I recently launched a text editor for iOS that uses TextKit 2 and is highly performant with files of 5,000 lines (I tested with Moby Dick from Project Gutenberg). I made it between Aug 2025 and Apr 2026, development is ongoing.

Every keystroke is restyled in under 8ms: no debouncing, no delayed rendering. 20 rapid keystrokes are processed in 150ms with full restyling after each one.

Tag and boolean searches complete in under 20ms. Visible-range rendering is 25x faster than full-document styling. 120Hz screen refresh supported.

App file size was 722 KB for 1.0, and 1.1 with more features is looking like ~950 KB.

If I can do it on iOS then it's must be 10x easier on macOS.

https://www.gingerbeardman.com/apps/papertrail/

Having worked on an interactive novel in 2012 (NSString and attributes), low level glyphs (API deprecated) on a rogue-like, two chat apps (with markdown support for formatting) in SwiftUI, and an idle game using a mix of iOS tricks but all wrapped in SwiftUI.. I’m going to agree with how I summarized this response: skill issue.

It's likely the SwiftUI Mac implementation is subpar. SwiftUI-on-Catalyst might be a better choice for these applications, but it probably has other problems.

> If I can do it on iOS then it's must be 10x easier on macOS.

I strongly doubt this. I suspect it's the exact opposite situation. But I'd like to hear from someone who knows.

So sounds like a skill issue by the author then.