Charter ♪

A desktop beatmap editor for SIF2 (Love Live! School Idol Festival 2) custom songs, built with Tauri + Rust and a dependency-free vanilla-TypeScript frontend.

Talks to an ew custom-songs server: log in with your user ID + transfer password, chart locally, then upload / manage visibility / browse / download other people's songs as editable projects. Re-uploading a project you already published offers update in place (POST /custom_song/update) — the song keeps its music id and players keep their scores; unchanged audio/jackets are not re-sent.

Layout

• src-tauri/ — Rust backend: ew server HTTP client (server.rs), local project store (projects.rs, mirrors the server's export-package format), symphonia audio decoding (audio.rs).
• ui/ — frontend. No framework, no bundler: tsc emits native ES modules into ui/dist/js, index.html/styles.css are copied alongside. Tauri IPC via the withGlobalTauri bridge.
• Charts are stored and exchanged in the SIF1/NPPS4 JSON schema (the server's upload format); the server transcodes to SIF2 NoteData on upload.
• ui/src/convert/ — chart importers (⤓ Import in the editor, auto-detected): SIF1/NPPS4 JSON, official SIF2 NoteData (served JSON + Unity .asset YAML), Bandori .note (BMS, rules matched to bandori-sif2-tools), Bestdori JSON. Adding a format = one module implementing ChartConverter + one registry line.
• src-tauri/src/bundle.rs — minimal UnityFS AssetBundle reader: feed Import a raw .unity3d/musicscore bundle and it extracts TextAsset charts (Bandori) and Aoharu.NoteData MonoBehaviours (SIF2) directly, with a picker when a bundle holds several difficulties.
• src-tauri/src/bandori_batch.rs — batch import ("Batch import Bandori…" in Projects): feed it any mix of Bandori musicscoreNN (charts), sound/bgmNNN (audio as split CRI ACB → HCA → decoded via system ffmpeg, optional) and musicjacketNN bundles (ASTC textures → PNG); songs are grouped automatically, titles/bands come from the bestdori API (cached), and each selected song becomes a ready-to-edit project. Rules match bandori-sif2-tools.

Dependencies

Rust (stable, via rustup) and Node.js 18+ everywhere, plus the Tauri 2 system libraries:

Ubuntu / Debian

sudo apt install libwebkit2gtk-4.1-dev libgtk-3-dev libsoup-3.0-dev \
                 librsvg2-dev build-essential pkg-config curl

Fedora

sudo dnf install webkit2gtk4.1-devel gtk3-devel libsoup3-devel librsvg2-devel \
                 gcc gcc-c++ make pkgconf-pkg-config

Windows

Visual Studio Build Tools (the "Desktop development with C++" workload). The WebView2 runtime is preinstalled on Windows 10/11.

Develop

npm install
npx tauri dev        # runs `npm run build` first, then launches the app
npm run watch        # optional: tsc -w in a second terminal; Ctrl+R reloads the webview

Build a release binary

npx tauri build --no-bundle   # binary at src-tauri/target/release/charter

CI does this automatically: .forgejo/workflows/release.yml builds Linux + Windows binaries on every push and attaches them to a Forgejo release on every tag.

Editor quick reference

Input	Action
1 / 2 / 3 / 4	Select / Tap / Hold / Star tool
Click	Place note (drag to set a hold's length)
Drag note	Move it · drag a hold's tail to resize
Right-click	Delete note
Shift+click	Add to / remove from selection
Drag on empty space (select tool)	Box select
Del	Delete selection
Ctrl+Z / Ctrl+Y	Undo / redo
Ctrl+C / Ctrl+X / Ctrl+V	Copy / cut / paste at the playhead
Ctrl+A	Select all
Space	Play / pause
Home / End	Jump to start / end
↑ / ↓ (or ← / →)	Step the playhead by one snap division
Wheel	Scroll · Ctrl+wheel zoom · middle-drag pan
Click the waveform	Seek
⇆ toolbar button	Toggle vertical-scroll ⇄ horizontal-timeline layout

Everything autosaves; press ？ in the toolbar for this list in-app.