GeckoView is a wrapper around Gecko to make it easy to embed it into applications. I heard it's API is similar to WebView, but it's not a complete drop-in replacement.
If you want to know for sure if Webrender is enabled you can go to about:config and check the Graphics section. If Compositing is 'Webrender' it's turned on.
Webrender (the new renderer maxyme was talking about) will move to gfx-rs later on [1]. That allows the renderer to run on Vulkan, DirectX 11 and 12, Metal and OpenGL.
It only works in Firefox Nightly. The flag exists in Beta and Stable, but since Stylo isn't compiled with these versions the flag doesn't actually do anything.
Currently the server doesn't do collision checks with Players, so you wouldn't notice ghost blocks. It does make it allot easier for hackers though.
What makes it a good alternative is that it's reasonably lightweight. We currently have a server running on a RasPi 1 B where people can build structures for the world generator: https://forum.cuberite.org/thread-1372.html
> The old system will still be needed post-WebRender for printing at the very least.
Isn't it possible to take a frame from WebRender and print that? Having two separate systems seems like allot of unnecessary maintenance. Especially if one of those systems is only used on rare occasions like printing.
Currently Quantum CSS (Stylo) and Quantum Render (Webrender) are both in Firefox Nightly, but they are unstable and can cause really bad performance, especially Quantum Render. They won't be done until at least Firefox 57 and some most likely later.
Quantum Compositor is in Release already I believe. It's the out of process compositor for Firefox.
Changes from Quantum Flow are continuing to be implemented into Nightly and later on Beta.
I haven't ready much about the progress around Quantum DOM, and I have no idea for which release it is targeted.
True, Gecko lacks a real API for embedding. Servo on the other hand has embedding in mind from the start. There is someone from the Servo team working on it: https://github.com/paulrouget/servoshell