[kuschku]

> Part of the decision has already been made. We are moving Firefox addons (themes and extensions) away from a model where you can perform arbitrary styling or scripting of the browser chrome. This is an engineering-driven decision, and it's unavoidable and necessary for the long-term health of Firefox. Not only are we moving Firefox away from XUL, but we are likely going to make significant changes in the way the UI is structured. It is likely that some parts of the UI will be implemented using native widgets, and other parts will be implemented in HTML, but the exactly DOM structure may involve independent connected with well-defined API surfaces.

Official statement from the Mozilla post in the discussion regarding removal of support for "heavyweight" themes. Emphasis mine.

That’s a pretty clear statement that it won’t be 100% HTML.

Also, the fact that "arbitrary styling and scripting" won’t be possible is another issue.

Tell me how I am supposed to write an addon that adds tab-previews as thumbnails when you hover over a tab like Vivaldi is doing it: http://i.imgur.com/vqysJs1.png ?

How am I supposed to write an addon that colors the navbar and the current tab in the theme color given by the HTML, or, if not existing, the favicon?

With current addons I can do that, with the new addon system, I’m seriously fucked.