Firefox throws the XUL layout overboard: The XML User Interface Language was previously used to render the graphical user interface of the web browser. However, since the latter is a regular website under the hood, regular and widespread web technologies such as HTML elements and CSS will be used for the UI in the future.
There was only XUL
What was the XUL all about? The GUI language dates back to Mozilla’s history when it started with Netscape in 1997 and found a future in Firefox with the release of the browser and the new name a year later. In fact, XUL offered more features than HTML4, was also used in other Mozilla projects and their forks – and there was initially openness from third-party developers to use the language for their UI. With HTML5, however, interest in it waned.
In his announcement that the XUL layout is now a thing of the past, Mozilla developer Emilio Cobos Álvarez unadornedly named the language’s weaknesses: First, it never supported some popular CSS features. Furthermore, the software was poorly documented and there was no active maintainer. Anyone wanting to work on Firefox not only had to learn the XUL idiosyncrasies, they also lacked the related information. In addition, according to Álvarez, the consistent use of weaving technology also promises an increase in speed and fewer bugs.
Reach your goal via emulation
Im Bug 1033225 shows that it took nine years for the developers to make the switch. Mozilla also publicly announced the step back in 2015 – with a medium-term schedule. Alvarez shows in his blog also, what difficulties the Mozilla team had to contend with and how they managed a smooth transition between the XUL and web technology: Due to the complicated and extensive code, the transition could not be managed in one big step. Rather, an incremental approach was offered, in which the programmers could test and understand the effects of their changes using an XUL emulation.
So Firefox can now do completely without the XUL? Not quite: OS native panels and menus will have to be added by developers in the now deprecated language as usual.
(fo)
