$ show LinwoodDev/Butterfly
Butterfly is a cross-platform, open-source note-taking application built with Flutter, offering an infinite canvas for drawing, writing, and organizing notes. It supports a wide range of tools including pen, eraser, shape, text, laser, ruler, stamp, and area management, along with features like layers, pages, waypoints, backgrounds, textures, and real-time collaboration via WebSocket or Swamp protocols. The application can export to PDF, SVG, PNG, and Xournal++ formats, and integrates with WebDAV for file synchronization and backup. It is available on Android, Windows, Linux, macOS, iOS, and web platforms. The architecture follows a BLoC/Cubit pattern for state management, with a clear separation of concerns: handlers manage tool interactions, renderers draw elements on the canvas, and selections provide property editing UIs. The core data models are defined in a separate Dart package (`butterfly_api`) using freezed and json_serializable for immutable, serializable objects. The app uses a custom file system abstraction (`lw_file_system`) to support local, WebDAV, and Android SAF storage backends. Keyboard shortcuts are declaratively defined via an Action/Intent system, and the app supports embedding via a postMessage bridge for iframe integration. Key entry points include `app/lib/main.dart` for app bootstrap, `app/lib/bloc/document_bloc.dart` for central document state, and the various handler and renderer files in `app/lib/handlers/` and `app/lib/renderers/`. The application relies on external dependencies such as Flutter SDK, flutter_bloc, freezed, archive, phosphor_flutter, pdfrx, and material_leap. The codebase is actively maintained with frequent releases, extensive localization (20+ languages), and a comprehensive documentation site built with Astro/Starlight.
The LLM identified 5 files worth highlighting for reuse:
Provides `CoalescedAsyncRunner`, a reusable utility for throttling or debouncing asynchronous tasks. It allows configuring a restart delay and ensures that only the latest invocation is executed, making it ideal for search-as-you-type or auto-save scenarios. The implementation is self-contained and can be extracted into any Dart project.
A reusable Flutter widget for selecting colors, integrated with a palette dialog. It supports both predefined palettes and custom color input, and is used throughout the app for tool and element properties. The widget is decoupled from the application's state management and can be reused in other Flutter projects with minimal adaptation.
A custom input widget for entering aspect ratios, supporting expressions like '√2:1' and colon-separated values. It uses an `ExpansionPanelList` to expose shape detection settings. The widget is self-contained and provides a pattern for parsing and validating non-standard numeric input, making it reusable in any Flutter application requiring aspect ratio configuration.
Defines the abstract `Renderer<T>` base class that all element and background renderers extend. It provides a consistent interface for building to a `Canvas` and to SVG (via `buildSvg`), along with affine transformation support. This pattern enables easy addition of new element types and is a clean example of the strategy pattern applied to rendering. The class is generic and could be extracted as a library for any canvas-based Flutter application.
Implements a declarative keyboard shortcut system using `ShortcutDefinition` objects that map key combinations to `Intent`/`Action` pairs. This pattern centralizes shortcut configuration and allows easy customization. The module is self-contained and demonstrates a clean way to manage keyboard shortcuts in Flutter, reusable in any Flutter application that needs configurable shortcuts.