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https://github.com/fmpallini/partydisplay

Party Display is Windows desktop application (Tauri v2) that shows a fullscreen photo slideshow on a projector or TV, synchronized to the music playing. Think of it as a smart jukebox backdrop — your photos, your playlist, your party.
https://github.com/fmpallini/partydisplay

casting music photo slideshow spotify

Last synced: 22 days ago
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Party Display is Windows desktop application (Tauri v2) that shows a fullscreen photo slideshow on a projector or TV, synchronized to the music playing. Think of it as a smart jukebox backdrop — your photos, your playlist, your party.

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README 

          
# Party Display



> A vibe coding exercise — building a real Spotify-connected party display, driven entirely by AI agents.



---



## What is this?



Party Display is a desktop application that registers as a **Spotify Connect device** and shows a fullscreen photo slideshow on a projector or TV, synchronized to the music playing. Think of it as a smart jukebox backdrop — your photos, your playlist, your party.



The app is being built on **Tauri v2** (Windows), using the **Spotify Web Playback SDK** for device registration and audio, **WASAPI loopback** (via Rust) for real-time spectrum visualization, and the **Spotify Audio Analysis API** for beat-synchronized photo transitions.



---



## This is a vibe coding exercise



This project is an experiment in **agentic software development** applied to a non-trivial problem. The goal is not just to build the app — it's to explore how far AI agents can go when the problem involves:



- External service integrations (Spotify OAuth, Web Playback SDK, Widevine DRM)

- System-level concerns (audio capture, native desktop runtime)

- Real unknowns that require investigation, not just code generation



Every spike, plan, and implementation task in this repo was driven by **Claude Code** and its agent ecosystem. The human role was product direction, validation, and unblocking — not writing code.



---



## Agents involved



| Agent | Role |

|---|---|

| **Claude Code** (main session) | Architect, debugger, coordinator — ran the entire project loop |

| **Implementer subagents** | Executed individual implementation tasks in isolated context windows |

| **Spec reviewer subagents** | Verified each task matched the plan before proceeding |

| **Code quality reviewer subagents** | Reviewed implementation quality after spec compliance |

| **Explore subagents** | Searched the codebase and gathered evidence during debugging |



The agent workflow followed the **superpowers skill suite** — `writing-plans` to design tasks, `subagent-driven-development` to execute them with two-stage review, and `systematic-debugging` to avoid guessing when things broke.



---



## The spikes



Before writing a single line of production code, three validation spikes were run to answer hard questions about the tech stack.



### Spike 1 — Electron + castlabs Widevine (`spike/` — first attempt)



**Question:** Can the Spotify Web Playback SDK run inside Electron?



**Findings:**

- Device registration worked

- Audio played — but every track failed with a `playback_error` at ~1 second, then auto-skipped

- Root cause: the castlabs Electron Widevine CDM was rejected by Spotify's license server at the DRM renewal boundary

- The Web Audio FFT tap also failed — the SDK sandboxes audio inside a **cross-origin iframe**, making `AudioContext` access impossible from the parent page



**Decision:** Drop Electron.



---



### Spike 2 — Browser (Node.js HTTPS + Chrome) (`spike/`)



**Question:** Does the SDK work properly in a real browser?



**Findings:**

- Playback was flawless — zero skipping, no DRM errors (Chrome's native Widevine is fully compatible)

- Confirmed the cross-origin iframe limitation: Chrome's Web Audio Inspector showed **"No Web Audio API usage detected"** while music played

- OAuth PKCE redirect to `https://localhost` was blocked by Spotify ("redirect_uri: Insecure") — a known Spotify quirk around loopback URIs



**Decision:** Browser runtime is valid, but needs a desktop wrapper for OAuth and the audio tap problem needs a different solution.



---



### Spike 3 — Tauri v2 (`spike-tauri/`) ✅



**Question:** Does Tauri's WebView2 satisfy Spotify's Widevine DRM? Can Rust capture system audio via WASAPI loopback?



**Findings:**

- **WebView2 + Widevine:** Device registered instantly, music played with zero skipping. WebView2 (Edge's Chromium engine) ships a native, fully compatible Widevine CDM.

- **WASAPI loopback:** `cpal 0.15` + `rustfft 6` successfully captured system audio output, ran FFT, and streamed 64 frequency bins to the frontend via Tauri events. FFT sum: **753 non-zero** on first run.

- Live spectrum canvas animated in real time while Spotify played.



**Decision:** Tauri v2 on Windows is the confirmed foundation.



![Spike 3 — Tauri v2 running on Windows](spike-tauri/spike_tauri_windows.png)



*Live capture: Spotify SDK connected, WASAPI loopback active, spectrum canvas animating — FFT sum 753 non-zero on first run.*



---



## Architecture (Phase 2)



```

┌─────────────────────────────────────────┐

│              Tauri v2 App               │

│                                         │

│  ┌──────────────┐  ┌──────────────────┐ │

│  │ Control Panel│  │  Display Window  │ │

│  │  (WebView2)  │  │   (WebView2)     │ │

│  │              │  │                  │ │

│  │ Spotify SDK  │  │ Photo Slideshow  │ │

│  │ OAuth / Auth │  │ Now Playing HUD  │ │

│  │ Volume / Skip│  │ Spectrum Canvas  │ │

│  └──────┬───────┘  └────────┬─────────┘ │

│         │                   │           │

│  ┌──────▼───────────────────▼─────────┐ │

│  │           Rust Backend             │ │

│  │                                    │ │

│  │  WASAPI loopback → FFT → events    │ │

│  │  Spotify Audio Analysis API        │ │

│  │  OAuth PKCE + token refresh        │ │

│  │  Slideshow engine (folder watch)   │ │

│  │  IPC channels (typed)              │ │

│  └────────────────────────────────────┘ │

└─────────────────────────────────────────┘

```



**Tech stack:** Tauri 2 · Rust · React · TypeScript · Vite · cpal · rustfft · Spotify Web Playback SDK · Spotify Web API



---



## Project structure



```

vcup2/

├── spike/              # Spike 2: browser validation (Node.js + Chrome)

├── spike-tauri/        # Spike 3: Tauri v2 validation ✅ (confirmed stack)

├── docs/

│   └── superpowers/

│       └── plans/      # Agent-generated implementation plans

└── README.md

```



---



## Status



- [x] Spike 1 — Electron (abandoned)

- [x] Spike 2 — Browser (validated SDK + found FFT limitation)

- [x] Spike 3 — Tauri v2 (validated full stack) ✅

- [x] Phase 2 — Full app implementation (**v0.5 Beta**)



---



## v0.5 Beta — Current state



The app is functional and in daily use. All core features are implemented. Below is a full feature inventory as of this release.



### Spotify integration



- Registers as a **Spotify Connect device** via the Web Playback SDK running inside WebView2

- Full **OAuth PKCE** flow — browser opens for auth, redirect is caught by a single-instance deep-link handler, tokens stored in the Windows credential store (keyring)

- Automatic **token refresh** — sessions survive app restarts without re-auth

- **Now playing** card: album art, track name, artist, progress bar with seek

- Transport controls: play/pause, previous, next

- **Volume** slider with live feedback; volume changes emitted to the display window as toast notifications



### Photo slideshow



- Folder picker — watches a local folder for images (JPEG/PNG/WebP/GIF)

- Optional **recursive subfolder** scan

- **Play order**: alphabetical (with resume-from-last across restarts) or shuffle

- Configurable **fixed display time** per photo (seconds)

- **8 transition effects**: fade, slide left/right/up/down, zoom in/out, blur — plus a **random** mode that picks a different effect each advance

- Configurable **transition duration**

- **Image fit**: fill (cover/crop) or letterbox (contain)

- **Keyboard hotkeys** on the display window: `→`/`←` next/prev, `Space` pause/resume, `F` fullscreen, `S` spectrum, `T` track overlay, `B` battery



### Display window



- Runs in a separate window — intended for a second monitor, projector or TV

- **Fullscreen** toggle via double-click or Escape to exit

- Window position and fullscreen state **persisted** across restarts

- Position **validated against available monitors** on restore — repositioned to primary if the saved monitor is gone

- **Screensaver / sleep blocked** via `SetThreadExecutionState` while the display window is open

- Close button in control panel stays in sync even if the user closes the display window manually



### Spectrum analyser overlay



- Real-time **WASAPI loopback** audio capture (Rust — no driver install needed)

- **64-bin FFT** with logarithmic frequency mapping (40 Hz – 16 kHz) — eliminates the empty high-frequency bins that linear mapping produces

- Exponential smoothing with **fast attack / slow decay** for a polished, flicker-free look

- Two render styles: **bars** or **lines** (filled gradient area + stroke)

- Six colour themes: Energy (green→red), Cyan, Fire, White, Rainbow, Purple

- Configurable **height** as % of screen (default 10%) — true overlay, photo uses full screen underneath

- Toggled with the `S` hotkey

- A small **audio indicator** strip is also shown in the control panel Music card



### Track overlay



- Optional **"artist — title" overlay** on the display window, toggled with `T`

- Configurable: font family, font size, corner position (top/bottom × left/right), text colour, background colour, background opacity

- Artist name shown smaller above the track title



### Battery widget



- SVG battery icon in the top-right corner of the display window

- **5-step colour scale**: green → yellow-green → yellow → orange → red

- Lightning bolt overlay when charging; plug icon on desktops with no battery

- Configurable size; can be disabled



### Song & volume toasts



- **Song changed toast**: album art + track name slides in when the track changes, auto-dismisses

- **Volume changed toast**: compact level indicator on volume change

- Configurable display duration and scale



### Control panel



- Card-based layout with sticky header and vertical scroll

- **Cards**: Music, Slideshow, Display Window, Display Settings (collapsible)

- All display settings live-synced to the display window without restart



### Help panel



- `?` button in the header opens a modal with: app description, GitHub link, hotkeys reference table

- **Reset button**: clears all `localStorage` settings + Spotify credentials from the credential store, then relaunches the app — useful for diagnosing unknown issues



### App icon



- Custom icon: gold treble clef on a dark purple/navy gradient canvas with a gold painting frame and colourful paint-splash accents

- All platform sizes generated (Windows ICO, macOS ICNS, iOS, Android)



---



## Hotkeys (display window)



| Key | Action |

|---|---|

| `→` / `←` | Next / previous photo |

| `Space` | Pause / resume slideshow |

| `F` | Toggle fullscreen |

| `S` | Toggle spectrum analyser |

| `T` | Toggle track overlay |

| `B` | Toggle battery icon |

| `Esc` | Exit fullscreen |

| Double-click | Toggle fullscreen |



---



## License



GNU AGPL v3 — see [LICENSE](LICENSE).