godot-composition-apps

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":

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

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