Difference between revisions of "LESS"

Revision as of 13:40, 28 September 2015 (view source) Nadav Kavalerchik (talk | contribs) (→‎Installing Recess) ← Older edit		Revision as of 13:43, 28 September 2015 (view source) Nadav Kavalerchik (talk | contribs) (→‎Installing Recess) Newer edit →
Line 17:		Line 17:
	== Installing Recess ==		== Installing Recess ==
−	As of August-2015, "recess - no longer maintained, does not work with newer less versions" : https://github.com/twitter/recess .	+	As of August-2015, "recess - no longer maintained, does not work with newer less versions" : https://github.com/twitter/recess .
−	Better use lessc or other alternatives.	+	Better use [http://lesscss.org/#using-less-installation lessc] or other alternatives.
	=== Ubuntu ===		=== Ubuntu ===

---

Revision as of 13:43, 28 September 2015

Overview

LESS (lesscss.org) 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. There are many others tools for LESS.

The bootstrapbase theme

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

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

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

Installing Recess

As of August-2015, "recess - no longer maintained, does not work with newer less versions" : https://github.com/twitter/recess .

Better use lessc or other alternatives.

Ubuntu

The following commands should be run to install Recess

sudo apt-get install npm nodejs
# If the above fails due to the error "The following packages have unmet dependencies",
# run the commands separately, ie.
#     sudo apt-get install npm
# and then
#     sudo apt-get install nodejs
npm install recess -g
# If the above fails with a "..permission denied.." error,
# run npm install with sudo:
#     sudo npm install recess -g

If you find problem installing nodejs with npm, you can use node.js binaries

1. Download Linux Binaries node.js binaries
2. untar it to your local directory and add it to the PATH.

You can also use following script to get latest version.

CURRENT=$(node -v)
VERSION=$(curl -L -s http://nodejs.org/dist/latest/ \
    | egrep -o '[0-9]+\.[0-9]+\.[0-9]+' \
    | tail -n1)
PLATFORM=linux
ARCH=x64
PREFIX="$HOME/node-v$VERSION-$PLATFORM-$ARCH"
 
if test "v$VERSION" != "$CURRENT"; then
    echo "Installing node v$VERSION ..."
    mkdir -p "$PREFIX" && \
    curl -# -L http://nodejs.org/dist/v$VERSION/node-v$VERSION-$PLATFORM-$ARCH.tar.gz \
      | tar xzvf - --strip-components=1 -C "$PREFIX"
    echo 'export PATH=$PATH:'"$PREFIX" >> $HOME/.bashrc
    echo "Latest stable version installed at $PREFIX"
else
    echo "Latest stable version of node already installed."
fi

npm

stands for Node Package Manager, and is the equivalent of apt-get for node.js packages.

Mac OS X

1. Install the basic node packages from the web site: http://nodejs.org (or use your favourite package manager to install

node

and

npm

).

2. On the command line, install recess like this:

npm install recess -g

FreeBSD

1. Install npm (will also install nodes ie nodejs as a dependency)

Using packages on:

pkg install npm

Build port in /usr/port/www:

cd /usr/port/www/npm; make install clean

Using portmaster:

portmaster npm

2. On the command line, install recess like this:

npm install recess -g

Windows 7, 8, & 10

In order to install Recess you need to have Node.js installed first, which is relatively simple to do.

Go to nodejs.org click install.

When installed go to -> Start -> All Programs -> type Node.js into the Search box, then select Node.js Command prompt (black icon) from the list. Now you are ready to install Recess. So at the command line prompt type the following:

npm install recess -g

npm

stands for Node Package Manager, and is the equivalent of apt-get for node.js packages.

Using Recess

After editing the LESS files, compile (minified) your CSS as follows:

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

or if you prefer to run it from the top-level:

recess --compile --compress theme/bootstrapbase/less/moodle.less > theme/bootstrapbase/style/moodle.css

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

Alternatively if you want to view the normal (un-minified) CSS then use the following method.

recess --compile moodle.less > ../style/moodle.css

NOTE: if you are getting an empty moodle.css file, this is being caused by a parsing error in your LESS code. A bug in

recess

currently prevents it giving you helpful error messages in many cases. You will need to examine what you have altered or written to make sure it is complete and the syntax is correct. The

lessc

compiler is what is used by

recess

to do the actual compiling and will have been installed automatically along with it. If you call it directly as

lessc moodle.less

it should give you a helpful error message that points you to where the problem is.