# 29 - Client HUD & Protocol

The Iris client mod (Fabric/Forge/NeoForge jar on the client) adds a native pregeneration HUD, Vision map, What overlay, studio toasts, and singleplayer world-type entries. It talks to Iris servers over the shared channel `irisworldgen:main`. Vanilla clients ignore the channel and use server-side fallbacks. See also `07 - Pregeneration.md`, `08 - Localization.md`, `10 - Studio & VSCode Schemas.md`, and `30 - Platform Differences.md`.

## When the client mod does something

| Server | Client without Iris | Client with Iris mod |
|---|---|---|
| Modded Iris | Boss bar / status for pregen | Native HUD over custom payloads |
| Bukkit/Paper Iris | Console/status and any Bukkit HUD lanes; no Iris client protocol features | Same native HUD/Vision/What over plugin messaging on `irisworldgen:main` |
| Non-Iris server | N/A | Client mod is inert after hello fails / no Iris |

Singleplayer: installed packs appear as selectable World Types; the integrated server runs the same engine.

## Keybinds

Category: **Iris** (`key.categories.irisworldgen.iris`). Defaults:

| Action | Default key | Translation key |
|---|---|---|
| Toggle pregen HUD | `H` | `key.irisworldgen.toggle_pregen_hud` |
| Open Iris Vision map | `M` | `key.irisworldgen.open_vision_map` |
| Toggle Iris What overlay | `J` | `key.irisworldgen.toggle_what_overlay` |

Keys are rebindable in Controls under the Iris category. HUD visibility defaults on (`hudVisible = true`). What overlay defaults off. F1 hide-gui still advances toasts via a separate tick so they are not stranded.

## Pregen HUD

Top-left panel (`ORIGIN` 6,6) while a live pregen job is tracked and not expired:

| Element | Content |
|---|---|
| Title | Localized pregen header |
| Stats | `done / total (percent%)` |
| Bar | Green while running, yellow while paused, muted gray when stale |
| Tail | Rate, optional ETA, `PAUSED`, or “no updates for Ns” when stale |
| Minimap | Optional region grid when region deltas exist (pending / generating / done cells) |

Stale and expire timers (client-side, from last received progress frame):

| Threshold | Value | Effect |
|---|---|---|
| Stale | 5 s | Panel mutes colors and shows stale label |
| Expire | 30 s | Panel stops drawing |

`PregenEnd` clears the job immediately. Hide-gui (F1) skips layered HUD draw; toasts still pump.

## Boss bar fallback

Modded servers: `ModdedPregenBossBar` shows a green (running) / yellow (paused) boss bar to the player who started pregen **only if** that player does not already have a ready protocol session with `CAPABILITY_PREGEN`. Clients with a working pregen HUD skip the boss bar. Bar title uses localized `iris.runtime.pregen.bossbar.*` strings; progress updates every 10 ticks.

Bukkit-family servers: players without the client mod do not get this modded boss-bar path; use `/iris pregen status`, logging, and any server HUD lanes. Clients with the mod still receive protocol pregen frames over plugin messaging.

## Vision map and What overlay

| Feature | Capability | Notes |
|---|---|---|
| Vision map (`M`) | `CAPABILITY_VISION` | Full-screen map; drag pan, scroll zoom, Esc close; needs ready session + Iris dimension |
| What overlay (`J`) | `CAPABILITY_CURSOR` | Cursor column query: biome, region, cave biome, height |
| Studio toasts | Client advertises `CAPABILITY_STUDIO` | Hotload/toast frames when the server sends them |
| Dimension status | Always after hello | Pack/dimension/height bounds; non-Iris worlds clear tiles/markers |

Vision tiles arrive chunked (max payload per chunk 24000 bytes; header 25 bytes). Markers capped at 256 per frame.

## Protocol channel

| Constant | Value |
|---|---|
| Channel | `irisworldgen:main` |
| Protocol version | `1` |
| Transport (modded) | Custom payloads on the play channel |
| Transport (Bukkit) | Plugin messaging in/out on the same channel name |
| Max frame | 24576 bytes |
| Max inbound frames / client / s | 32 |
| Max vision tile requests / s | 8 |
| Max cursor info requests / s | 4 |
| Max query `|block|` coordinate | 29_999_999 |

Internal wire types (`IrisProtocol.TYPE_*`):

| Id | Direction | Message |
|---|---|---|
| 1 | C→S | `ClientHello` (version, capabilities) |
| 2 | S→C | `ServerHello` (version, capabilities, brand, irisActive) |
| 3 | S→C | `PregenProgress` |
| 4 | S→C | `PregenEnd` |
| 5 | S→C | `DimensionStatus` |
| 6 | C→S | `CursorInfoRequest` |
| 7 | S→C | `CursorInfo` |
| 8 | C→S | `VisionTileRequest` |
| 9 | S→C | `VisionTile` (chunked) |
| 10 | S→C | `VisionMarkers` |
| 11 | S→C | `PregenRegionDelta` |
| 12 | S→C | `StudioHotload` |
| 13 | S→C | `Toast` |

Capability bits:

| Bit | Name | Meaning |
|---|---|---|
| `1 << 0` | `CAPABILITY_PREGEN` | Pregen progress / end / region deltas |
| `1 << 1` | `CAPABILITY_VISION` | Vision tiles and markers |
| `1 << 2` | `CAPABILITY_CURSOR` | Cursor column lookups |
| `1 << 3` | `CAPABILITY_STUDIO` | Studio hotload notifications |

Client hello advertises all four. Bukkit and modded servers grant `PREGEN | VISION | CURSOR | STUDIO`. Negotiated capabilities are the intersection of what the client advertises and what the server grants.

## Handshake

1. Client joins world → sends `ClientHello` with protocol version `1` and client capabilities.
2. Retries every 2 s, max 5 attempts; failure → session `UNSUPPORTED`.
3. Version mismatch → session `INCOMPATIBLE` (UI can report mismatch).
4. Match → session `READY`; dimension status and feature frames follow.
5. Disconnect clears session and world-local client state (pregen, tiles, markers, cursor, toasts).

Server drops frames before hello, rate-limits, rejects oversized/malformed frames, and rejects out-of-bounds cursor queries without clamping.

## Localization touchpoints

Server-side locale (`general.language`) drives boss bar and many shared UI strings. Client keybind labels use `assets/irisworldgen/lang/*.json`. Vision/What/pregen HUD strings use `ClientUiMessages` through `IrisLanguage`. See `08 - Localization.md`.

## Operator verification

- Modded server + Iris client: pregen progress on HUD; boss bar absent for that player when protocol pregen capability is ready
- Bukkit Iris + Iris client: same HUD over plugin messaging
- Vanilla client on either server: no protocol traffic effects; modded boss bar path as above
- Non-Iris server + Iris client: mod inert
- H toggles HUD; M opens Vision when available; J toggles What when available