Overview

Spool is a cross-platform (Windows + Linux) game library and save-management wrapper built with Tauri 2 (Rust backend) and SvelteKit 5 (frontend).

It maintains a persistent game library with cover art (via SteamGridDB), launches games directly — restoring saves before launch and backing them up on exit — and handles cloud-save sync and conflict detection via ludusavi + bundled rclone. On Linux it launches Windows .exe games through Proton (umu-launcher).

The core idea

A single long-lived Tauri process owns all persistence, subprocess orchestration, OS integration, HTTP clients, and workflow state. The SvelteKit frontend is purely a view onto that state — every file IO, subprocess call, and HTTP request lives in Rust.

Tray-resident lifecycle

Spool runs as one long-lived process. The library window is a view on it — closing the window hides it to the system tray rather than quitting. Quit is only via the tray menu’s “Quit Spool” item. Secondary spool invocations (from Steam shortcuts / Armoury Crate launchers) are caught by tauri-plugin-single-instance and forwarded as argv to the running primary — so there’s no cold-start cost on game launch.

The two halves

• Rust backend — tauri/src-tauri/src/. Persistence, external integrations (ludusavi, SteamGridDB, Steam, sync server), LAN sharing, platform-specific OS integration, and the run-workflow state machine.
• SvelteKit frontend — tauri/src/. Routes (library, add, edit, splash, settings) plus shared lib/ code, including the single typed api.ts IPC wrapper.

Key patterns

• Per-concern Tauri State<T> — commands declare their dependencies as parameters (library: State<'_, SharedLibrary>, etc.). No god object.
• Atomic JSON saves — write to a temp file, then rename over the target, rotating a .bak. Survives a crash mid-write.
• AppHandle::emit cross-window broadcast — events go to all open webviews, so a popup mutating the library refreshes the main window for free.
• RAII run-lock — runner.rs holds a single-launch guard whose Drop releases the slot, even on panic.

Data files

State lives under paths::app_data_dir() — %LOCALAPPDATA%\Spool\ on Windows, ~/.local/share/Spool/ on Linux.

File	Contents
config.json	App-wide settings (binary paths, Proton, cloud-save/rclone, SteamGridDB, UI mode, LAN, sync server)
library.json	The game library — a list of GameEntry objects
covers/	Downloaded SteamGridDB cover images
launchers/	Generated per-game .exe launcher stubs (Windows)
lan-games/	Default install root for games downloaded from LAN peers
prefixes/	Per-game Proton/Wine prefixes (Linux)
debug.log	App log