electron/docs/api/system-preferences.md
Zeke Sikelianos 6728efe87e Merge pull request #7339 from electron/document-return-values
Document the return values of all methods in the docs
2016-09-27 07:39:25 -07:00

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Markdown

# systemPreferences
> Get system preferences.
```javascript
const {systemPreferences} = require('electron')
console.log(systemPreferences.isDarkMode())
```
## Events
The `systemPreferences` object emits the following events:
### Event: 'accent-color-changed' _Windows_
Returns:
* `event` Event
* `newColor` String - The new RGBA color the user assigned to be there system
accent color.
## Methods
### `systemPreferences.isDarkMode()` _macOS_
Returns `Boolean` - Whether the the system is in Dark Mode.
### `systemPreferences.isSwipeTrackingFromScrollEventsEnabled()` _macOS_
Returns `Boolean` - Whether the Swipe between pages setting is on.
### `systemPreferences.postNotification(event, userInfo)` _macOS_
* `event` String
* `userInfo` Object
Posts `event` as native notifications of macOS. The `userInfo` is an Object
that contains the user information dictionary sent along with the notification.
### `systemPreferences.postLocalNotification(event, userInfo)` _macOS_
* `event` String
* `userInfo` Object
Posts `event` as native notifications of macOS. The `userInfo` is an Object
that contains the user information dictionary sent along with the notification.
### `systemPreferences.subscribeNotification(event, callback)` _macOS_
* `event` String
* `callback` Function
Subscribes to native notifications of macOS, `callback` will be called with
`callback(event, userInfo)` when the corresponding `event` happens. The
`userInfo` is an Object that contains the user information dictionary sent
along with the notification.
The `id` of the subscriber is returned, which can be used to unsubscribe the
`event`.
Under the hood this API subscribes to `NSDistributedNotificationCenter`,
example values of `event` are:
* `AppleInterfaceThemeChangedNotification`
* `AppleAquaColorVariantChanged`
* `AppleColorPreferencesChangedNotification`
* `AppleShowScrollBarsSettingChanged`
### `systemPreferences.unsubscribeNotification(id)` _macOS_
* `id` Integer
Removes the subscriber with `id`.
### `systemPreferences.subscribeLocalNotification(event, callback)` _macOS_
* `event` String
* `callback` Function
Same as `subscribeNotification`, but uses `NSNotificationCenter` for local defaults.
This is necessary for events such as `NSUserDefaultsDidChangeNotification`
### `systemPreferences.unsubscribeLocalNotification(id)` _macOS_
* `id` Integer
Same as `unsubscribeNotification`, but removes the subscriber from `NSNotificationCenter`.
### `systemPreferences.getUserDefault(key, type)` _macOS_
* `key` String
* `type` String - Can be `string`, `boolean`, `integer`, `float`, `double`,
`url`, `array`, `dictionary`
Get the value of `key` in system preferences.
This API reads from `NSUserDefaults` on macOS, some popular `key` and `type`s
are:
* `AppleInterfaceStyle: string`
* `AppleAquaColorVariant: integer`
* `AppleHighlightColor: string`
* `AppleShowScrollBars: string`
* `NSNavRecentPlaces: array`
* `NSPreferredWebServices: dictionary`
* `NSUserDictionaryReplacementItems: array`
### `systemPreferences.isAeroGlassEnabled()` _Windows_
This method returns `true` if [DWM composition][dwm-composition] (Aero Glass) is
enabled, and `false` otherwise.
An example of using it to determine if you should create a transparent window or
not (transparent windows won't work correctly when DWM composition is disabled):
```javascript
const {BrowserWindow, systemPreferences} = require('electron')
let browserOptions = {width: 1000, height: 800}
// Make the window transparent only if the platform supports it.
if (process.platform !== 'win32' || systemPreferences.isAeroGlassEnabled()) {
browserOptions.transparent = true
browserOptions.frame = false
}
// Create the window.
let win = new BrowserWindow(browserOptions)
// Navigate.
if (browserOptions.transparent) {
win.loadURL(`file://${__dirname}/index.html`)
} else {
// No transparency, so we load a fallback that uses basic styles.
win.loadURL(`file://${__dirname}/fallback.html`)
}
```
[dwm-composition]:https://msdn.microsoft.com/en-us/library/windows/desktop/aa969540.aspx
### `systemPreferences.getAccentColor()` _Windows_
Returns the users current system wide color preference in the form of an RGBA
hexadecimal string.
```js
const color = systemPreferences.getAccentColor() // `"aabbccdd"`
const red = color.substr(0, 2) // "aa"
const green = color.substr(2, 2) // "bb"
const blue = color.substr(4, 2) // "cc"
const alpha = color.substr(6, 2) // "dd"
```