Trevor Whittingham • 6/24/2026

Add TextKit Line Numbers And Foldable Sections Without Rebuilding Text Editing

This article explains how to add line numbers and collapsible sections to a text editor using TextKit 2 without rebuilding the entire text editing system. It advocates for extending existing UITextView and NSTextView behaviors rather than choosing between SwiftUI's limited TextEditor or building a full custom editor. The post covers architecture with SwiftUI as the shell, UIKit for the editing surface, and TextKit for layout, including a gutter view, fold model, and NSTextAttachmentViewProvider reuse. It references WWDC26 sessions and beta-era TextKit 2 APIs for the 2027 SDK cycle.

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#Io #Swift #Textkit