OffscreenCanvas, jobs, life

Hoo boy, it’s been a long time since I last blogged… About 2 and a half years! So, what’s been happening in that time? This will be a long one, so if you’re only interested in a part of it (and who could blame you), I’ve titled each section.

Leaving Impossible

Well, unfortunately my work with Impossible ended, as we essentially ran out of funding. That’s really a shame, we worked on some really cool, open-source stuff, and we’ve definitely seen similar innovations in the field since we stopped working on it. We took a short break (during which we also, unsuccessfully, searched for further funding), after which Rob started working on a cool, related project of his own that you should check out, and I, being a bit less brave, starting seeking out a new job. I did consider becoming a full-time musician, but business wasn’t picking up as quickly as I’d hoped it might in that down-time, and with hindsight, I’m glad I didn’t (Covid-19 and all).

I interviewed with a few places, which was certainly an eye-opening experience. The last ‘real’ job interview I did was for Mozilla in 2011, which consisted mainly of talking with engineers that worked there, and working through a few whiteboard problems. Being a young, eager coder at the time, this didn’t really phase me back then. Turns out either the questions have evolved or I’m just not quite as sharp as I used to be in that very particular environment. The one interview I had that involved whiteboard coding was a very mixed bag. It seemed a mix of two types of questions; those that are easy to answer (but unless you’re in the habit of writing very quickly on a whiteboard, slow to write down) and those that were pretty impossible to answer without specific preparation. Perhaps this was the fault of recruiters, but you might hope that interviews would be catered somewhat to the person you’re interviewing, or the work they might actually be doing, neither of which seemed to be the case? Unsurprisingly, I didn’t get past that interview, but in retrospect I’m also glad I didn’t. Igalia’s interview process was much more humane, and involved mostly discussions about actual work I’ve done, hypothetical situations and ethics. They were very long discussions, mind, but I’m very glad that they were happy to hire me, and that I didn’t entertain different possibilities. If you aren’t already familiar with Igalia, I’d highly recommend having a read about them/us. I’ve been there a year now, and the feeling is quite similar to when I first joined Mozilla, but I believe with Igalia’s structure, this is likely to stay a happier and safer environment. Not that I mean to knock Mozilla, especially now, but anyone that has worked there will likely admit that along with the giddy highs, there are also some unfortunate lows.

Igalia

I joined Igalia as part of the team that works on WebKit, and that’s what I’ve been doing since. It almost makes perfect sense in a way. Surprisingly, although I’ve spent overwhelmingly more time on Gecko, I did actually work with WebKit first while at OpenedHand, and for a short period at Intel. While celebrating my first commit to WebKit, I did actually discover it wasn’t my first commit at all, but I’d contributed a small embedding-related fix-up in 2008. So it’s nice to have come full-circle! My first work at Igalia was fixing up some patches that Žan Doberšek had prototyped to allow direct display of YUV video data via pixel shaders. Later on, I was also pleased to extend that work somewhat by fixing some vc3 driver bugs and GStreamer bugs, to allow for hardware decoding of YUV video on Raspberry Pi 3b (this, I believe, is all upstream at this point). WebKit Gtk and WPE WebKit may be the only Linux browser backends that leverage this pipeline, allowing for 1080p30 video playback on a Pi3b. There are other issues making this less useful than you might think, but either way, it’s a nice first achievement.

OffscreenCanvas

After that introduction, I was pointed at what could be fairly described as my main project, OffscreenCanvas. This was also a continuation of Žan’s work (he’s prolific!), though there has been significant original work since. This might be the part of this post that people find most interesting or relevant, but having not blogged in over 2 years, I can’t be blamed for waffling just a little. OffscreenCanvas is a relatively new web standard that allows the use of canvas API disconnected from the DOM, and within Workers. It also makes some provisions for asynchronously updated rendering, allowing canvas updates in Workers to bypass the main thread entirely and thus not be blocked by long-running processes on that thread. The most obvious use-case for this, and I think the most practical, is essentially non-blocking rendering of generated content. This is extremely handy for maps, for example. There are some other nice use-cases for this as well – you can, for example, show loading indicators that don’t stop animating while performing complex DOM manipulation, or procedurally generate textures for games, asynchronously. Any situation where you might want to do some long-running image processing without blocking the main thread (image editing also springs to mind).

Currently, the only complete implementation is within Blink. Gecko has a partial implementation that only supports WebGL contexts (and last time I tried, crashed the browser on creation…), but as far as I know, that’s it. I’ve been working on this, with encouragement and cooperation from Apple, on and off for the past year. In fact, as of August 12th, it’s even partially usable, though there is still a fair bit missing. I’ve been concentrating on the 2d context use-case, as I think it’s by far the most useful part of the standard. It’s at the point where it’s mostly usable, minus text rendering and minus some edge-case colour parsing. Asynchronous updates are also not yet supported, though I believe that’s fairly close for Linux. OffscreenCanvas is enabled with experimental features, for those that want to try it out.

My next goal, after asynchronous updates on Linux, is to enable WebGL context support. I believe these aren’t particularly tough goals, given where it is now, so hopefully they’ll happen by the end of the year. Text rendering is a much harder problem, but I hope that between us at Igalia and the excellent engineers at Apple, we can come up with a plan for it. The difficulty is that both styling and font loading/caching were written with the assumption that they’d run on just one thread, and that that thread would be the main thread. A very reasonable assumption in a pre-Worker and pre-many-core-CPU world of course, but increasingly less so now, and very awkward for this particular piece of work. Hopefully we’ll persevere though, this is a pretty cool technology, and I’d love to contribute to it being feasible to use widely, and lessen the gap between native and the web.

And that’s it from me. Lots of non-work related stuff has happened in the time since I last posted, but I’m keeping this post tech-related. If you want to hear more of my nonsense, I tend to post on Twitter a bit more often these days. See you in another couple of years 🙂

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