Nilac Text Editor

Nilac Text Editor is a minimal terminal-based text editor written in Python from scratch. It focuses on demonstrating editor internals such as mutable text buffer management, cursor and viewport state, manual terminal rendering, undo/redo using reversible operations, search highlighting, replace-all behavior, and file loading/saving.

This is a portfolio and educational project, not a production editor or a package intended for public distribution.

Demo

The repository includes GIF demos showing the editor's core behavior:

• Typing and navigation:
• Undo and redo:
• Search/save workflow:
• Replace-all behavior:

Features

• Mutable line buffer represented as lists of characters.
• Cursor movement across rows, columns, line boundaries, and words.
• Vertical and horizontal viewport scrolling.
• Manual terminal rendering with ANSI cursor movement.
• Undo and redo for reversible edit operations.
• Search result tracking and ANSI highlighting.
• Replace-all support with undo integration.
• Basic file open, save, new-file, and last-file restore behavior.

Why This Project Matters

Text editors hide a surprising amount of state management behind simple interactions. This project keeps those mechanics visible by implementing the core behavior directly instead of relying on curses, GUI frameworks, or editor widgets.

Architecture Overview

The editor is split into two main modules:

• buffer_op.py owns the mutable text buffer, cursor position, viewport offsets, search matches, and undo/redo stacks.
• main.py owns the terminal event loop, rendering, prompts, hotkeys, and file workflow.

Text is stored as a list of lines, where each line is a list of characters. Editing actions are represented as operation dictionaries, then applied through a central dispatcher so undo and redo can reverse or replay the same logical changes.

See docs/architecture.md for a fuller explanation of the design.

Running Locally

Requirements:

• Python 3.10+
• keyboard

Install dependencies:

pip install -r requirements.txt

Run the editor:

python main.py

On Windows, run.bat is also included as a convenience launcher.

Controls

Control	Action
Arrow keys	Move cursor
Home / End	Move to start or end of line
Ctrl+Left / Ctrl+Right	Move by word
Page Up / Page Down	Move by viewport page
Ctrl+O	Open file
Ctrl+S	Save file
Ctrl+N	Create a new file
Ctrl+Z	Undo
Ctrl+Y	Redo
Ctrl+/	Search
Ctrl+R	Replace all
Esc	Exit search mode
Ctrl+Q	Save and quit

Testing

The test suite covers core editor behavior such as insert/delete, undo/redo, line split/join, search, replace-all, cursor movement, page navigation, file loading, and buffer reset/clear behavior.

Run tests with:

pytest

Project Structure

.
|-- assets/                 Demo GIFs
|-- docs/                   Project documentation
|-- tests/                  pytest coverage for buffer operations
|-- buffer_op.py            Buffer, cursor, viewport, search, and undo/redo logic
|-- main.py                 Terminal rendering, input loop, hotkeys, and file I/O
|-- requirements.txt        Runtime dependencies
|-- pyproject.toml          Test, formatting, and linting configuration
|-- run.bat                 Windows launcher
|-- LICENSE                 MIT license
`-- README.md              Project overview

Known Limitations

• Uses terminal-specific rendering and input behavior.
• Keyboard/input handling may vary across operating systems.
• The keyboard package may require elevated permissions depending on the OS.
• No mouse support.
• No syntax highlighting.
• No tabs or multiple open files.
• Intended as a portfolio/learning project, not a production editor.

Future Improvements

• Refactor global editor state into an EditorState object.
• Replace dictionary-based operations with typed operation dataclasses.
• Add syntax highlighting.
• Add line numbers.
• Add dirty-state tracking.
• Improve cross-platform input handling.
• Add more tests for edge cases.

License

MIT