Vscode is perfectly hackable and open, can you be more specific?

From what I have tried, VS Code doesn't allow access to the DOM or give much of an API to modify the visual layer. This makes it very difficult to draw visualizations on top of the editor. It also does not allow plugins to go beyond the standard tab-document metaphor.

For example, students of mine tried to re-implement Patchworks [1] as a VS Code plugin. Didn't seem feasible. They have been very successful in building it in Atom though. As another example, I tried to make a tool that displays a call graph visualization on top of the editor [2]. But again, this was easy in Atom but I couldn't figure it out in VS Code.

Please point me to any documentation or examples of how to implement features like those.

[1] https://youtu.be/GwcxDZT3pXE

[2] http://web.eecs.utk.edu/~azh/pubs/Henley2018bDissertation.pd... Figure 36

It's quite hackable but not like Atom or Emacs.

You can find some plugins that could make Atom seems completely different, but most of the VSCode image you can find on the internet remains similar.

Just like with Emacs you can rewrite Emacs itself. And all of the changes in Atom do not require restarting, while some of the VSCode plugins require to restart the code editor (but might explain a little bit why VSCode is faster).