Not only does the editor need to track project folders and open files, even something seemingly simple like syntax highlighting can be surprisingly complex[0]. The editor needs to be able to read your inputs (mouse and keyboard) and represent those changes onscreen just like every other piece of software. It needs to repaint the screen with your changes and, depending on the complexity of the editor, load and implement a host of features (auto-complete? bracket matching? code indentation? code standards a la pep8? updates to source control?), with every single keypress and ideally in a matter of milliseconds. All of that takes memory and different editors make different sacrifices.

Of course the extent to which this happens is the whole reason there are different editors. If all you want to do is write text with zero features, then speed isn't an issue at all and you can just write directly in your terminal to a single file with pico or something.

[0] https://code.visualstudio.com/blogs/2017/02/08/syntax-highli...

Slow software is frustrating. A text editor is a tool, it should help and not hinder.

There are a lot of factors that play into the speed (perceived and real) of an editor. Sublime is written in C, which is generally recognized as a performant language when used correctly. In contrast, Atom and VS Code are Electron[1] apps, which mean they have to deal with browser optimization. They both use a lot of tricks[2] to operate as quickly as they do. And in all editors, one bad extension can kill performance, from my recent experience Resharper in Visual Studio increases startup time by 3x.

An editor is not as simple as displaying lines of text a la Notepad, different editors optimize for different use cases.

1. https://electron.atom.io/

2. http://blog.atom.io/2017/06/22/a-new-approach-to-text-render...

The same reason its annoying when any other kind of program is slow, especially interactive ones.

I don't want to see freezes for 2-3 seconds for some GC run, I don't want the letters to appear several 100ms after I've typed, I don't want to wait minutes for it to parse a large-ish file or update the autocomplete suggestions.

https://pavelfatin.com/typing-with-pleasure/

You mean why some editors are slow or why I care?

Not sure about the first.

I care about speed because I like to use "large" files. I prefer a few large files to many small files.

Try using something like xcode or a jetbrains IDE with a large codebase (for the record I like jetbrains software, but it can be slow comparatively).

edit: not sure I correctly understood the parent

Having tried Atom, it's the main reason I stuck with Sublime. Somehow, even typing was slow in some larger files...

It matters for huge files