yoxterm #

yoxterm is a high-performance terminal emulator for Flutter — a performance-focused fork of xterm.dart (MIT, © xuty). It keeps the upstream API and feature set (VT100/xterm emulation, CJK & emoji, IME, shortcuts, mobile and desktop) and rebuilds the hot paths: parsing, painting and scrolling.

Requires Flutter >= 3.33.0

Why yoxterm over xterm.dart #

Measured by flutter test test/src/ui/perf_benchmark_test.dart and test/src/ui/draw_ops_bench_test.dart, plus AOT microbenchmarks in script/benchmark.dart (Apple Silicon; absolute numbers are machine-dependent, the deltas are not):

What changed under the hood:

• Byte-level input path — Terminal.writeBytes(Uint8List) decodes UTF-8 inline with cross-chunk carry (split multibyte sequences parse once), the escape parser is a persistent state machine with no rollback re-parse, and clean ASCII chunks reach the buffer zero-copy.
• Synchronized output (DEC mode 2026) — BSU/ESU-wrapped TUI frames (neovim, btop, helix, bubbletea) produce exactly one repaint per frame instead of one per PTY chunk; a 150 ms failsafe aborts stalled syncs.
• Glyph-atlas renderer — glyphs are rasterized once into a texture atlas and emitted as batched drawRawAtlas sprite calls instead of one Paragraph per text run. Missing glyphs are collected across the whole frame and the atlas is rebuilt at most once per frame. Box-drawing characters are painted procedurally.
• Pooled paint ops — per-line paint operations are recorded once and replayed for unchanged lines; evicted ops are recycled through an object pool (XRecycler-style) instead of being re-allocated every frame.
• Parser bypass fast path — plain-text chunks without control characters skip the escape parser entirely; scrollback lines are recycled rather than re-allocated, and line resets only touch the occupied prefix (alacritty-style high-water mark).
• Listener fast paths — observable terminal notifications avoid allocation and iteration overhead when nothing is subscribed.
• Output paint throttle — painting is capped at display refresh instead of repainting on every PTY read, so a 120 Hz ProMotion display does not double the paint work.
• Quality ratchet — CI and a pre-commit hook enforce flutter analyze, the full test suite (~1400 tests) and a crap4dart CRAP gate (threshold 61, current max 59) so performance debt cannot grow back.

Screenshots #

Features #

• 📦 Works out of the box — no special configuration required.
• 🚀 Fast — glyph-atlas rendering, pooled paint ops, parser fast paths.
• 😀 Wide character support — CJK and emojis.
• ✂️ Customizable — themes, terminal text style, shortcuts.
• ✔ Frontend independent — the terminal core works without the Flutter frontend (headless testing, server-side emulation).
• 📱 Mobile and desktop — IME integration, keyboard shortcuts, pointer input.

Getting started #

1. Add the dependency:

dependencies:
  yoxterm: ^4.0.0

2. Create the terminal:

import 'package:yoxterm/xterm.dart';

terminal = Terminal();

terminal.onOutput = (output) {
  print('output: $output');
};

3. Attach a view:

child: TerminalView(terminal),

4. Write to the terminal:

terminal.write('Hello, world!');

Done!

More examples #

• A simple terminal in ~100 lines of code: https://github.com/IstiN/yoxterm/blob/main/example/lib/main.dart

• An SSH client in ~100 lines of code with dartssh2: https://github.com/IstiN/yoxterm/blob/main/example/lib/ssh.dart

  

yoxterm powers the terminal panels of YoLoIT, a CLI-first desktop workspace — that is where the performance work originates.

Contributing #

Feature requests and bugs: issue tracker.

Development setup:

git config core.hooksPath scripts   # enables the pre-commit gate
flutter test
flutter test test/src/ui/perf_benchmark_test.dart  # throughput numbers

The pre-commit hook runs flutter analyze, flutter test --coverage and the crap4dart CRAP ratchet. If a change legitimately improves the max CRAP score, lower the threshold in crap4dart.yaml — never raise it to make a regression pass.

License #

MIT. Based on xterm.dart by xuty and the TerminalStudio contributors.