Firehacks

What is this?

A very minimalist collection of persistent CSS and JS customisations of Firefox that bypass the limited modern extension API (which caused a great extinction event of user control over the interface).

To celebrate the arrival of native vertical tabs in Firefox (only about 20 years late) I got rid of my third-party tab extension, and immediately missed the lack of per-domain colours.

I found out that it's still possible to re-enable userChrome.js functionality using an autoconfig hack, although it's really difficult to find out how exactly because so much information is a decade out of date. Then I set out to fix all the usability annoyances that I absolutely can't stand, some of which I've been fixing in a much less convenient way. I've got all the most important things working, and will probably extend this solution to a few more in future.

This is my personal set of tweaks, which I intend to maintain only for the latest version of Firefox on Ubuntu installed as a deb package from the Mozilla repo. Feel free to fork this repository and use these files as a starting point for your own tweaks, entirely at your own risk. These modifications are not officially supported by Mozilla. You might break something. Please back up your profile and don't run with scissors.

Features

• Tab backgrounds are coloured by base domain, with an overlaid second colour for subdomains (or by scheme if there is no domain). www. is stripped off.
• GitHub tabs are overlaid with colours for the first two path elements (usually account and repository).
• Clicking once in the URL bar or search bar never selects the contents.
• The search term is cleared from the search bar after the search is performed.
  • Focus is also always restored to the current tab.
• Searches performed from the search bar that load in new tabs always load in background tabs and never switch focus away from the currently selected tab.
  • This does not affect the search being opened in the current tab when it is blank, or searches from the URL bar opening in the current tab.
  • Context menu searches still switch focus to the new tab; I never use this feature, but maybe I'll fix it anyway for consistency.
• Unread tabs have an unread attribute again and can be styled.
  • Tabs restored from a previous session start off as unread; you can exclude them with a different attribute.
• Tab styles for unread, selected, and hover.
• Webpage links on the new tab page have no titles.
• Pinned tabs are smaller and tab padding is reduced (and fixed).

How to use

You need root access. I have no idea how to set this up on any system except my own, but it should go something like this:

• firehacks.js has to be in the same directory as the firefox executable. On Ubuntu with the deb package that's /usr/lib/firefox/.
• autoconfig.js has to be in /defaults/pref/ relative to that directory.
• All the CSS files go in the chrome subdirectory of your Firefox profile.
• You have to enable toolkit.legacyUserProfileCustomizations.stylesheets in about:config.
• There are two preferences for these tweaks:
  • extensions.firehacks.num_hues: how many different hues to use to colour tabs (minimum: 1; maximum: 360)
  • extensions.firehacks.hue_offset: an offset to apply to the hues (in degrees)
• If you change anything in any of these files, or the preferences, you have to restart Firefox for the changes to be applied.

How to develop

I recommend enabling the Browser Toolbox, and using it in conjunction with the browser console. There are lots and lots of legacy user scripts online to examine for examples of similar code. Some of them use old APIs and don't work at all, but some work with minor modifications.

Alternatives

There are multiple generic loaders which restore the functionality of loading arbitrary scripts from the chrome directory in your profile, and collections of updated scripts made to work with them. I decided that they were overengineered and undersecured for my simple use case, hence this project.

Possible future work

• Prefs to turn unrelated hacks on and off
• Make some prefs apply immediately, for easier testing
• Extend mouse gestures only to restricted pages
• Basic related tab grouping / indentation; would need to integrate with reordering
• Refactoring into a separate object
• Integration with other extensions

Recommended related extensions

• uniqtabs, a small extension that deduplicates and sorts your tabs. It didn't play nicely with the vertical tab extension, but it works great with the native tabs and the colours and now I use it all the time.
• Foxy Gestures for mouse gestures.
• Violentmonkey, for user content scripts.
• Stylus, for user content styles.