What kind of rendering engine and why Zed has to build it?

not sure, they do something with the GPU for sure, and because how are you going to draw anything on a monitor or screen without a rendering engine? Surely in their code base they have multiple levels of abstraction for rendering, drawing, and layout in their code base. You can see these kinds of things in other comments here and on their github without reading code.

The browser engine is itself an abstraction point that many people find agreeable on both sides, for those of us that don't have a problem with chromium/codium/electron as a technology, seeing it more so as useful and enabling

In my mind, sharing a common engine across chromium/codium/electron is like how so many things use the linux kernel. To me, the more eyes, devs, and consumers of the code makes it better in the long run

Yes, the thing is, the browser is an extremely expensive abstraction layer. It's like having a car factory where everything is built by general purpose robots - it's very versatile, but obviously if you build an assembly line using dedicated machinery, it's going to run much faster.

But you also have to build your own factory and assembly line, which isn't faster to begin with and takes a lot of effort to get their. Zed still has issues with basics like font rendering and GPU usage from excessive redraws / repaints

Meanwhile, chromium works reasonable well on billions of devices of all shapes and kinds

This is why Electron is so popular. Building entire factory is very expensive.