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.
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 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:
$FIREFOX -profile gaia-profile --no-remote app://sms.gaiamobile.org
The Gaia profile lets you use URL’s like app://sms.gaiamobile.org 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://communications.gaiamobile.org
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!