ModUIClient

Fabric client mod that renders Nukkit ModUI HUD and Stack UI on Minecraft Java Edition, bridged through ViaBedrock / ViaProxy.

Overview

Nukkit servers (Bedrock Edition) use a custom UI framework called ModUI to display HUD overlays and modal screens. This mod implements a client-side renderer that interprets ModUI protocol messages (PY_RPC MsgPack) and renders them as native Java Edition UI elements.

Nukkit Server (Bedrock) ──PY_RPC──► ViaBedrock ──CustomPayload──► ModUIClient (this mod)
                                                                        │
                                                                   UIManager
                                                                   ├── HUD Tree (always visible overlay)
                                                                   └── Stack Tree (modal screen)

Features

• HUD Overlay: Persistent UI elements rendered on top of the game (health bars, score displays, notifications)
• Stack Screen: Modal UI screens (menus, dialogs) that capture input
• Layout Engine: Bedrock-compatible layout system with anchor points, percentage sizes, and stack panels
• Element Types:
  • image / imageElongate / imageTop - Texture rendering with UV mapping, nine-slice, sprite sheet animation, rotation
  • text / textLeft / textRight - Multi-line text with font scaling, alignment, auto-wrapping, line padding
  • button / buttonSlice - Interactive buttons with hover/pressed states and nine-slice support
  • panel / stackPanel - Container elements with horizontal/vertical stacking
• Size Expressions: 100% (parent), 100%c (children sum), 100%cm (max child), 100%sm (max sibling), 50% + 10 (arithmetic)
• Incremental Commands: 25+ command types for runtime UI manipulation (SetText, SetVisible, AddElement, RemoveElement, etc.)
• C2S Events: Button click reporting, screen info synchronization

Requirements

• Minecraft 1.21.11
• Fabric Loader >= 0.16.10
• Fabric API
• Java 21+
• ViaProxy with ViaBedrock (for protocol bridging)

Building

./gradlew build

Output jar: build/libs/moduiclient-1.0.0.jar

Installation

Copy the built jar to your Fabric client's mods/ directory alongside Fabric API.

Protocol

S2C Events (Server → Client)

Event	Description
ResponseHudNodeDataEvent	Initialize HUD element tree from JSON
RequestCreateStackNodeEvent	Open a modal Stack UI screen
RequestControlNodeEvent	Execute incremental UI commands
RequestRemoveStackNodeEvent	Close the Stack UI

C2S Events (Client → Server)

Event	Description
RequestHudNodeDataEvent	Request HUD data from server
RequestClickHudBtEvent	Report HUD button click
RequestClickStackBtEvent	Report Stack button click
ScreenInfoEvent	Send screen resolution info

License

MIT