Atom Engine

Input

Purpose

The Input class is a high-level wrapper around a low-level input system. It manages keyboard state tracking, including key presses and held states, while optionally filtering out “blocked” keys (e.g., arrow keys, space, and specific action keys). It provides a simplified API for querying input state in game loops or interactive applications.

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Lifecycle

Creation → Update → Destruction

• Creation
  • An InputState is created via createInputState(blockedKeys).
  • Global or event-based listeners are attached using attachInput.
  • The instance begins tracking keyboard input immediately.
• Update
  • The internal InputState is updated implicitly via event listeners.
  • Consumers query state through isDown and isPressed.
  • Pressed-state transitions are typically frame-based and must be cleared manually.
• Destruction
  • No explicit teardown is implemented in this class.
  • If needed, cleanup must be handled externally in the underlying input system.

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Public API

constructor(blockedKeys?: string[])

Creates a new input handler instance.

• Parameters
  • blockedKeys (optional): Array of key identifiers to ignore in input processing.
    • Default: ["ArrowUp", "ArrowDown", "ArrowLeft", "ArrowRight", " ", "e"]

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isDown(key: string): boolean

Checks whether a key is currently being held down.

• Returns
  • true if the key is currently pressed
  • false otherwise

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isPressed(key: string): boolean

Checks whether a key was pressed during the current update cycle.

• Returns
  • true if the key transitioned from up → down in the current frame
  • false otherwise

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clearPressed(): void

Resets all “pressed” states.

• Typically called once per frame after input has been processed.

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getState(): InputState

Returns the underlying input state object.

• Returns
  • The internal InputState instance used for tracking input

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Internal Behavior

• The class depends on an external input module (../input) that provides:
  • InputState type
  • createInputState(blockedKeys) for initialization
  • attachInput(state) for registering event listeners
  • isKeyDown(state, key) for continuous input checks
  • isKeyPressed(state, key) for edge-triggered input detection
  • clearPressed(state) for resetting per-frame press flags

• blockedKeys are passed at initialization and used by the underlying system to filter unwanted or reserved inputs.

• The class itself does not directly listen to events; it delegates all input tracking to the shared InputState.

• It acts as a thin abstraction layer to simplify usage in game loops or UI systems.

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Example

import { Input } from "./Input";

const input = new Input();

// Game loop
function update() {
    if (input.isDown("ArrowLeft")) {
        console.log("Moving left continuously");
    }

    if (input.isPressed(" ")) {
        console.log("Jump triggered");
    }

    // Reset per-frame press states
    input.clearPressed();
}

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Related Elements

• InputState – Internal structure storing key states
• createInputState – Initializes input tracking state
• attachInput – Hooks keyboard event listeners
• isKeyDown – Checks continuous key state
• isKeyPressed – Checks edge-triggered key state
• clearPressed – Resets per-frame key press flags