XUL/XBL Replacement Newsletter 13

This is the thirteenth edition of the XUL/XBL Replacement Newsletter. Since the last edition, we’ve gotten close to shipping the main browser window as an HTML document, made some platform improvements related to ongoing frontend work, and continued to remove XBL bindings.

Progress towards browser.xhtml

We’ve gotten close to shipping the main browser window as XHTML instead of XUL. In addition to the broader top-level HTML support which is now complete, we filed a new metabug specifically for shipping browser.xhtml.

The biggest piece of work here was Brendan Dahl adding prototype cache support to XHTML documents. With this change we are seeing equivalent performance between browser.xul and browser.xhtml.

As part of that project, he also added <html:template> support to documents loaded with the prototype cache. This is a nice change to bring our chrome UI more in line with the Web platform and gives us a more standard way to lazify DOM creation (there’s a metabug to do so).

The final steps before enabling browser.xhtml are fixing some assertions (1, 2) that surfaced due to nsHTMLDocument being a DOM proxy and XULDocument not being a proxy. Once those are resolved we plan to flip the switch to enable browser.xhtml by default.

Platform improvements

I wanted to mention some platform improvements and code removal related to these projects, and acknowledge the people who’ve worked on them. These are mostly changes that were unblocked by removing in-content XBL and XBL stylesheets, and fixes for bugs we’ve discovered from dogfooding Web Components in the browser chrome.

Binding Removals

There are 44 bindings left, compared to 55 from the last update and 300 from the start of the project. Here’s a list of changes: