$ show Textualize/textual
Textual is a Python terminal user interface (TUI) framework that enables building interactive, visually rich applications inside the terminal. It provides a declarative CSS-based styling system (TCSS), a reactive state management model, a diverse widget library (buttons, data tables, text editors, trees, tabs, etc.), and an asynchronous event-driven architecture. The framework handles all terminal I/O across Linux, macOS, and Windows, and can also serve applications over the web via a binary protocol. Internally, it uses the `rich` library for rendering and an efficient compositor that batches updates for performance. The primary entry point is the `App` class in `src/textual/app.py`, from which users subclass and compose widgets via `compose()` methods. Styling can be embedded as `DEFAULT_CSS` or loaded from external `.tcss` files. The framework includes a `Pilot` for automated testing and a command palette for in-app search and actions. Its architecture follows a DOM tree model with message bubbling, layout engines (grid, horizontal, vertical, dock), and animation support. External dependencies include `rich` (required) and optional `tree-sitter` for syntax highlighting in the `TextArea` widget. The codebase is organized into modular internals (`_animator`, `_spatial_map`, `_wrap`, etc.) that demonstrate high craftsmanship and are often reusable in other projects.
The LLM identified 6 files worth highlighting for reuse:
Implements a reactive attribute system using Python descriptors. `Reactive` and `var` enable automatic UI updates when state changes, with optional watchers (`watch_*`), computed properties (`compute_*`), and validators (`validate_*`). It also supports `mutate_reactive` for batch updates on mutable objects. This module is self-contained, heavily tested, and can be extracted into any Python project needing declarative state management without a framework.
Provides the `Strip` class, an immutable representation of a single terminal line composed of Rich segments. It caches division and crop operations to avoid recomputation, supports alignment, filtering, styling, link handling, and conversion to ANSI output. The design is cleanly isolated and could be reused in any terminal rendering library or tool that needs efficient line-level manipulation.
A grid-based spatial index for 2D regions. It stores widget regions in a 2D grid of cells and supports fast queries for overlapping regions, point location, and rectangle intersection. Uses weak references and deduplication. This is a reusable spatial data structure applicable to any UI framework, game engine, or graphics system requiring efficient spatial lookups.
Resolves fractional unit (fr) allocations in layouts using Python's `Fraction` to avoid floating-point errors. Given a list of fractions, minimum sizes, and total available space, it distributes remaining space proportionally while respecting minimums. This is a clean, standalone function that implements the core of a flexbox-like layout algorithm and can be reused in any layout engine.
Contains 30+ easing functions (sine, quad, cubic, elastic, bounce, etc.) as a dictionary of callables. Each function takes a float t (0.0-1.0) and returns an eased value. The module is self-contained, well-tested, and can be extracted for any animation system needing a rich set of easing curves.
A generic bidirectional mapping (bijection) between keys and values. Maintains two dictionaries for O(1) lookups in both directions and raises an error if a duplicate insertion would break the bijection. A simple, robust data structure reusable in any project needing a two-way mapping.