xterm3 6.3.1

Maintained Flutter terminal emulator package with fast rendering and broad VT/xterm compatibility.

xterm3

pub.dev/packages/xterm3 · API reference · Changelog · Source

xterm3 is a terminal emulator for Flutter applications, on mobile and desktop. It ships a headless emulation core with no Flutter dependency and a renderer on top of it, so the terminal can be driven — and tested — without a widget tree.

It continues the line that started with xterm from TerminalStudio/xterm.dart and was kept alive as xterm2. The original package is unmaintained, and xterm2 has since diverged far enough — rewritten renderer, reworked buffer and reflow, new input and search paths — that it continues here under its own name. xterm2 users migrate by changing the dependency and the package in imports; the public API is unchanged.

Requires Flutter >= 3.19.0

Performance

Same workloads, same harness, three packages. Every number below is reproducible from script/cross_bench/, which depends on all three at once and drives each through its headless core.dart — so nothing per-package sits in the measured path.

xterm 4.0.0 · xterm2 5.2.0 · xterm3 6.3.0. Grid 170x50, 10000 lines of scrollback, 32 MiB per workload in 8 KiB chunks, AOT-compiled, one package per process, three interleaved rounds. Apple M1 Pro, macOS 26.5.1, Dart 3.12.2.

Write throughput, MiB/s — higher is better:

workload	xterm	xterm2	xterm3	vs xterm
plain ASCII output	15.8	86.6	113.4	7.2x
lines wider than the window	16.6	117.8	135.5	8.2x
SGR-heavy (coloured) output	18.8	60.8	57.4	3.1x
UTF-8 (Turkish)	15.4	14.2	63.5	4.1x
Cyrillic	14.8	5.5	90.4	6.1x
alt-screen TUI redraw	19.2	133.2	139.1	7.2x

Scrollback residency, MiB — 10000 lines of ls -l-shaped output retained at a 170-column window; lower is better:

	xterm	xterm2	xterm3
resident scrollback	85.8	79.3	52.8

Resize reflow, ms — one 170 → 80 → 170 column pair with the scrollback full, rewrapping all 10000 retained lines twice; lower is better:

	xterm	xterm2	xterm3
per resize	10.6	4.7	4.6

Two rows are worth reading honestly rather than as a scoreboard. SGR output is 6% slower than xterm2 — a known price of sizing line storage from what a line actually writes, which is what buys the scrollback row; the alternatives were measured at -22% and -14% elsewhere. And reflow is level with xterm2; the 2.3x there is against xterm, not against the immediate predecessor.

The large gaps are on non-ASCII text, and they are structural: both older packages leave the batched write path at the first accented letter, so a language not written in ASCII never batches at all. xterm2 is slower than xterm on Cyrillic for that reason — the rest of its write path got faster around a per-code-point loop that did not.

Renderer frame times, the workloads behind them, and every change that was measured and rejected are in BENCHMARKS.md. Nothing in this package is accepted on the argument that it ought to be faster.

Screenshots

Every image below is a real frame painted by TerminalView, produced by example/lib/screenshot.dart from PTY recordings in example/assets/screenshots/ — so they can be regenerated rather than retouched. Grid 100x30, Cascadia Mono at 13pt.

Shell — SGR colour, CJK, emoji, combining marks, Cyrillic	htop — block elements and meters, drawn procedurally
vim — full-screen redraw on the alternate screen	Search — every match in the scrollback, one of them active

Features

• 📦 Works out of the box. No special configuration required.
• ✔ Frontend independent. The emulation core runs without Flutter — package:xterm3/core.dart has no dart:ui on any path.
• 😀 Unicode 17. Wide characters, grapheme clusters, emoji sequences, and a batched write path that covers Latin, Greek, Cyrillic and Armenian rather than ASCII alone.
• 🔍 Search. Bounded, Unicode-aware, across soft wraps, with a distinct active match — Terminal.search.
• 🔗 Hyperlinks. OSC 8, plus plain http(s):// and www. text detected in the buffer. Modifier-click on desktop, tap on touch.
• 🎨 Procedural glyphs. Box drawing, blocks, mosaics, Braille and Powerline drawn directly, so they tile without font seams at any cell size.
• 🔤 Ligatures. Opt-in via TerminalStyle(enableLigatures: true) with a ligature-capable font such as Fira Code, JetBrains Mono or Iosevka. A ligature is drawn only where it fills exactly the cells it covers, so the grid never shifts; anything else falls back to per-cell painting.
• 🖱 Mouse reporting. DEC modes 1000/1002/1003 with normal, UTF-8, SGR, SGR-pixel and urxvt encodings; extended buttons, horizontal wheel, and Shift+wheel scrollback that survives an application grabbing the mouse.
• ⌨️ Modern key encoding. Kitty keyboard protocol, fixterms chords, and correct modified arrows, function keys, Enter and Escape.
• 🈂️ IME-aware. Composition is held back until the keyboard commits it, in both delete-detection modes — Turkish and CJK text arrives once, correctly.
• 🧭 Semantic prompts. OSC 133/633 anchors tracked across scrollback and reflow, with shortcuts to jump between them.
• ⏱ Paced writing. PacedTerminalWriter feeds PTY output a frame's worth at a time: a burst drains ~50% slower and stays at 75fps instead of 37.
• 🎛 Runtime theming, synchronized output (DEC 2026), DECSCUSR cursor shapes, focus reporting, and OSC 7 working-directory updates.

Getting Started

1. Add the package from pub.dev:

flutter pub add xterm3

or add it to your package's pubspec.yaml file by hand:

dependencies:
  ...
  xterm3: ^6.3.0

2. Create the terminal:

import 'package:xterm3/xterm.dart';
...
terminal = Terminal();

Listen to user interaction with the terminal by simply adding a onOutput callback:

terminal = Terminal();

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

3. Create the view, attach the terminal to the view:

import 'package:xterm3/flutter.dart';
...
child: TerminalView(terminal),

4. Write something to the terminal:

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

Done!

More examples

• Write a simple terminal in ~100 lines of code: https://github.com/klc/xterm3/blob/master/example/lib/main.dart

• Write a SSH client in ~100 lines of code with dartssh2: https://github.com/klc/xterm3/blob/master/example/lib/ssh.dart

• Regenerate the screenshots above: python3 script/screenshots/record.py, then cd example && flutter run --release -d macos -t lib/screenshot.dart

For the original package history, see TerminalStudio/xterm.dart.

Migrating from xterm2

The public API is unchanged. Three mechanical edits:

• xterm2: ^5.3.0 becomes xterm3: ^6.3.0 in pubspec.yaml.
• package:xterm2/... becomes package:xterm3/... in imports. The entry point keeps its name: import 'package:xterm3/xterm.dart';.
• XTERM2_FUZZ_ROUNDS becomes XTERM3_FUZZ_ROUNDS.

Note the licence change below: xterm2 5.3.0 and earlier are MIT, xterm3 6.0.0 and later are AGPL.

Features and bugs

Please file feature requests and bugs at the issue tracker.

Contributions are always welcome!

License

xterm3 is licensed under the GNU Affero General Public License v3.0 or later (AGPL-3.0-or-later). Linking it into an application makes that application a work covered by the AGPL: if you distribute it, or let users interact with it over a network, you must offer them its complete corresponding source under the same license.

The xterm and xterm2 work this package is derived from is MIT licensed and stays available under those terms; that notice is kept in LICENSE.MIT and NOTICE. Versions up to xterm2 5.3.0 are unaffected by this change — the AGPL applies from xterm3 6.0.0 onward.