$ cat project.md

Swift Launcher

A Rust desktop Minecraft launcher for fast instance management, mod discovery, live launch diagnostics, and multi-provider authentication.

rustminecraftlauncherlinuxwindows
repo

Overview

Swift Launcher is a native desktop launcher built around a high-density, dark interface for managing Minecraft instances and modded setups. It is written in Rust with Iced, uses asynchronous workers for downloads and launch preparation, and keeps the UI responsive while large asset checks, mod installs, and process logs run in the background.

The project is currently in active alpha. Core flows work, but packaging, provider edge cases, and full release hardening are still moving.

Highlights

  • Native Iced UI with hardware-accelerated rendering through wgpu.
  • Instance dashboard with recent instances, system status, activity, and quick launch controls.
  • Instance management with create, import, export, duplicate, delete, local files, logs, settings, worlds, and servers.
  • Built-in discovery for Modrinth and CurseForge content.
  • Resource install targets for mods, modpacks, resource packs, and shaders.
  • Local mod management with enabled state, categories, dependency grouping, icons, and metadata dedupe.
  • Modpack support for Modrinth .mrpack, CurseForge zips, and Prism/MultiMC imports.
  • Authentication for Microsoft, Ely.by, and LittleSkin.
  • Authlib Injector integration for Ely.by and LittleSkin launches.
  • Managed Java detection/download plus custom Java path and JVM argument support.
  • Live launch logs with severity coloring and crash report capture.
  • World and server cards with quick play actions.
  • Settings for Java, game directory, crash reporter, Discord Rich Presence, and CurseForge API key.

Design Direction

Swift uses an "Obsidian Kinetic" desktop style:

  • deep charcoal surfaces
  • high-contrast typography
  • compact navigation
  • accent color from the Swift lightning mark
  • dense layouts designed for repeated use, not marketing pages

The UI is optimized for desktop players managing multiple modded instances, not for a simplified mobile-like workflow.

Tech Stack

Area Crates
UI iced, wgpu through Iced, image
Async tokio
Minecraft core lighty-core, lighty-version, lighty-auth
Network reqwest with rustls-tls
Storage sled, TOML/JSON via serde
Integrity sha1, ring
Archives zip, tar, flate2
Diagnostics tracing, tracing-subscriber

Supported Content

Content type Status
Vanilla instances Supported
Fabric instances Supported
Quilt instances Supported
Forge / NeoForge instances Present in UI, installer coverage still evolving
Modrinth mods Supported
Modrinth modpacks Supported
Modrinth resource packs Supported
Modrinth shaders Supported
CurseForge browsing/install Supported with API key
CurseForge modpack import Supported with API key
Prism / MultiMC import Supported
Swift zip import/export Supported

Authentication

Swift supports three account providers:

  • Microsoft account device login
  • Ely.by Yggdrasil login
  • LittleSkin Yggdrasil login

Microsoft auth uses an Azure public-client app ID. New Microsoft Java Edition API integrations may require Mojang review/allowlisting. Ely.by and LittleSkin launches use Authlib Injector so game sessions resolve through the selected Yggdrasil provider.

Requirements

  • Rust stable toolchain
  • Linux or Windows desktop environment
  • A working GPU driver for Iced/wgpu rendering
  • Network access for Minecraft metadata, assets, libraries, auth, and content providers
  • Java can be auto-managed by the launcher, but a local Java install also works

Build

cargo build

Release build:

cargo build --release

Windows cross-build from Linux:

cargo build --release --target x86_64-pc-windows-gnu

Run

cargo run

Logging uses tracing_subscriber and honors RUST_LOG.

RUST_LOG=swift_launcher=debug,warn cargo run

Default log filter:

swift_launcher=info,warn

Test

cargo test

In restricted sandboxes, some tests need local sockets and writable temp directories. Run tests outside the sandbox if you see PermissionDenied or read-only filesystem errors from test servers/temp paths.

Runtime Data

Swift stores launcher data in the platform application data directory:

Platform Directory
Linux ~/.local/share/swift-launcher/
Windows %APPDATA%\swift-launcher\
macOS ~/Library/Application Support/swift-launcher/

Common subdirectories:

  • instances/ for instance folders
  • libraries/ for shared Minecraft libraries
  • .swift/ inside instances for launcher metadata
  • swift-launcher.sled/ for account/settings/index storage

Configuration

Most user-facing configuration is available from Settings. These environment variables are mainly useful for development, CI, or custom builds:

Variable Purpose
SWIFT_LAUNCHER_MS_CLIENT_ID Override Microsoft Azure application client ID
SWIFT_LAUNCHER_CURSEFORGE_API_KEY Bundle or inject CurseForge API key
SWIFT_LAUNCHER_DISCORD_CLIENT_ID Enable Discord Rich Presence integration
SWIFT_LAUNCHER_AUTHLIB_LATEST_URL Override Authlib Injector download URL
SWIFT_LAUNCHER_MODRINTH_BASE Test/override Modrinth API base
SWIFT_LAUNCHER_CURSEFORGE_BASE Test/override CurseForge API base
SWIFT_LAUNCHER_ELYBY_BASE Test/override Ely.by auth base
SWIFT_LAUNCHER_LITTLESKIN_BASE Test/override LittleSkin auth base

CurseForge API keys can also be pasted directly in Settings. Players should not need shell exports for normal use.

Project Layout

src/
  main.rs                 Application entrypoint and Iced window setup
  app.rs                  Root state, update loop, subscriptions, async task wiring
  messages.rs             Message enum for UI and background events
  theme.rs                Shared theme, widget styles, color tokens
  screens/                Home, login, settings, loading, instance detail UI
  auth/                   Microsoft, Ely.by, LittleSkin session flows
  instances/              Instance CRUD, install, launch, mods, worlds, archives
  download/               Streaming download jobs and integrity checks
  storage/                Sled-backed account/settings persistence
  system.rs               System status sampling
assets/
  logo.svg
  preview.png
  icons/
  auth/
  images/

Development Notes

  • Do not block the Iced update loop. File I/O, network requests, installs, and launch prep should run through Task, Subscription, or Tokio workers.
  • Keep persistent state in storage/ and UI state in SwiftLauncher.
  • Keep provider-specific logic inside auth/, instances/mods.rs, or instances/archive.rs.
  • Prefer metadata-based resource dedupe over filename-only checks. Mod files often change names across provider versions.
  • Run cargo fmt, cargo test, and cargo clippy --all-targets -- -D warnings before shipping changes.

Current Limitations

  • Forge and NeoForge support is not yet as complete as Fabric/Quilt.
  • Discord Rich Presence IPC is currently Linux-focused.
  • Microsoft Java Edition API access can depend on Mojang review of the Azure application ID.
  • CurseForge modpack resolution requires an API key.
  • The launcher is alpha software; expect provider edge cases while install and import logic matures.

Legal

Swift Launcher is not affiliated with Microsoft, Mojang Studios, Modrinth, CurseForge, Ely.by, or LittleSkin. Minecraft assets, libraries, accounts, and services remain owned by their respective rights holders. Use this launcher in accordance with the Minecraft EULA, Microsoft account terms, and provider API terms.

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