LESS

Overview

LESS extends CSS with dynamic behavior such as variables, mixins, operations and functions. It's an advanced way of writing CSS that we use in some themes within Moodle.

Browsers don't interpret it themselves, however, so LESS files need to be converted into normal CSS before use.

Recess is one tool used to compile and compress LESS into CSS under *nix based systems.

For Windows users, WinLess is available to compile and compress LESS into CSS for you.

The bootstrap theme

Moodle's bootstrap base theme has rules written using LESS.

The main LESS file is theme/bootstrap/less/moodle.less, with additional files in theme/bootstrap/less/moodle/ imported by the main file.

After compiling the LESS files, CSS ends up in theme/bootstrap/style/generated.css. This file should not be edited manually.

Installing Recess under Ubuntu

The following commands should be run to install Recess

sudo apt-get install npm node
npm install recess -g

Installing Recess under Mac OS X using MacPorts

1. Install MacPorts on Mac OS X. If you use a different package manager some install commands will vary.

2. Install npm, the Node package manager

    port install npm

3. Install recess

    npm install recess -g

Depending on your shell, you may need to type rehash after installing for your shell to pick up the commands.

Using Recess

To compile to LESS for the boostrap theme use these commands, from the root of your Moodle code directory

cd theme/boostrap/less/
recess --compile --compress moodle.less > ../style/generated.css

This will compile and compress the moodle.less file (and all the LESS and CSS files it imports) into a single file, generated.css, and store it in the style folder of the bootstrap theme.

NOTE: if you are getting empty generated.css files, this is being caused by a parsing error in your LESS code. You will need to examine what you have altered or written to make sure it is complete and the syntax is correct.

WinLess under Windows

Download WinLess and install it.