Layer System

A lightweight, flexible system for managing stateful layers in games or UI applications. Perfect for handling menus, game states, and event propagation with minimal boilerplate.

Features

• Layer Stack: Add and remove layers dynamically (contains the game, useful for adding pause menu, HUD, and similar).
• Event Flow:
  • update(): Top-to-bottom, might stop early (useful for pause menus, clicks, and also general game update).
  • passive_update(): Bottom-to-top, always executed for every layer (especially useful for rendering)
• Generic: Works with any State and Event types.

Quick Example

use layer_system::{Change, Layer, LayerManager};

// 1. Define Events
enum Event {
    Fixed,
    Click(u16, u16),
    Quit,
}

// 2. Implement Layers
struct World;
impl Layer<(), Event> for World {
    fn update(&mut self, _: &mut (), event: &Event) -> Change<(), Event> {
        match event {
            Event::Fixed => {
                /* physics */
                Change::none()
            }
            _ => Change::pass(),
        }
    }
}

// 3. Run
let mut manager = LayerManager::new(vec![Box::new(World)]);
manager.update(&mut (), Event::Fixed);

Key Concepts

Change Actions

When to Use

• Games: Main menu → Game world → Pause screen transitions.
• UI: Modal dialogs, tooltips, or stacked panels.
• Simulations: Layered behavior.