I see a GIF of someone going deleting a couple lines of code, with a meter showing that the application is maintaining 60 FPS. Was this not something Atom could do before? It seems to me that the bare minimum should be maintaining 60 FPS while performing basic editing tasks…is there some nuance here I'm missing?
In a single-threaded setup, maintaining 60fps is likely impossible. You may think of "just deleting a few lines of code" as trivial. But syntax highlighting alone requires re-parsing, as will automated formatting, type inference, and whatever else we expect today. It's unlikely for this to be done within the 16ms frame budget.
If you're offloading such work to separate threads, you can draw the frame right away and maintain 60fps. But you won't be able to update all the meta-information and frequently see "flashes of unstyled code".