Adding `edit_core` library as a dependency

Run this command in a terminal, in your project's directory:

cargo add edit_core

To add it manually, edit your project's Cargo.toml file and add to the [dependencies] section:

edit_core = "0.2.0"

The edit_core library will be automatically available globally. Read the edit_core library documentation.

Back to the crate overview.

Readme

edit_core

A small, dependency-free text editing core for building a terminal or GUI editor. It models a buffer of lines, a cursor, and a viewport, and applies editing actions (movement, insertion, deletion) while keeping the cursor visible.

Features

Line-oriented buffer with UTF-8 safe, character-based indexing.
Cursor movement across lines with automatic clamping.
UTF-8-aware word movement (MoveWordLeft, MoveWordRight) with consistent token jumps.
Insert, delete, and newline actions.
Viewport scrolling with visible line slicing.
Dirty flag tracking for mutations only.

Usage

use edit_core::{Action, Buffer, Editor, Viewport};

let buffer = Buffer::from_text("hello\nworld");
let viewport = Viewport::new(5, 40);
let mut editor = Editor::new(buffer, viewport);

editor.apply(Action::MoveRight);
editor.apply(Action::Insert('!'));

assert_eq!(editor.buffer().as_text(), "h!ello\nworld");

Public API

Types

Buffer: Stores the text as a vector of lines.
Cursor: Row and column position (character-based).
Viewport: Visible window with row/column offsets and size.
Action: Editing actions (character movement, word movement, insertion, deletion, newline).
Editor: Applies actions to a buffer while managing cursor, viewport, and dirty state.

`Buffer`

Buffer::new() -> Buffer
Buffer::from_text(text: &str) -> Buffer
Buffer::as_text(&self) -> String
Buffer::line(&self, row: usize) -> Option<&str>
Buffer::line_count(&self) -> usize

`Cursor`

Cursor::new(row: usize, col: usize) -> Cursor
Fields: row, col

`Viewport`

Viewport::new(height: usize, width: usize) -> Viewport
Fields: row_offset, col_offset, height, width

`Action`

MoveLeft, MoveRight, MoveWordLeft, MoveWordRight, MoveUp, MoveDown
Insert(char)
DeleteBackward, DeleteForward
Newline

Word movement behavior:

Skip leading whitespace first.
Jump an identifier run [A-Za-z0-9_]+ as one token.
Treat punctuation/symbol characters as single-token jumps.
Cross line boundaries when needed.

`Editor`

Editor::new(buffer: Buffer, viewport: Viewport) -> Editor
Editor::buffer(&self) -> &Buffer
Editor::cursor(&self) -> Cursor
Editor::viewport(&self) -> Viewport
Editor::set_viewport(&mut self, viewport: Viewport)
Editor::is_dirty(&self) -> bool
Editor::reset_dirty(&mut self)
Editor::apply(&mut self, action: Action)
Editor::visible_lines(&self) -> Vec<String>
Editor::cursor_screen_pos(&self) -> (usize, usize)

Notes

Rows and columns are character indices, not byte offsets.
visible_lines returns slices based on the current viewport offsets and size.

Internal Layout

src/lib.rs: Crate wiring and re-exports.
src/types.rs: Public types (Action, Cursor, Viewport).
src/buffer.rs: Line-based text storage.
src/editor.rs: Editing engine and cursor/viewport behavior.
src/text.rs: UTF-8 helper routines for character-safe slicing/indexing.

Adding edit_core library as a dependency

Adding `edit_core` library as a dependency