godot-composition-apps

name	godot-composition-apps
description	Expert architectural standards for building scalable Godot applications (Apps, Tools, UI, or Games) using the Composition pattern. Use when designing node structures, refactoring monolithic scripts, or implementing complex behaviors. Enforces "Has-A" relationships over "Is-A" inheritance.

Godot Composition & Architecture (Apps & UI)

This skill enforces the Single Responsibility Principle within Godot's Node system. Whether building an RPG or a SaaS Dashboard, the rule remains: One Script = One Job.

The Core Philosophy

The Litmus Test

Before writing a script, ask: "If I attached this script to a literal rock, would it still function?"

• Pass: An AuthComponent on a rock allows the rock to log in. (Context Agnostic)
• Fail: A LoginForm script on a rock tries to grab text fields the rock doesn't have. (Coupled)

The Backpack Model (Has-A > Is-A)

Stop extending base classes to add functionality. Treat the Root Node as an empty Backpack.

• Wrong (Inheritance): SubmitButton extends AnimatedButton extends BaseButton.
• Right (Composition): SubmitButton (Root) HAS-A AnimationComponent and HAS-A NetworkRequestComponent.

The Hierarchy of Power (Communication Rules)

Strictly enforce this communication flow to prevent "Spaghetti Code":

Direction	Source → Target	Method	Reason
Downward	Orchestrator → Component	Function Call	Manager owns the workers; knows they exist.
Upward	Component → Orchestrator	Signals	Workers are blind; they just yell "I'm done!"
Sideways	Component A ↔ Component B	FORBIDDEN	Siblings must never talk directly.

The Sideways Fix: Component A signals the Orchestrator; Orchestrator calls function on Component B.

The Orchestrator Pattern

The Root Node script (e.g., LoginScreen.gd, UserProfile.gd) is now an Orchestrator.

• Math/Logic: 0%
• State Management: 100%
• Job: Wire components together. Listen to Component signals and trigger other Component functions.

Example: App/UI Context

Concept	App/UI Example
Orchestrator	UserProfile.gd
Component 1	AuthValidator (Logic)
Component 2	FormListener (Input)
Component 3	ThemeManager (Visual)

Implementation Standards

1. Type Safety

Define components globally. Never use dynamic typing for core architecture.

# auth_component.gd
class_name AuthComponent extends Node

2. Dependency Injection

NEVER use get_node("Path/To/Child"). Paths are brittle. ALWAYS use Typed Exports and drag-and-drop in the Inspector.

# Orchestrator script
@export var auth: AuthComponent
@export var form_ui: Control

3. Scene Unique Names

If internal referencing within a scene is strictly necessary for the Orchestrator, use the % Unique Name feature.

@onready var submit_btn = %SubmitButton

4. Stateless Components

Components should process the data given to them.

• Bad: NetworkComponent finds the username text field itself.
• Good: NetworkComponent has a function login(username, password). The Orchestrator passes the text field data into that function.

Anti-Patterns (NEVER DO THIS)

1. The Monolith: A root script that handles UI events, HTTP requests, AND business logic.
2. The Chain: Passing data through 4 layers of nodes to get to the destination. (Use Signals).
3. Hard Dependency: InputComponent checking get_parent().health. (The component must work on a rock; rocks don't have health).

Code Structure Example (General App)

Component: clipboard_copier.gd

class_name ClipboardCopier extends Node

signal copy_success
signal copy_failed(reason)

func copy_text(text: String) -> void:
    if text.is_empty():
        copy_failed.emit("Text empty")
        return
    DisplayServer.clipboard_set(text)
    copy_success.emit()

Orchestrator: share_menu.gd

extends Control

# Wired via Inspector
@export var copier: ClipboardCopier
@export var link_label: Label

func _ready():
    # Downward communication
    %CopyButton.pressed.connect(_on_copy_button_pressed)
    # Upward communication listening
    copier.copy_success.connect(_on_copy_success)

func _on_copy_button_pressed():
    # Orchestrator delegation
    copier.copy_text(link_label.text)

func _on_copy_success():
    # Orchestrator managing UI state based on signal
    %ToastNotification.show("Link Copied!")

Reference

• Master Skill: godot-master