bettertui_engine

High-performance terminal UI engine written in Rust. The native core of BetterTUI: layout, rendering, text editing, input, animation, terminal emulation, PTY management, font/glyph handling, and syntax highlighting - all in a single dependency.

What it does

Flexbox layout - Taffy-powered layout engine (flexbox and grid semantics)
Rendering - ANSI output pipeline with framebuffer, painter, render passes, and dirty-region diffing so only changed cells are redrawn
Node tree - arena-allocated render tree with generational indices (no borrow-check fights, cheap inserts/removes)
Text editing - rope-backed buffer with undo/redo, search, wrapping, selection, cursor and viewport management
Input - keyboard parsing, mouse events, focus management and traversal, declarative keybindings
Terminal emulation - embedded VT state machine, terminal capability queries, scrollback buffers
PTY management - spawn and drive pseudo-terminals via portable-pty
Animation - timelines, tweens, easing functions
Fonts and glyphs - font loading/metrics plus built-in NerdFont icon registry generated at build time
Syntax highlighting - tree-sitter grammars for JavaScript, TypeScript, Rust, Python, JSON, HTML, CSS, Bash
Scheduling and events - frame scheduler, event bus, emitters, and a composable event pipeline
Theming - light/dark themes with spacing and border tokens

Install

[dependencies]
bettertui_engine = "0.1"

Quick start

Build a small node tree, lay it out, and render one ANSI frame to stdout:

use bettertui_engine::render::Renderer;
use bettertui_engine::taffy::Sizing;
use bettertui_engine::tree::{NodeArena, NodeKind, RenderNode};

fn main() {
    let mut arena = NodeArena::new();

    let root = arena.insert(RenderNode::box_node());
    let label = arena.insert(RenderNode::text("Hello from bettertui_engine"));
    arena.append_child(root, label).unwrap();

    {
        let root_node = arena.get_mut(root).unwrap();
        root_node.layout.width = Some(Sizing::Points(80.0));
        root_node.layout.height = Some(Sizing::Points(24.0));
    }

    let mut renderer = Renderer::new(80, 24);
    let frame = renderer.render(&mut arena);
    print!("{}", String::from_utf8_lossy(&frame.output_data));
}

Feature flags

Feature	Default	Description
`diagnostics`	yes	Render/frame/cache diagnostic counters. Disable with `default-features = false` for zero-overhead release builds.
`napi`	no	Node.js bindings via napi-rs. Only needed when building the `bettertui_engine.node` addon; not used by pure-Rust consumers.
`production`	no	Convenience alias enabling `release-logs-warn`.
`release-logs-off` / `-error` / `-warn` / `-info` / `-debug`	no	Compile-time log gating; statically removes `tracing` events below the chosen level from release builds. Pick at most one.

Modules

Module	Purpose
`tree`	Arena-allocated render tree: nodes, colors, styles, traversal
`taffy`	Layout engine integration, layout props/results, render-tree builder
`render`	Renderer, painter, render passes/pipeline, ANSI backend
`framebuffer`	Cell grid with per-cell attributes
`dirty_diff`	Region diffing between frames for partial redraws
`ansi`	Escape-sequence encoding, clipboard OSC sequences
`text`	Rope buffer, editing, undo, search, wrap, selection, cursor, viewport
`input`	Keys, mouse, focus manager, keybindings
`terminal`	VT state machine, capabilities, queries, screen, scrollback, process glue
`pty`	Pseudo-terminal spawning and IO
`animation`	Timelines, tweens, easing
`event_bus` / `event_emitter` / `event_pipeline`	Event distribution primitives
`font` / `glyph`	Font loading, metrics, glyph rasterization support
`graphics` / `graphics_protocol`	Terminal graphics protocol support
`hit_grid`	Hit testing from mouse coordinates to nodes
`logger`	Filtering, formatting, panic hooks, diagnostics
`plugin`	Plugin host, capabilities, slot registry
`protocol`	Command protocol types
`scheduler`	Frame scheduling and pacing
`span_feed`	Styled span streaming
`syntax`	Tree-sitter based syntax highlighting
`theme`	Theme definitions (light/dark), spacing/border tokens
`clock`	Monotonic time source

Documentation

API reference: https://docs.rs/bettertui_engine
Project home: https://bettertui.dev
Source: https://github.com/localfirstai/bettertui

Ecosystem

bettertui_engine powers BetterTUI. It works standalone in any pure-Rust project, and the same crate compiles into the Node.js addon used by the npm package @bettertui/core when the optional napi feature is enabled.

Minimum supported Rust version

Rust 1.88 (edition 2024).

License

MIT. See LICENSE.

bettertui_engine 0.1.1