electron/docs/api/power-monitor.md

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# powerMonitor
> Monitor power state changes.
Process: [Main](../glossary.md#main-process)
## Events
The `powerMonitor` module emits the following events:
### Event: 'suspend'
Emitted when the system is suspending.
### Event: 'resume'
Emitted when system is resuming.
### Event: 'on-ac' _macOS_ _Windows_
Emitted when the system changes to AC power.
### Event: 'on-battery' _macOS_ _Windows_
Emitted when system changes to battery power.
### Event: 'shutdown' _Linux_ _macOS_
Emitted when the system is about to reboot or shut down. If the event handler
invokes `e.preventDefault()`, Electron will attempt to delay system shutdown in
order for the app to exit cleanly. If `e.preventDefault()` is called, the app
should exit as soon as possible by calling something like `app.quit()`.
### Event: 'lock-screen' _macOS_ _Windows_
Emitted when the system is about to lock the screen.
### Event: 'unlock-screen' _macOS_ _Windows_
Emitted as soon as the systems screen is unlocked.
### Event: 'user-did-become-active' _macOS_
Emitted when a login session is activated. See [documentation](https://developer.apple.com/documentation/appkit/nsworkspacesessiondidbecomeactivenotification?language=objc) for more information.
### Event: 'user-did-resign-active' _macOS_
Emitted when a login session is deactivated. See [documentation](https://developer.apple.com/documentation/appkit/nsworkspacesessiondidresignactivenotification?language=objc) for more information.
## Methods
The `powerMonitor` module has the following methods:
### `powerMonitor.getSystemIdleState(idleThreshold)`
* `idleThreshold` Integer
Returns `string` - The system's current state. Can be `active`, `idle`, `locked` or `unknown`.
Calculate the system idle state. `idleThreshold` is the amount of time (in seconds)
before considered idle. `locked` is available on supported systems only.
### `powerMonitor.getSystemIdleTime()`
Returns `Integer` - Idle time in seconds
Calculate system idle time in seconds.
### `powerMonitor.isOnBatteryPower()`
Returns `boolean` - Whether the system is on battery power.
To monitor for changes in this property, use the `on-battery` and `on-ac`
events.
## Properties
### `powerMonitor.onBatteryPower`
A `boolean` property. True if the system is on battery power.
See [`powerMonitor.isOnBatteryPower()`](#powermonitorisonbatterypower).