CSS

I’m working on making Drupal 8 faster as part of my job at Acquia. The focus has been on render caching¹², which implies that cacheability metadata is of vital importance in Drupal 8.

To be able to render cache all things that can possibly be render cached, Drupal 8 code must:

• set the right cache max-age — to ensure only the cacheable parts of the page are cached
• set the right cache contexts — to ensure content is varied as expected (per language, per role, per timezone, per user …)
• set the right cache tags — to ensure rendered content is invalidated when the data it depends on is modified

Before Drupal 8, approximately zero attention was given to cacheability of the rendered content: everything seen on a Drupal 7 page is rendered dynamically, with only the occasional exception.

By flipping that around, we make developers more conscious about the output they’re generating, and how much time it takes to generate that output. This in turn allows Drupal 8 to automatically apply powerful performance optimizations, such as:

I already mentioned the CSS sprite generator in my article on Drupal’s page loading performance. More great news though: they open sourced it! See the blog posts by the authors, Stuart Colville and Ed Eliot.

It’s under the BSD license though, so it would never be accepted on Drupal’s code repository, which is a must. I contacted the authors, asking if they would be willing to dual-license it under the GPL.

The effects of such a module – if technically possible to generate CSS sprites completely autonomously – would be enormous. It would reduce the number of HTTP requests per page considerably: all CSS background images would be aggregated into a single image!
Even on “just” the Garland theme of a default Drupal 6 installation (this includes a logo and a small Drupal banner at the bottom), this would save 7 HTTP requests per page.