Livestyle

Livestyle is a small web server that refreshes the stylesheets on your web sites live as you edit them.

It does so by injecting a small JavaScript client on each html page, which subscribes to changes on the served css files through a WebSocket (via socket.io).

The server then notifies the client to reload specific stylesheets when they are updated on the file system.

The livestyle client also falls back to active polling, which means you can use the client as a standalone script on your normal web server.

Use livestyle to get live feedback while staying in your favorite editor. Effective use cases spotted so far:

• Styling parts of web applications that require several clicks to get to the state you are working on.
• Getting instant feedback from many browsers at the same time, including mobile browsers!
• Testing several media queries at the same time with different devices or browser window sizes.

If you are looking for a grunt task doing the same, take a look at grunt-livestyle.

Usage

Livestyle installs an executable script on your system called livestyle.

To get started quickly just change the directory to where your document root is and run the livestyle command. The server will now listen on port 3000.

Here's the full set of command line options:

--root|-r <dir>

The directory to serve static files from. Unless --proxy is specified, it defaults to the current working directory. If you want to serve static files in --proxy mode, --root must be specified explicitly.

--host|-h <hostNameOrIp>

The local hostname or IP-address to listen on. Defaults to 0.0.0.0.

--port|-p <portNumber>

The local post number to listen on. Defaults to 3000.

--proxy http://<hostname>[:port]/

Instructs livestyle to proxy requests for everything but CSS files to a remote server, as determined by the Accept request header.

--map|-m <sourcePathPrefix>=<targetPathPrefix>

Translate the paths of incoming requests. Think of it as a very primitive mod_rewrite that only works on request path prefixes. For example, to translate all requests for /foo/* to /bar/*, use this switch: --map /foo/=/bar/

Multiple --map switches are allowed. When used in conjunction with --proxy, the mappings are applied before proxying the request.

--compiless

Compile less assets on-the-fly using express-compiless. Also supports watching @import'ed less assets.

--compilesass

Compile sass assets on-the-fly using express-compile-sass. Also supports watching @import'ed sass assets.

--autoprefixer

add missing css vendor prefixes on the fly using express-autoprefixer

If you only provide the flag with no value (like this: --autoprefixer) it will use the autoprefixer defaults. '> 1%, last 2 versions, Firefox ESR, Opera 12.1'.

You can pass options as a string of supported browsers separated by comma. For syntax and valid options see the autoprefixer projectpage.

If you wish to support IE9 and the last 2 versions of every browser you should provide the options like this: --autoprefixer "ie > 8, last 2 versions".

--jsxtransform

If this value is set, JSX code (used in facebook/react will be compiled to javascript on the way out. Using express-jsxtransform.

--processimage

Process images on the server according to the query string using using express-processimage.

--watchhtml

Also watch the HTML file itself and refresh if it changes on disc.

--watchcssimages

Also watch (background) images used by CSS and refresh them if they change on disc.

--debug|-d

Outputs a bunch of debugging information on both the server and the client.

--watchfile=true

If set, will use fs.watchFile instead of fs.watch. If you experience problems that the server stops watching a file after the first time you save a file, this method will help.

--mtime

Only notify clients about a changed file if its mtime has increased. Experimental, only supported when using fs.watch.

Installing livestyle

Livestyle requires NodeJS and npm to be installed. See this page for installation instructions: https://github.com/joyent/node/wiki/Installation

When the prerequisites are in place, run the following command:

npm install -g livestyle

And you are done.

Supported platforms

Livestyle uses pure web technologies. It uses WebSockets if possible, but falls back to polling via XHRs. This means that every non-ancient, JavaScript-enabled browser should be supported, also on mobile.

Currently there are some troubles with updating stylesheets using @import in IE, which you want to avoid anyway http://www.stevesouders.com/blog/2009/04/09/dont-use-import/

Module loaders

Livestyle supports asynchronous loading and injection of stylesheets. If you are using requirejs you might want to take a look at css.js and less.js, wich can be used as module loaders for both less and css files using requirejs like so:

define([
    'less!bootstrap/theme.less',
    'css!styles/myLoginBox.css'
], function () {
    // My module depending on certain styles
})

These two loaders are both usable without livestyle. The less.js loader will change behavior depending on wether you have set the --compiless flag for livestyle to make live updates possible.

Help! fs.watch throws ENOSPC errors!

You are hitting the limit of inotify watchers on your system. To remedy this, you can increase the limit. On modern computers it should not be worsening the performance significantly.

To check what your current limit is run:

$ cat /proc/sys/fs/inotify/max_user_watches

It should generally be safe to just double that if you see this error.

$ echo 16384 > /proc/sys/fs/inotify/max_user_watches

You will need to run the above command with super user privileges.

To make the change permanent you can add the following line to the /etc/sysctl.conf file.

fs.inotify.max_user_watches=16384

This solution is assuming you are running Debian.

CSS preprocessors

Since livestyle watches the css files that are actually served to the browser, livestyle work with any CSS preprocessor that runs on the server out of the box.

If you want live updates you will of course need to enable your preprocessor's option to automatically build a new CSS files for each file update. livestyle will then detect the update in the built file and push it to the client.

There are two CSS preprocessors that run in the browser, which is a bit of a special case:

Prefixfree

Prefixfree inserts vendor prefixes for the style properties that need them. It does this runtime in the browser by fetching the stylesheet content through XHR and replace the link tags with a style block with prefixed CSS. Livestyle now supports prefixfree.

Less.js

Less.js injects preprocessed style into the page by loading .less files and reworking the content to real CSS. Livestyle supports live updates using Less.js by refreshing all less stylesheets on the page.

License

LiveStyle is licensed under a standard 3-clause BSD license -- see the LICENSE-file for details.