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Idle Decorators

The Idle decorators allow you to easily respond to changes in the system's idle state in your extension service. These decorators provide a clean way to track when the system becomes active, idle, or locked.

Method Decorators​

onIdleStateChanged​

This decorator handles events that fire when the system changes to an active, idle or locked state.

import { onIdleStateChanged, InjectableService } from 'deco-ext';

@InjectableService()
class IdleMonitor {
  @onIdleStateChanged()
  handleStateChange(newState: browser.Idle.IdleState) {
    console.log(`System state changed to: ${newState}`);
    
    // newState will be one of: "active", "idle", or "locked"
    if (newState === "idle") {
      console.log("User is away");
    } else if (newState === "active") {
      console.log("User has returned");
    } else if (newState === "locked") {
      console.log("Device is locked");
    }
  }
}

Idle States​

The Chrome idle API reports three possible states:

  • active: The user is actively using the device
  • idle: The device has not received user input for the specified idle detection interval
  • locked: The screen is locked or the screensaver is active

Implementation Details​

This decorator uses a singleton pattern to ensure only one event listener is registered for the idle state change event, and then routes events to all decorated methods. When the idle state changes:

  1. The event is received by the single registered browser API listener
  2. The event data (newState) is passed to all registered method handlers
  3. For each handler:
    • The class instance is resolved from the dependency injection container
    • If the class has an init method, it's called before handling the event
    • The method is called with the new idle state as a parameter

The decorator can only be used on methods within classes that have been decorated with the InjectableService decorator from deco-ext.

Use Cases​

The idle API is particularly useful for:

  • Pausing CPU-intensive operations when the user is away
  • Securing sensitive data when the user is inactive
  • Tracking user activity for analytics purposes
  • Implementing auto-save features
  • Showing different content based on user activity state