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Comment by jgraham | Hacker News Reader

Unfortunately the new title seems to be misleading in a different way. There is no "project to replace gecko with servo". There is a project to advance gecko so it is state of the art in browser engines. Much of the current state of the art has been developed in Servo, and the natural way to bring that technology to gecko is to integrate the components from servo directly. This has other nice properties like increasing the Rust-to-C++ ratio, which we believe will be a win for safety and maintainability. But it is nevertheless components, rather than the whole shebang. Servo, for example, only just got document.write support and still (as far as I know) doesn't have a correct representation of document history. So it is some way from being a production grade engine for use on the general web.

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Ok, we've taken another shot at a more accurate title by saying "transitioning" instead of "replacing", as suggested here: https://news.ycombinator.com/item?id=13328415. If anyone suggests a better title, we can change it again.

Well, you can write individual components in Rust and put them into Servo and then refactor the existing C++ to make it modular enough for those components to be replaced by the Rust version.

Then eventually you'll be able to replace enough components that it's all Servo, and no Gecko. At that point Servo will be functionally complete, as its individual components will be on par with the Gecko components.

I think it's unclear whether everything will get replaced by Rust components from Servo: certainly, smaller components are likely to get replaced, but larger interwoven parts are obviously going to be far harder to replace. I suspect not all of the Rust code that replaces the old C++ code will be from Servo: some will be written specifically for Gecko.

Firefox has already committed to eliminating XUL components. Once it has the correct APIs to emulate existing add-ons, mobile Firefox could probably switch over to Servo. Desktop has a lot more cruft and features, so it will probably be harder to switch.

But I wouldn't be surprised if Servo is usable on mobile in 2017.

I would be astonished if Servo is usable as a mass-market web browser in 12 months. Writing a rendering engine is hard because there is quarter of a century of legacy to deal with. By the metric of "can I use this for 100% of my browsing needs" Servo is far from being complete.

Much of Mozilla's "quantum" work is actually about improving C++ code e.g. the Quantum DOM project [1], which is a drive to improve scheduling so that a single background tab, even in the same process, can't jank the tab you are currently using [2]. Importing servo components wholesale simply wouldn't help here because Servo doesn't have a sufficiently complete DOM implementation, and I'm not sure the implementation it has contains all the desired properties.

[1] https://billmccloskey.wordpress.com/2016/10/27/mozillas-quan... [2] I am occasionally taken to refer to this project as "Presto: the good parts"

To put servo into production and let it face attackers would be a profuse test for the viability of the memory safety claims.

Rust is already used in stable Firefox. https://hacks.mozilla.org/2016/07/shipping-rust-in-firefox/

Fx has enough holes already to draw attention away from the Rust modules. >:]

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