@mariozechner/pi-tui

Minimal terminal UI framework with differential rendering and synchronized output for flicker-free interactive CLI applications.

Features

• Differential Rendering: Three-strategy rendering system that only updates what changed
• Synchronized Output: Uses CSI 2026 for atomic screen updates (no flicker)
• Bracketed Paste Mode: Handles large pastes correctly with markers for >10 line pastes
• Component-based: Simple Component interface with render() method
• Built-in Components: Text, Input, Editor, Markdown, Loader, SelectList, Spacer, Image, Box, Container
• Inline Images: Renders images in terminals that support Kitty or iTerm2 graphics protocols
• Autocomplete Support: File paths and slash commands

Quick Start

import { TUI, Text, Editor, ProcessTerminal } from "@mariozechner/pi-tui";

// Create terminal
const terminal = new ProcessTerminal();

// Create TUI
const tui = new TUI(terminal);

// Add components
tui.addChild(new Text("Welcome to my app!"));

const editor = new Editor();
editor.onSubmit = (text) => {
    console.log("Submitted:", text);
    tui.addChild(new Text(`You said: ${text}`));
};
tui.addChild(editor);

// Start
tui.start();

Core API

TUI

Main container that manages components and rendering.

const tui = new TUI(terminal);
tui.addChild(component);
tui.removeChild(component);
tui.start();
tui.stop();
tui.requestRender(); // Request a re-render

Component Interface

All components implement:

interface Component {
    render(width: number): string[];
    handleInput?(data: string): void;
}

Built-in Components

Container

Groups child components.

const container = new Container();
container.addChild(component);
container.removeChild(component);

Box

Container that applies padding and background color to all children.

const box = new Box(
    1,                  // paddingX (default: 1)
    1,                  // paddingY (default: 1)
    (text) => chalk.bgGray(text)  // optional background function
);
box.addChild(new Text("Content", 0, 0));
box.setBgFn((text) => chalk.bgBlue(text));  // Change background dynamically

Text

Displays multi-line text with word wrapping and padding.

const text = new Text("Hello World", paddingX, paddingY); // defaults: 1, 1
text.setText("Updated text");

Input

Single-line text input with horizontal scrolling.

const input = new Input();
input.onSubmit = (value) => console.log(value);
input.setValue("initial");

Key Bindings:

• Enter - Submit
• Ctrl+A / Ctrl+E - Line start/end
• Ctrl+W or Option+Backspace - Delete word backwards
• Ctrl+U - Delete to start of line
• Ctrl+K - Delete to end of line
• Arrow keys, Backspace, Delete work as expected

Editor

Multi-line text editor with autocomplete, file completion, and paste handling.

const editor = new Editor();
editor.onSubmit = (text) => console.log(text);
editor.onChange = (text) => console.log("Changed:", text);
editor.disableSubmit = true; // Disable submit temporarily
editor.setAutocompleteProvider(provider);

Features:

• Multi-line editing with word wrap
• Slash command autocomplete (type /)
• File path autocomplete (press Tab)
• Large paste handling (>10 lines creates [paste #1 +50 lines] marker)
• Horizontal lines above/below editor
• Fake cursor rendering (hidden real cursor)

Key Bindings:

• Enter - Submit
• Shift+Enter, Ctrl+Enter, or Alt+Enter - New line (terminal-dependent, Alt+Enter most reliable)
• Tab - Autocomplete
• Ctrl+K - Delete line
• Ctrl+A / Ctrl+E - Line start/end
• Arrow keys, Backspace, Delete work as expected

Markdown

Renders markdown with syntax highlighting and optional background colors.

const md = new Markdown(
    "# Hello\n\nSome **bold** text",
    bgColor,           // optional: "bgRed", "bgBlue", etc.
    fgColor,           // optional: "white", "cyan", etc.
    customBgRgb,       // optional: { r: 52, g: 53, b: 65 }
    paddingX,          // optional: default 1
    paddingY           // optional: default 1
);
md.setText("Updated markdown");

Features:

• Headings, bold, italic, code blocks, lists, links, blockquotes
• Syntax highlighting with chalk
• Optional background colors (including custom RGB)
• Padding support
• Render caching for performance

Loader

Animated loading spinner.

const loader = new Loader(tui, "Loading...");
loader.start();
loader.stop();

SelectList

Interactive selection list with keyboard navigation.

const list = new SelectList([
    { value: "opt1", label: "Option 1", description: "First option" },
    { value: "opt2", label: "Option 2", description: "Second option" },
], 5); // maxVisible

list.onSelect = (item) => console.log("Selected:", item);
list.onCancel = () => console.log("Cancelled");
list.setFilter("opt"); // Filter items

Controls:

• Arrow keys: Navigate
• Enter or Tab: Select
• Escape: Cancel

Spacer

Empty lines for vertical spacing.

const spacer = new Spacer(2); // 2 empty lines (default: 1)

Image

Renders images inline for terminals that support the Kitty graphics protocol (Kitty, Ghostty, WezTerm) or iTerm2 inline images. Falls back to a text placeholder on unsupported terminals.

import { Image } from "@mariozechner/pi-tui";

const image = new Image(
    base64Data,        // base64-encoded image data
    "image/png",       // MIME type
    { fallbackColor: (s) => s },  // theme for fallback text
    { maxWidthCells: 60 }         // optional: limit width
);
tui.addChild(image);

Supported formats: PNG, JPEG, GIF, WebP. Dimensions are parsed from the image headers automatically.

Autocomplete

CombinedAutocompleteProvider

Supports both slash commands and file paths.

import { CombinedAutocompleteProvider } from "@mariozechner/pi-tui";

const provider = new CombinedAutocompleteProvider(
    [
        { name: "help", description: "Show help" },
        { name: "clear", description: "Clear screen" },
        { name: "delete", description: "Delete last message" },
    ],
    process.cwd() // base path for file completion
);

editor.setAutocompleteProvider(provider);

Features:

• Type / to see slash commands
• Press Tab for file path completion
• Works with ~/, ./, ../, and @ prefix
• Filters to attachable files for @ prefix

Differential Rendering

The TUI uses three rendering strategies:

1. First Render: Output all lines without clearing scrollback
2. Width Changed or Change Above Viewport: Clear screen and full re-render
3. Normal Update: Move cursor to first changed line, clear to end, render changed lines

All updates are wrapped in synchronized output (\x1b[?2026h ... \x1b[?2026l) for atomic, flicker-free rendering.

Terminal Interface

The TUI works with any object implementing the Terminal interface:

interface Terminal {
    start(onInput: (data: string) => void, onResize: () => void): void;
    stop(): void;
    write(data: string): void;
    get columns(): number;
    get rows(): number;
    moveBy(lines: number): void;
    hideCursor(): void;
    showCursor(): void;
    clearLine(): void;
    clearFromCursor(): void;
    clearScreen(): void;
}

Built-in implementations:

• ProcessTerminal - Uses process.stdin/stdout
• VirtualTerminal - For testing (uses @xterm/headless)

Example

See test/chat-simple.ts for a complete chat interface example with:

• Markdown messages with custom background colors
• Loading spinner during responses
• Editor with autocomplete and slash commands
• Spacers between messages

Run it:

npx tsx test/chat-simple.ts

Development

# Install dependencies (from monorepo root)
npm install

# Run type checking
npm run check

# Run the demo
npx tsx test/chat-simple.ts