Photon Engineering Newsletter #16

Time to get your groove on! It’s Photon Newsletter #16!

But first. Do you remember the 21st night of September? As of today (September 21st) Firefox 57 has passed its penultimate milestone by entering Beta. This is a pretty big deal, as it means many millions of users on Beta will soon experience all the awesomeness that’s packed into 57. Note that Beta builds won’t actually go out until next week, on the 26th. But if you’re running Developer Edition, we’ve already pushed out an early sneak-peek!

Did I mention that Developer Edition also got a snazzy new Firefox icon? It’s nice. And blue.


The past week has been very busy as we’ve been doing a major burst of bug triage, just to make sure we’re not missing any already-reported critical issues. The front-end teams went through nearly 600 untriaged bugs in just a few days! The good news is that we didn’t find anything alarming, which matches up with our general impression that 57 is shaping up to be a really solid release.

Recent Changes

  • Investigation is ongoing into bug 1397092, where a user has reported an interesting case of high cpu usage possibly caused by the new tab loading indicator
  • The tab loading indicators are now synchronized, so when multiple tabs are loading the “bouncing balls” move left and right in unison.
  • The Animation team is shifting focus to help with polish bugs in the Visual Redesign and Menus/structure areas, as most remaining animation bugs are lower priority.
  • All P1 bugs landed – MVP feature-complete!
  • Added a setting to bring back the search box. With 57 it won’t be added to newly created profiles, but can be restored through Customize Mode. By adding additional preferences UI we hope to make is as easy as possible to get it back for anyone wondering where it went.
  • Did a UI review, and landed a batch of polish fixes to address a number of minor issues found.
  • Deferred the loading of some information to improve the amount of time it takes to open the main Preferences page.
Visual redesign:
  • Fixed a white flash in the content area when opening new tabs and new windows, which made things look janky.
  • Separately, fixed a flickering in the awesomebar results when updating search suggestions.
  • We had to disable tab warming when hovering tabs, because it caused more regressions than we are comfortable fixing for 57. We are now planning to ship this significant perf improvement in 58.
  • Our dashboards show very good wins on all things we measure when comparing 55 to 57. Eg. startup is about 50% faster in 57 than it was in 55!
  • Not planning any further significant performance work for 57, to avoid risk of causing regressions. We are starting to look at what improvements can go into 58/59, and where we should put performance efforts in the longer term.

That’s all for now. There are only a few more weeks for us to do more polish work in 57 Beta, so there will probably only be a few more Engineering Newsletters as well. (But fear not, there’s been such positive response to these newsletters that we’ll likely continue them post-Photon in some form.)

11 thoughts on “Photon Engineering Newsletter #16”

  1. > The overflow panel now has rounded corners on macOS

    Will this UI change of rounded corners make it to the Linux versions?
    Awesome job none the less!

  2. Are there any plans to implement the dark theme in places like the bookmarks sidebar? I love having the sidebar open now and would just really love it, if it matched the rest of the dark theme.

  3. Is there a chance for vertical tabs anytime soon in mainline Firefox?

    Tab Center has been in Firefox Test Pilot, but the report is still not available.

  4. Thanks for the updates.

    Something I noticed: the pictures/animations are hard to recognise, because of scaling/compression. I saw that those are scaled down presumably by wordpress, and added a GET parameter for width. Removing this shows the clear, original sized image. Would be nice if you linked the original size on those images for future posts.

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