How to write your browser on the Mozilla Gecko engine?

Question

Mozilla

With WebKit, everything is more or less clear - there are ready-made components for many UI libraries with bindings for many programming languages. With Trident (Internet Explorer) it is more or less the same, adjusted for Windows-only and related technologies (ActiveX, .Net, etc.). But what about Mozilla Gecko? There used to be at least an ActiveX component for Windows, but it seems to have ceased to develop, not to mention the fact that ActiveX imposes its limitations not only in terms of choosing an OS, but also in terms of interaction with the engine.
The task that is spinning in my head is to write an alternative to Firefox with the same engine (because I like it not only to support some features that are missing in WebKit / Blink, but also to provide much more opportunities than the latest to invade the process of its work from the side of extensions), but with an interface and functional binding to my taste, with everything that I need and without everything superfluous that I don’t like about it (unfortunately, I have long ceased to have the ability to customize the original).

Answer 1

We made our own engine for Windows a la "nodejs-webkit", but not on a webkit, but just on Mozilla. For this we used XulrunnerSDK.
https://developer.mozilla.org/en/docs/Gecko_SDK
For me, as an amateur in C ++, the thing is quite complicated. Nevertheless, our programmers managed to do a very useful thing on it.

Answer 2

A long time ago, when Macs were still PPC-ish, I tried to embed FF into a Cocoa widget at the behest of a customer who sent me. It turned out that everything inside is so cunningly woven that it cannot be done in a simple way. From my recollection, FF simply didn't have a good decent separation between the HTML rendering layer and the UI layer. It's probably gotten a little better since then, if not a little worse.