compass" program

BASE=$(dirname $(readlink -f $(which "$0")))
export GEM_HOME=$BASE/Gem
export RUBYLIB=$BASE/Gem/lib
$BASE/Gem/bin/compass "$@"

I always tell my version-control system to ignore the compass/Gem/ directory and the 5,115 files that Ruby creates beneath it; instead, I simply remember to re-run install.sh after each fresh checkout when I want to get to work on the CSS.

When I first start a project, I need an initial set of .scss files to start editing, which can be supplied through the Compass command create. Usually I want the CSS output to be written somewhere outside of the compass/ directory, so my initialization steps go something like this:

$ cd compass/
$ ./install.sh
$ ./compass.sh create
$ rm -r stylesheets/    # where Compass wanted the output CSS!
$ emacs config.rb
# There, I adjust the line: css_dir = "../webapp/static/css"
# Plus, I also tend to set: line_comments = false
# Of course, use your editor-of-choice for this step!

I check into version control the config.rb file and the compass/src/ directory of pristine .scss files. I tell my version-control system to ignore the .sass-cache/ directory that gets created inside of compass/ each time the CSS is rebuilt.

Once those changes checked in, I never need to run the create command again for the whole lifetime of the project. Instead, whenever I am ready to work on the CSS, I simply open the .scss files in my editor and in another window I do this:

$ cd compass/
$ ./compass.sh watch

Just as a good development web server will auto-restart when you finish editing a file and hit Save, the Compass watch command will sit patiently all day and re-compile your Sass files to CSS whenever it sees you change them. By leaving it running, I can edit a .scss file and then hit Reload in my browser almost immediately to see the result without having to stop and run any intermediate commands.

The files, therefore, that wind up in my version control are these:

compass/compass.sh
compass/config.rb
compass/install.sh
compass/src/_base.scss
compass/src/_defaults.scss
compass/src/ie.scss
compass/src/print.scss
compass/src/screen.scss

And, of course, I also version-control the CSS files that Compass writes as output, over where I put them in the “main directory” of my web application:

webapp/static/css/ie.css
webapp/static/css/print.css
webapp/static/css/screen.css

This all works out extremely well. Normal developers and deployers look under the webapp/ directory and see what looks like normal, if preternaturally well-written and organized, CSS files exactly where they expect to find them. Only we CSS geeks on the project know that they are written by shuffling over to the Compass directory and firing up a program that compiles them from simpler source files. And thanks to my handy little pair of shell scripts, the Compass install itself is always completely automated.

Of course, as you can tell from the error message that install.sh prints if it cannot find Ruby, these scripts are aimed at an audience using Ubuntu or Debian. Please note in your comments to this post how you might expand those instructions to help people using Fedora, MacOS X, or other operating systems!

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