Setting up for Android and Firefox OS Development

This post is a follow-up to an earlier article I wrote about setting up a FirefoxOS development environment.

I’m going to set up a Sony Z3C as the target device for Mobile OS software development. The Sony Z3C (also known as Aries or aosp_d5803 ) is a nice device for Mobile OS hacking as it’s an AOSP device with good support for building the OS binaries. I’ve set the phone up for both FirefoxOS and Android OS development, to compare and see what’s common across both environments.

Please note that if you got your Sony Z3C from the Mozilla Foxfooding program, then this article isn’t for you. Those phones are already flashed and automatically updated with specific FirefoxOS builds that Mozilla staff selected for your testing. Please don’t replace those builds unless you’re actively developing for these phones and have a device set aside for that purpose.

My development host is a Mac (OSX 10.10) laptop already set up to build the Firefox for Macintosh product. It’s also set up to build the Firefox OS binaries for the Flame device.

Most of the development environment for the Flame is also used for the Aries device. In particular, the case-sensitive disk partition is required for both FirefoxOS and Android OS development. You’ll want this partition to be at least 100GB in size if you want to build both operating systems. Set this up before downloading FirefoxOS or Android souce code to avoid ‘include file not found’ errors.

The next step to developing OS code for the Aries is to root the device. This will void your warranty, so tread carefully.

For most Gecko and Gaia developers, you’ll want to start from the base image for the Aries. The easiest way to flash your device with a known-good FirefoxOS build is to run in the expanded file from the official builds. You can then flash the phone with just Gecko or Gaia from your local source code.

The Aries binaries from a FirefoxOS build:


The Aries binaries in an Android Lollipop build:


If you want to build Android OS for the Aries, then read these docs from Sony, and these Mac-specific steps for building Android Lollipop. Note that the Android Lollipop SDK requires XCode 5.1.1 and Java 7 (JRE and JDK.) Both versions of XCode and Java are older than the latest versions available, so you’ll need to install the downgrades before building the Android OS.

When it comes time to configure your Android OS build via the lunch command, select aosp_d5803-userdebug as your device. Once the build is finished (after about 2 hours on my Mac,) use these commands to flash your phone with the Android OS you just built:

fastboot flash boot out/target/product/aries/boot.img
fastboot flash system out/target/product/aries/system.img
fastboot flash userdata out/target/product/aries/userdata.img

Firefox Platform Rendering – Current Work

I’m often asked “what are you working on?” Here’s a snapshot of some of the things currently on my teams’ front burners:

I’m surely forgetting a few things, but that’s a quick snapshot for now. Do you have suggestions for what Platform Rendering features we should pick up next? Add your comments below…

Gaia Tips and Tricks for Gecko Hackers

I’m often assigned Firefox Rendering bugs in bugzilla. By the time a bug gets assigned to me, the reporter had usually exhausted other options and assumed (correctly) that I’m ultimately responsible for fixing Firefox rendering bugs. Of course, I often have to reassign most bugs to more capable individuals.

Some of the hardest bugs to assign are the ones reported by our own Gaia team: the team responsible for building the user experience in Firefox OS. The Gaia engineers take CSS and JavaScript and build powerful mobile apps like the phone dialer and SMS client. When they report bugs, it’s often found within lots of CSS and JS code. I wanted to learn how to effectively reduce the time it takes to resolve rendering issues reported by the Gaia team. It takes a long time to go from a Gaia bug like “scrolling in the gallery app is slow” to find the underlying Gecko bug, for example “rounding issue creates an invalidation rectangle that is too large.”

To do that, I became a Gaia developer for a few days at our Paris office. I reasoned that if I could learn how they work, then I can help my team boil down issues faster and become more responsive to their needs. We already recognize the value of having expert web application developers on staff, but we could do a better job with a better understanding of how they work. With that in mind, I spent the week without any C++ code to look at, and dived into the world of mobile web app development.

I wrote down the steps I took to set up a FirefoxOS build and test environment in an earlier post This time, I’ll list a few of the tips and tricks I learned while I was working with the Gaia developers.

The first and most important tip: You will brick the phone when working on the OS. In fact, you’re probably not trying hard enough if you don’t brick it :) Fastboot lets you connect ADB to the phone when it becomes unresponsive to flash the device with a known good system (like the base image.) Learn how to manually force fastboot on your phone.

Julien showed me how to maintain a Gaia developer profile on your desktop development environment. This set of commands will configure your B2G build to produce the desktop B2G runtime that’s a bit easier to debug than a device build:

# change value of the FIREFOX to point to the full path to the B2G desktop build
 export FIREFOX=/Volumes/firefoxos/B2G/build/dist/
 export PROFILE_FOLDER=gaia-profile DEBUG=1 DESKTOP=0

With a Gaia developer profile, you can switch between B2G desktop and a regular Firefox browser build for testing:

export FIREFOX=/full/path/to/desktop/browser
 $FIREFOX -profile gaia-profile --no-remote app://

The Gaia profile lets you use URL’s like app:// to run the Gaia apps on the desktop browser. This trick alone was a huge time saver! Try it with other URL’s like app://

For a first Gaia development project, I picked up the implementation of the new card view for gaia that is based on an asynchronous panning and zooming (APZC.) Etienne did the initial proof-of-concept and my goal is to rebase/finish/polish it and add some CSS Scroll Snapping features. My initial tests for this feature are very promising. CSS Scroll Snapping is much more responsive than the previous JavaScript-based implementation. I’m still working out some bugs but hope to land my first Gaia pull request soon.

I’ve already been able to apply what I’ve learned to triage bugs like this one. The bug started out described as a problem with how we launch GMail on B2G in Arabic language. Based on the testing tricks I learned from Gaia team, I was able to distill it to a root cause with scrollbar rendering on right-to-left (RTL) languages. I added a simplified test case to the bug that should greatly reduce debugging time, and assigned it to one of our RTL experts. That’s quite a bit better than assigning tough bugs to random developers with the entire OS as the test case!

Thanks to Julien and Ettiene for helping me get up to speed. I highly recommend that any Gecko engineer spend a few days as a Gaia hacker. I’m humbled by the ingenuity these developers have for building the entire OS user experience with only the capabilities offered by the Web. We could all learn a lot in the trenches with these hackers!

What can SVG learn from Flash?

Regular readers of my blog know that I also worked on the Macromedia Flash Professional authoring tool and the Adobe Flash Player for many years. I learned a great deal about the design of ubiquitous platforms, and the limitations of single-vendor implementations. At a recent meeting with the W3C SVG working group, I shared some of my thoughts on how Flash was able to reach critical mass across the Web, and how SVG can leverage those lessons for the future.

Basically, it boils down to 3 principles:
1. Flash offered expressive design-fidelity across all user agents.
2. Flash authoring was superior to SVG authoring tools for producing content that adheres to principle # 1.
3. Most Flash content is self-contained and atomic in a packaged file format that helped preserve design-fidelity in # 1.

I shared some feedback regarding what I hear from Firefox users about SVG. I also shared what I never hear from Firefox users: “We need more SVG features.”

As the working group ponders new SVG specifications for review, the main gripe I hear from users is the lack of interoperability for the current feature set. That is, I don’t get requests for a new DOM or fancy gradient meshes, I get bugs about basic rendering differences across browsers. As a result, I’ve directed our SVG investment towards these paper cuts that make authors distrust SVG for complex designs. I can see why it’s more tempting to focus on new feature specifications, but adoption is hampered by the legacy of interoperability (or lack thereof.) I’d like to see the group organize around fixing these bugs across all browsers in a coordinated fashion, eg. in a hackathon or bug bash at a future multi-browser face-to-face meeting.

I also talked about how SVG could be a very expressive authoring source format for a modern implementation that is more focused on pixel-fidelity. Unfortunately, I didn’t get a lot of support for that idea from other browser vendors, as the desire to compete for the best implementation seemed to outweigh the benefits of dependable runtime characteristics. I’m really surprised that SVG hasn’t stepped in to replace Flash for more use cases, and I’m quite certain that the 3 principles I mentioned above are the reason why. I do hope that authoring tool vendors step in and help drive the state of the art here. It’s one thing for browser vendors to offer competing implementations, but the lack of strong authoring systems makes it hard to define what it means to be correct.

I spoke with a few people about how the packaged SWF format was an advantage for Flash because it was easy to have this content move across the internet in a viral fashion without losing any of the assets. Flash games, for example, are commonly hosted on multiple servers (often unknown to the original publisher) and still retain all the graphics and logic within the SWF file. The W3C application package proposal is something we could implement as a format that lets HTML/SVG content traverse networks intact. It’s not hard for such HTML/SVG applications to be made up of hundreds of individual assets that are easy to lose track of. Having a packaged format with clear semantics and security rules (eg. iframe in a zip) could be a really good feature for the modern web.

What else are we missing for SVG to gain critical mass? Post a reply below or find me on twitter!

An imposter among you

I’m blessed to live and work with the smartest people I know. I’ve been at it for many years. In fact, I’m quite certain some of them are among the smartest people on the planet. I cherish the knowledge and support they freely share yet I frequently wonder why they tolerate me in their midst.  I’ve experienced Imposter Syndrome from an early age, and I’m still driven to tears when I think about it. Why do I deserve to be in the midst of the greatness I’ve surrounded myself with? It’s worse when I get credit, as I feel like I’ll surely be figured out as the fraud now that everyone’s looking.

I’ll just leave this here as I suspect there are many others around me who have this affliction. If nothing else, I’m right there with you—for real.

FirefoxOS Dev Quick Start

B2G_dev_envI’m posting the steps I took to create the FirefoxOS dev environment for the Flame device. We use the Flame as our reference device on the Platform Rendering team. I had to re-do this recently on a new computer and I figure this might help others in the same boat. These steps assume you can already build the desktop version of Firefox on your computer.

  1. Get ADB
  2. Turn on ADB debugging on your device.
  3. Download the latest base image ( at the time of this writing.)
  4. Unzip the base image archive and run the script to update your phone to the latest base image. You’ll need to re-enable ADB debugging after this step.
  5. Clone the B2G repository and follow the prerequisite steps for local builds.
    Note: the device we target for the step is flame-kk (not the older flame device.)
  6. Get a coffee and wait for the long source download.
  7. Run ./ in the B2G source directory to build.
  8. Run ./ in the B2G source directory to put your new build on to your phone.

NYC Indie Web Camp Weekend

Indie Web Camp logo

I’m at the NYC Indie Web Camp this weekend at the beautiful New York Times office in Manhattan. Tantek Çelik joined my team at Mozilla about six months ago to work on various Web Standards initiatives that we push forward on the Firefox Platform team. Although our bread and butter is Web Platform Rendering, Tantek is also passionate about advancing user-sovereignty to enable authorship outside of proprietary corporate silos (see POSSE.) I tagged along with him this weekend to learn more.

The Indie Web movement is in the midst of an exciting creative stage. There are people hacking on the building blocks and other folks dogfooding the code. At this point, I’m in the latter camp, looking to solve 2 problems that I have with my 3 web sites:

  • – this blog for stuff about various things that I do with the geeks I hang out with (dare I say, my network.)
  • – a site to catalog the products I make that happen to also pay my bills.
  • – a site to describe non-profit activities (music and other hobbies) that I engage in. I haven’t found much time to write about this stuff lately.

Problem 1: When I first decided to split my online life into 3 top-level domains, I thought it would help organize my efforts into those 3 top-level buckets. It turns out that, in practice, I’ve just split my online persona into 3 sites in various states of intermittent activity. I’d like to try and organize the 3 buckets so that I can post content in any category (org,com,net) and have the posts go to the right site, while still aggregating on this blog. Fortunately, I met Jeremy Zilar this weekend and he works on the 200+ Blogs for The New York Times. My 3 site problem dwarfs in comparison to what the Times has to scale. I’m loving all the brainstorming going on this weekend.

Problem 2: I’d like to make a few bucks on these sites without the usual ad-generated methods. It’s not that I’m above receiving advertising revenue, I just think my audience is a very narrow slice of the geek population that is also very good at not clicking on ads. I would instead like to sell them my stuff. I might sell a single sweatshirt or an extra torque wrench that I happen to have lying around. I’d like to do this in an Indie Web way as I am, in effect, inviting you to a virtual private garage sale (VPGS?) I’m looking into various Web Payments solutions to do this.

I’ve added the IndieWeb plug-in to my WordPress sites so I can send and receive various notifications over IndieWeb protocols like WebMention. I expect to hack on various bits of the solution to these 2 problems as I learn more. I’ll share the code here, in case others may find it helpful.

I’m also interested in extending the Web Platform to enable more Indie Web capabilities at the core of the Open Web stack. It’s really exciting and fun to work on this stuff. What else can we do to make it easier for user-authors to raise their independent voice?

Platform Rendering Work Weeks in Taipei

The Platform Rendering team is back in Taiwan this month. This time, we’ve split the team across 3 work weeks (Media, Layout, and Graphics.) This lets us focus on the issues specific to each team but still allow for free time to hack and socialize.

Here’s the week’s agenda for the Platform Media team:

10th March
11th March
12th March
13th March
14th March
10:00 – 10:55 Introduction / Lightning talks
Anthony Jones
Platform Decoder Modules, MP4
Chris Pearce
Media Stream Graph Refactoring
Paul Adenot
Stingray – Introduction and demo of TV
Content enablement session
Chris / Ide
11:00 – 11:55 Beginner’s guide to <video> code
Chris Pearce
“MediaCodec for playback”
Bruce Sun
“Video Codec Resource
Blake Wu
“Adjust priority/nice value for media playback threads”
Star Cheng
JW Wang
Stingray – Introduction of hardware
Shumway (Mozilla Flash Player)
Jet Villegas
13:00 – 13:55
14:00 – 14:55 Process reflection
Anthony Jones
Async Decoder Changes
Chris Pearce
Tim Terriberry
Stringray – AV related achetecture
TaskTracer Demo
Shelly Lin
4th floor, Mozspace
15:00 – 15:55 Pre-Discussion about Panasonic TV
Shelly Lin
New Recording Features
John Lin
Video Recording
Randy Lin
Seccomp etc
Paul Terriault
Stringray – GFX related achetecture
Hell Kitty
Chris Pearce
16:00 : 16:55 Manager Session
Anthony Jones
Chaos mode debugging and rr
Robert O’Callahan
Media Source Extensions
Chris Double
Our Proposals for Panasonic TV
Shelly Lin
Chris Pearce
19:00 – Team dinner @ Din-Tai-Fung, Taipei 101

Here’s the week’s agenda for the Platform Layout team:

Monday Tuesday Wednesday Thursday Friday
9am SVG buffered-rendering (small group) Elephant Mountain walk
10am lightning talks (jet) Shipping CSS Variables (heycam) Vertical Text (smontagu) OMTA (birtles)
11am position:sticky (kip) CSS scroll snapping (roc) Platform Priorities (jet) CSS flexbox (dholbert)
Noon Lunch Lunch Lunch Lunch Lunch
1pm free vsync/refresh driver Platform Priorities (jet)
2pm Intro to Layout (roc/dbaron) rr & chaos (roc) use of performance tools demo (dbaron) SVG performance work (small group requested by Taiwan based employees) (jwatt) wifi display demo (kenchang)
3pm Selection (roc) competitive & standards landscape (dbaron) XPCOM and String classes (dbaron) (hopefully 4th floor) B2G Layout Discussion (jet)
4pm free Moz2D (small group) Platform Priorities (jet) tbd
5pm Restyle performance patch testing (heycam,vilin,cjku) tbd
6pm Team Dinner tbd

This morning, the Layout team decided to take a walk up to Elephant Mountain near the office. A walk in the park with the Layout team has equal parts of viewing the scenery, and discussing rendering issues for Chinese text (both horizontal and vertical!) It was quite fun.


I’ll post the Platform Graphics team agenda in two weeks after they’re in Taiwan for their work week. Apologies for the use of acronyms and unfamiliar jargon as the Rendering teams often use these terms to describe complex features. Send me a comment if I can help clarify anything.

The Taiwan teams have been very gracious and welcoming as always. See you all again soon!