Depends on what you call “similar”. They’ll have storage, layout, a part of the layout that’s visible, etc, but they may not separate them that clearly, and won’t have that rich an API. TextView is way more flexible than what the typical _text_ editor needs. Text editors typically don’t need multiple fonts, multiple font sizes, varying line spacing, paragraph indents, proportional fonts, right-aligning or decimal tabs, images inside text, etc.

All those features make TextView relatively slow and memory hungry. Because of that, I don’t think _text_ editors that handle multi-megabyte files will use a single NSAttributedString to store the entire document’s text.

Yep. TextView is a beast.

For multi-megabyte files I always use Sublime.

And for multi-gigabyte files I use HexFiend.

BBEdit is more Mac-like than Sublime and handles multi-gig files with ease.

Indeed, there are a handful of those dev-oriented editors that crunch through mega files with ease. No idea why I prefer Sublime. :D

A quick glance at https://github.com/textmate/textmate says they don't but someone correct me if I'm wrong

That depends on the extent on which they rely on the system-provided frameworks. When the needs of the editor get specialized enough, all sorts of hackery happens.

Using CodeMirror in a desktop app seems like an interesting choice. I'd love to hear more about why they took this approach.

Web tech is an obvious pragmatic choice. Cross-platform by default, amazing libraries with great support.

The average user does not care.

A great example of a very different approach to this is Runestone

https://github.com/simonbs/Runestone