TextBuffer

Text buffer abstractions to power your text editor, in UI or in memory.

Goals

• In-memory text mutations with an API similar to text views.
• Consistent behavior across platforms.

Approach

We operate on the abstraction of a Buffer to perform changes.

This enables usage of the declarative API on multiple buffers at once without having to put the text into a UI component to render.

A NSTextView is a buffer. You can use this declarative API to make changes to text views on screen.

You can also use purely in-memory buffers for text mutations of things you don't want to render. This allows you to read multiple files into buffers in your app and use the declarative API to change their contents, while only rendering a single selected file in a text view.

This is harnessed by DeclarativeTextKit.

Installation

Add TextBuffer as a Swift Package Manager dependency:

dependencies: [
    .package(url: "https://github.com/CleanCocoa/TextBuffer", from: "0.4.0")
]

Key Types

• Buffer — protocol for reading and mutating text with UTF-16 indexed ranges.
• MutableStringBuffer — lightweight in-memory Buffer backed by NSMutableString, for off-screen mutations and tests.
• RopeBuffer — in-memory Buffer backed by TextRope (B-tree rope), for large documents with O(log n) edits.
• NSTextViewBuffer — Buffer conformance for NSTextView, applying changes directly to the text view.
• Undoable — wraps a Buffer with Foundation UndoManager integration for AppKit undo/redo.
• TransferableUndoable — wraps a Buffer with an OperationLog for portable undo history; supports snapshot() and represent(_:) for state transfer.
• OperationLog — value-type undo history that records BufferOperations grouped into UndoGroups. Inspectable via log.history.

Undo

TextBuffer provides two undo wrappers:

• Undoable uses Foundation's UndoManager. Use this when you need AppKit undo/redo integration (e.g., responding to Edit menu actions in an NSTextView-based editor).

• TransferableUndoable uses an OperationLog value type instead. Use this when you need to transfer undo state between buffers — for example, swapping an in-memory buffer's state into a text view. Call snapshot() to capture the current content and undo history, and represent(_:) to restore it into another TransferableUndoable.

License

Copyright © 2025 Christian Tietze. All rights reserved. Distributed under the MIT License.

See the LICENSE file.