Using Less as a live CSS engine

Following on from my last post on CSS pre-processors, there is an interesting guest post over at CSS Tricks—from Andrew Powers of PageLineson using Less as a live CSS engine.

It seems that PageLines—who craft WordPress Templates—actually use Less as a live CSS engine for enabling customers to change settings in their templates.

How we implemented it

For us the the key to executing a live LESS engine was this port of the LESS processor to PHP (link) which allowed us to parse and cache LESS files based on user action on our server. To get this working the framework just does the following.

  • Grabs all the LESS files throughout the framework and adds them to a PHP variable
  • Uses the above PHP script to parse the LESS into CSS and puts it in a variable
  • Outputs the CSS to a file which is cached both on the server and on visitors browsers
  • The process is run again whenever a user saves their settings or installs a new extension

This is extremely interesting because, ever since I started using Less, I have been contemplating using it for precisely the same thing within our company’s CMS.

Right now, our CMS uses a very advanced Dynamic Templating System (DTS) which reconfigures the page depending on what the user has placed on it, i.e. if you place a widget in the left-hand column, then it will generate a left-hand column; if you don’t, it won’t.

However, currently, all of the aesthetic styling has to be done by our own implementers; however, with the advent of multi-site functionality in our CMS, we are seeing an increased demand for advanced users to be able to make changes themselves.

Although we have implemented a system where aesthetics can be saved as Custom Style Presets—which can then be applied by the user—we have to write those presets first.

Ideally, we would actually allow the user to change certain colours themselves—but that leads to all sorts of complications that, in the end, would constrain our designers and deliver only partial control to the user.

Using Less as a live CSS engine is the way to get around this problem. However, since our system is not written in PHP, we would need to see if Less has been ported to ColdFusion (unlikely) or write the plugin ourselves (not currently a priority).

Whichever way we go with this, it is nevertheless great to see that there is an operating version of this concept being deployed in the wild.

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