The practicality of the case for TenSixFox

After Mozilla's announcement that 10.6-10.8 support is ending, Dan Knight posted two articles on LowEndMac regarding whither a "TenSixFox," both for and against.

TenFourFox gets cited a lot as a successful example of a community-driven Firefox fork (to Tiger PowerPC, for those on our syndicated sites who are unfamiliar), and we're usually what gets pointed to when some open-source project (including Firefox) stops supporting a platform. However, even though we have six years so far of successful ports in the can, we're probably not a great example anymore. While we've had major contributors in the past -- Tobias and Ben in particular, but others as well -- and Chris T still volunteers his time in user support and herds the localizer cats, pretty much all the code and porting work is done entirely by yours truly these days. It's just not the community it was, and it's a lot of work for me personally. Nevertheless, our longevity means the concept of a "TenSixFox" gets brought up periodically with expectations of the same success, as Dan did in his first piece, and as a result a lot of people assume that our kind of lightning will simply strike twice.

Unfortunately, even if you found someone as certifiably insane highly motivated as your humble narrator willing to do it, the tl;dr is that a TenSixFox can't be accomplished in the same way TenFourFox was. Restoring 10.4 compatibility to Firefox is, at the 50,000' level, a matter of "merely" adding back the code Mozilla removed to the widget and graphics modules (primarily between Firefox 3.6 and 4, though older code has been gradually purged since then). The one thing that could have been problematic in the beginning was font support, since Tiger's CoreText is inadequate for handling text runs of the complexity required and the ATSUI support had too many bugs to keep it working, but Mozilla solved that problem for us by embedding a font shaper for its own use (Harfbuzz) which we adopted exclusively. After that, as versions ticked along, whatever new features they introduced that we couldn't support we just ruthlessly disabled (WebGL, WebRTC, asm.js, etc.), but the "core" of the browser, the ability to interpret JavaScript, display HTML and handle basic chrome, continued to function. Electrolysis fundamentally changes all of that by introducing a major, incompatible and (soon to be) mandatory change to the browser's basic architecture. It already has serious issues on 10.6 and there is nothing that says those issues are fixable or avoidable; it may well be impossible to get multi-process operational on Snow Leopard without significant showstoppers. That's not a recipe for continued functionality, and there is no practical way of maintaining single-process support once it disappears because of how pervasive the changes required will eventually be.

Plus, there's another technical problem as well. Currently Firefox can't even be built on 10.6; as of this writing the minimum supported compiler is clang 4.2, which means Xcode 4.6 at minimum, which requires 10.8. This isn't a showstopper yet because cross-building is a viable if inconvenient option, but it makes debugging harder, and since 10.8 is being dropped too it is probable that the Xcode minimum requirement will jump as well.

So if you're that nuts enthusiastic, and you have the chops, what are your options?

Option 1 is to keep using TenFourFox on Rosetta, with all the performance and functionality limitations that would imply. Let me reiterate that I don't support Intel Macs and I still have no plans to; this project is first and foremost for Power Macs. I know some of you do run it on 10.6 for yuks and some of you even do so preferentially, but there's not going to be another Intel build of TenFourFox unless someone wants to do it themselves. That brings us to ...

Option 2 is to build TenFourFox natively for 10.6. I currently only support linking against the 10.4 SDK because of all the problems we had trying to maintain a codebase linkable against 10.4 and 10.5 (Tobias used to do this for AuroraFox but that support is long gone). Fortunately, Xcode 3 will still allow this and you can build and debug directly on a Snow Leopard system; plus, since the system minimum will be 10.6 anyway, you'll dodge issue 209 and you have the option of 10.5 compatibility too. You'll have to get all the MacPorts prerequisites including gcc 4.8, enable the x86 JIT again in JavaScript and deal with some of our big-endian code for fast font table enumeration and a couple other things (the compiler will throw an error so you'll know where to make the changes), but the rest of it should "just work." The downside is that, since you are also linking against the 10.4 SDK (regardless of your declared minimum OS support), you'll also have all the limitations of TenFourFox because you're actually porting it, not Firefox (no WebGL, no plugins, no WebRTC, no CoreText shaper; and, because we use a hybrid of Carbon and Cocoa code, you're limited to a 32-bit build). On the other hand, you'll get access to our security updates and core improvements, which I plan to keep making for as long as I personally use TenFourFox, so certain things will be more advanced than the next option(s), which are ...

Option 3 is to keep building 45ESR for 10.6 after 45ESR support terminates by continuing to port security updates. You won't need to make any changes to the code to get the build off the ground, but you'll need both 10.6 and 10.8 systems to debug and build respectively, and every six weeks you'll have to raid the current ESR branch and backport the changes. You won't get any of the TenFourFox patches and core updates unless you manually add them yourself (and debug them, since we won't support you directly). However, you'll have the option of a 64-bit build and you'll have all the supported 10.6 features as well as support for 10.7 and 10.8.

Finally, option 4 is to keep building firefox-release after 45ESR for 10.6 until it doesn't work anymore. Again, you'll need both 10.6 and 10.8 systems to be effective. This option would get you the most current browser in terms of technology, and even if Electrolysis is currently the default, as long as single-process mode is still available (such as in Safe Mode or for accessibility) you should be able to hack the core to always fall back to it. However, now that 10.6-10.8 support is being dropped, you'll have to undo any checks to prevent building and running on those versions and you might not get many more release cycles before other things break or fail to build. Worst of all, once you get marooned on a particular version between ESRs you'll find backporting security patches harder since you're on a branch that's neither fish nor fowl (from personal experience).

That's about the size of it, and I hope it makes it clear TenFourFox and any putative TenSixFox will exist in very different technological contexts. By the time 45ESR support ends, TenFourFox will have maintained source parity with Firefox for almost seven years and kept up with most of Gecko's major technology advancements, and even the very last G5 to roll off the assembly line will have had 11 years of support. I'm pretty proud of that, and I feel justifiably so. Plus, my commitment to the platform won't end there when we go to feature parity; we'll be keeping a core that can still handle most current sites for at least a couple years to come, because I'll be still using it.

TenSixFox, on the other hand, even if it ends up existing, will lack source parity with Firefox just about from its very beginning. It's not going to be the technological victory that we were at our own inception in 2010, and it's not likely to be the success story we've been for that and other important reasons. That doesn't mean it's not worth it, just that there will be some significant compromises and potential problems, and you'd have to do a substantial amount of work now and in the future to keep it viable. For many of you, that may not be worth it, but for a couple of you, it just might be.