Doze

Always-on Display (AOD) provides an alternative ‘screen-off’ experience. Instead, of completely turning the display off, it provides a distraction-free, glanceable experience for the phone in a low-powered mode. In this low-powered mode, the display will have a lower refresh rate and the UI should frequently shift its displayed contents in order to prevent burn-in. The recommended max on-pixel-ratio (OPR) is 5% to reduce battery consumption.

The default doze component controls AOD and is specified by config_dozeComponent in the framework config. SystemUI provides a default Doze Component: DozeService. DozeService builds a DozeMachine with dependencies specified in DozeModule and configurations in AmbientDisplayConfiguration and DozeParameters.

Note: The default UI used in AOD shares views with the Lock Screen and does not create its own new views. Once dozing begins, DozeUI informs SystemUI's DozeServiceHost that dozing has begun - which sends this signal to relevant SystemUI Lock Screen views to animate accordingly. Within SystemUI, StatusBarStateController #isDozing and #getDozeAmount can be used to query dozing state. DozeMachine handles the following main states:

• AOD - persistently showing UI when the device is in a low-powered state
• Pulsing - waking up the screen to show notifications (from AOD and screen off)
• Docked UI - UI to show when the device is docked
• Wake-up gestures - including lift to wake and tap to wake (from AOD and screen off)

Doze States (see DozeMachine.State)

DOZE

Device is asleep and listening for enabled pulsing and wake-up gesture triggers. In this state, no UI shows.

DOZE_SUSPEND_TRIGGERS

Device is asleep and not listening for any triggers to wake up. This state is used only when CAR_MODE is active. In this state, no UI shows.

DOZE_AOD

Device is asleep, showing UI, and listening for enabled pulsing and wake-up triggers. In this state, screen brightness is handled by DozeScreenBrightness which uses the brightness sensor specified by doze_brightness_sensor_type in the SystemUI config. To save power, this should be a low-powered sensor that shouldn't trigger as often as the light sensor used for on-screen adaptive brightness.

DOZE_AOD_PAUSED

Device is asleep and would normally be in state DOZE_AOD; however, instead the display is temporarily off since the proximity sensor reported near for a minimum abount of time. DozePauser handles transitioning from DOZE_AOD_PAUSING after the minimum timeout after the NEAR is reported by the proximity sensor from DozeTriggers).

DOZE_PULSING

Device is awake and showing UI. This is state typically occurs in response to incoming notification, but may also be from other pulse triggers specified in DozeTriggers.

DOZE_AOD_DOCKED

Device is awake, showing docking UI and listening for enabled pulsing and wake-up triggers. The default DockManager is provided by an empty interface at DockManagerImpl. SystemUI should override the DockManager for the DozeService to handle docking events.

DozeDockHandler listens for Dock state changes from DockManager and updates the doze docking state.

Wake-up gestures

Doze sensors are registered in DozeTriggers via DozeSensors. Sensors can be configured per posture for foldable devices.

Relevant sensors include:

• Proximity sensor
• Brightness sensor
• Wake-up gestures
  • tap to wake
  • double tap to wake
  • lift to wake
  • significant motion

And are configured in the AmbientDisplayConfiguration with some related configurations specified in DozeParameters.

Doze Suppressors

When Dozing is enabled, it can still be suppressed based on the device state. On a high-level, doze and/or AOD may be suppressed if the device is:

• in CAR_MODE
• not provisioned
• in power saver mode
• being suppressed by an app (see PowerManager#suppressAmbientDisplay)

Refer to the documentation in DozeSuppressors for more information.

AOD burn-in and image retention

Because AOD will show an image on the screen for an elogated period of time, AOD designs must take into consideration burn-in (leaving a permanent mark on the screen). Temporary burn-in is called image-retention.

To prevent burn-in, it is recommended to often shift UI on the screen. DozeUi schedules a call to dozeTimeTick every minute to request a shift in UI for all elements on AOD. The amount of shift can be determined by undergoing simulated AOD testing since this may vary depending on the display.

For manual local testing, set DozeUI#BURN_IN_TESTING_ENABLED to true, and then manual time broadcasts (ie: adb shell 'date 022202222022.00 ; am broadcast -a android.intent.action.TIME_SET') will update the burn-in translations of the views. For a general idea where burn-in may be an issue, run the software burn-in script.

Debugging Tips

Enable DozeLog to print directly to logcat:

adb shell settings put global systemui/buffer/DozeLog v

Enable all DozeService logs to print directly to logcat:

adb shell setprop log.tag.DozeService DEBUG

Other helpful dumpsys commands (adb shell dumpsys <service>):

• activity service com.android.systemui/.doze.DozeService
• activity service com.android.systemui/.SystemUIService
• display
• power
• dreams
• sensorservice