In terms of our actual data structures and algorithms, we're already starting to be in really good shape. We've dropped a number of components of our core TextBuffer to C++, ensured that most of our algorithms scale logarithmically with file size, cursor count, etc, and made use of native threading for important operations.
1. The one remaining structure that we need to drop to C++ is what we call the 'display index' - the thing that stores the locations of things like folds and soft wraps. Once we do that, opening large files (which is already reasonably fast) will be like butter.
2. Our find-and-replace is already pretty good - you can type without almost any lag even when we're storing the locations of millions of search results. But now that we have the ability to easily use background threads, there are some easy optimizations we could do there. The search results could really update instantaneously, we no longer need to wait until you pause when typing in the search box.
3. We have in the works a major change to our syntax highlighting system using my incremental parsing library Tree-sitter. Once this lands, it should eliminate any perceived latency in syntax highlighting (as well as enable a host of great syntax-related improvements).
4. Atom still uses synchronous IO (which blocks the UI thread) in some places. This is because it was created before GitHub created Electron, so node APIs were not available from the outset. Many of these have been eliminated, but there are several Git-related code paths that we still have not updated. This probably kills the experience of editing on remote drives like SSHFS for some users. We need to revisit these code paths.
Great work with Atom editor. I successfully conviced my friends to move from VSC to Atom on macOS.
It'll probably take a while before there's no more CoffeeScript in the entire Atom org. We're gradually converting the code to JS as we come upon it for other reasons.