systemless

Systemless is a high-level runtime for 68k classic Macintosh applications and games, written in Rust.

It interprets guest 68k code with the m68k crate and handles Mac OS A-line traps in native Rust. That lets packaged Mac applications run without a Mac ROM image, a full System install, or hardware emulation.

Marathon	Escape Velocity

Status

Systemless is focused on real 68k applications that use the classic Mac Toolbox. The HLE now covers the major runtime surfaces needed by interactive software:

• Memory Manager handles, pointers, zones, low-memory globals, and common exception paths.
• Resource Manager, Segment Loader, File Manager calls, and an in-memory HFS-like VFS with data and resource forks.
• QuickDraw ports, regions, text, shapes, PICT, CopyBits, color tables, offscreen GWorlds, cursors, and 1bpp/8bpp framebuffers.
• Event, Menu, Window, Control, Dialog, TextEdit, Cursor, Process, Sound, SANE, and common Toolbox utility traps.
• Sound Manager playback, channel state, command queues, callbacks, file playback, and host audio mixing.

It is not a bit-perfect Mac hardware emulator. Hardware-specific services such as slot interrupts, device queues, removable-media behavior, and multi-process system integration are modeled only where guest-visible behavior matters.

Quick Start

cargo install systemless
systemless path/to/app-or-game.sit

The installed systemless command opens a window, renders the guest framebuffer, maps keyboard and mouse input, and enables audio when a host backend is available.

Common runner options:

systemless --headless --max-instructions 5000000 path/to/app.sit
systemless --arrows-as-numpad path/to/game.sit
systemless --show-menu-bar path/to/app.sit
systemless --cpu-mhz 25 path/to/app.sit

Systemless accepts StuffIt archives, MacBinary files, and raw/macOS resource forks. Archives may contain multiple files; Systemless populates the in-memory VFS and selects an executable resource fork from the archive.

Systemless does not ship applications, games, Mac ROMs, or Apple system software. Use legally obtained application archives.

For a local checkout, use cargo run --release -- path/to/app-or-game.sit.

Library Use

Programmatic loading goes through FixtureRunner:

use systemless::runner::{FixtureRunner, FixtureRunnerConfig};

let bytes = std::fs::read("game.sit").expect("read game");
let mut runner = FixtureRunner::new(32 * 1024 * 1024, FixtureRunnerConfig::default());

systemless::game::load_game(&mut runner, &bytes).expect("load game");
let (_steps, _still_running) = runner.run_steps(100_000, None);
runner.composite_frame();

Use systemless::display to render the current framebuffer for custom frontends.

Crate Map

Build And Test

cargo build --release
cargo test --lib
cargo check --no-default-features
cargo package

The default gui feature enables the desktop runner dependencies: winit, softbuffer, and cpal. Disable default features for headless library builds.

Font Data

Systemless does not load TTF files at runtime. The built-in DejaVu-derived glyph bitmaps are generated into src/quickdraw/fonts/baked.rs and compiled into the crate, so an installed systemless binary can render text without external font files.

The TTF files under assets/fonts/ are source assets for regenerating the baked catalogue. If SYSTEMLESS_ORIGINAL_FONTS_DIR is set, Systemless can also load locally generated bitmap override blobs ahead of the baked catalogue.

Useful Environment Variables

References

Trap implementations cite Inside Macintosh, BasiliskII observations, or fixture contracts where that context is useful. The implementation favors guest-visible behavior over cycle or hardware fidelity.

License

GPL-3.0-or-later. See LICENSE.

Bundled DejaVu font assets are covered by their own license in assets/fonts/LICENSE.DejaVu.txt.