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| <title>Implementing Night Light</title> |
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| <p> |
| Research suggests that blue light from screens can have a negative impact on |
| sleep. Android 7.1.1 includes a feature called Night Light that reduces the |
| amount of blue light emitted by the device display to better match the natural |
| light of the user's time of day and location. Android 8.0 includes a feature |
| that gives users more control over the intensity of the Night Light effect. |
| </p> |
| <p> |
| Night Light requires a |
| <a href="/devices/graphics/implement-hwc.html">Hardware |
| Composer HAL 2.0</a> (HWC 2) implementation that can apply the matrix passed to |
| <code>setColorTransform</code> to perform tinting without impacting power, |
| performance, and app compatibility. |
| </p> |
| <h2 id="implementation">Implementation</h2> |
| <p> |
| Device manufacturers can enable the default implementation of the feature by |
| using the following flags defined in: |
| <code><a href="https://android.googlesource.com/platform/frameworks/base/+/master/core/res/res/values/config.xml"> |
| /android/frameworks/base/core/res/res/values/config.xml</a></code> |
| |
| <pre class="devsite-click-to-copy"> |
| <!-- Control whether Night display is available. This should only be enabled |
| on devices with HWC 2 color transform support. --> |
| <bool name="config_nightDisplayAvailable">false</bool> |
| <!-- Default mode to control how Night display is automatically activated. |
| One of the following values (see NightDisplayController.java): |
| 0 - AUTO_MODE_DISABLED |
| 1 - AUTO_MODE_CUSTOM |
| 2 - AUTO_MODE_TWILIGHT |
| --> |
| <integer name="config_defaultNightDisplayAutoMode">0</integer> |
| <!-- Default time when Night display is automatically activated. |
| Represented as milliseconds from midnight (e.g. 79200000 == 10pm). --> |
| <integer name="config_defaultNightDisplayCustomStartTime">79200000</integer> |
| <!-- Default time when Night display is automatically deactivated. |
| Represented as milliseconds from midnight (e.g. 21600000 == 6am). --> |
| <integer name="config_defaultNightDisplayCustomEndTime">21600000</integer> |
| |
| <!-- Minimum color temperature, in Kelvin, supported by Night display. --> |
| <integer name="config_nightDisplayColorTemperatureMin">2596</integer> |
| <!-- Default color temperature, in Kelvin, to tint the screen when Night display is |
| activated. --> |
| <integer name="config_nightDisplayColorTemperatureDefault">2850</integer> |
| <!-- Maximum color temperature, in Kelvin, supported by Night display. --> |
| <integer name="config_nightDisplayColorTemperatureMax">4082</integer> |
| </pre> |
| <p> |
| The code is divided between framework, system services, SystemUI, and Settings: |
| </p> |
| <pre class="devsite-click-to-copy"> |
| platform/frameworks/base/core |
| ├ java/android/provider/Settings.java |
| ├ java/com/android/internal/app/NightDisplayController.java |
| └ res/res/values/config.xml |
| |
| platform/frameworks/base/proto/src/metrics_constants.proto |
| |
| platform/frameworks/base/services |
| ├ core/java/com/android/server/display/DisplayManagerService.java |
| ├ core/java/com/android/server/display/DisplayTransformManager.java |
| ├ core/java/com/android/server/display/NightDisplayService.java |
| └ java/com/android/server/SystemServer.java |
| |
| platform/frameworks/base/packages/SystemUI |
| ├ res/drawable/ic_qs_night_display_off.xml |
| ├ res/drawable/ic_qs_night_display_on.xml |
| ├ res/values/strings.xml |
| └ src/com/android/systemui/qs/tiles/NightDisplayTile.java |
| |
| platform/packages/apps/Settings |
| ├ AndroidManifest.xml |
| ├ res/drawable/ic_settings_night_display.xml |
| ├ res/values/strings.xml |
| ├ res/xml/display_settings.xml |
| ├ res/xml/night_display_settings.xml |
| ├ src/com/android/settings/Settings.java |
| ├ src/com/android/settings/dashboard/conditional/NightDisplayCondition.java |
| ├ src/com/android/settings/display/NightDisplayPreference.java |
| ├ src/com/android/settings/display/NightDisplayPreferenceController.java |
| └ src/com/android/settings/display/NightDisplaySettings.java |
| </pre> |
| |
| <h2 id="ui-features">UI features</h2> |
| <p> |
| Because Night Light is a user-facing feature, users need to be able to control |
| it. There is a full implementation of the settings in the Android Open Source |
| Project (AOSP) |
| <a href="https://android.googlesource.com/platform/packages/apps/Settings/">packages/apps/Settings</a> |
| project that device manufacturers can reference for their Settings |
| implementation. Implementers must handle the |
| <code><a href="https://developer.android.com/reference/android/provider/Settings.html#ACTION_NIGHT_DISPLAY_SETTINGS">Settings.ACTION_NIGHT_DISPLAY_SETTINGS</a></code> |
| intent to expose this setting. |
| </p> |
| <h3 id="settings">Settings</h3> |
| <p> |
| The settings for Night Light are in <em>Settings > Display > Night |
| Light</em>. From there, users can learn about Night Light, set its schedule, |
| and turn it on or off. |
| </p> |
| <ul> |
| <li><strong>Turn On Automatically</strong> |
| <ul> |
| <li><strong>Never</strong>: Night Light will never turn on automatically and |
| must be activated with the manual <strong>On / Off</strong> toggle.</li> |
| <li><strong>Custom schedule</strong>: Night Light turns on at a specified |
| <strong>Start time </strong>[default: 10:30 p.m.] and off at a specified |
| <strong>End time</strong> [default: 6:30 a.m.].</li> |
| <li><strong>Sunset to sunrise</strong>: Night Light turns on at sunset and off |
| at sunrise. The time for sunrise and sunset depends on the device location |
| and the time of year.</li> |
| </ul> |
| </li> |
| <li><strong>On / Off</strong>: Toggle that controls the current state of Night |
| Light. This state respects existing automatic rules. For example, if Night |
| Light is toggled on at 5:30 p.m. (before the automatic rule would turn it on |
| at 10:30 p.m.), Night Light will still turn off at 6:30 a.m. And if Night |
| Light is toggled off at 5:30 a.m. (before it turns off at 6:30 a.m.), it will |
| still turn on at 10:30 p.m.</li> |
| <li><strong>Intensity</strong>: |
| <a href="https://developer.android.com/reference/android/widget/SeekBar.html">Seekbar</a> |
| that controls the tint level by sliding from warm to cool. The seekbar can be |
| disabled when Night Light is not activated.</li> |
| <li><strong>Informational text</strong>: Teaches the user what Night Light does |
| and why.</li> |
| </ul> |
| <h3 id="settings-conditional">Settings conditional</h3> |
| <p> |
| Visible at the top of Settings when Night Light is on. |
| </p> |
| <h3 id="quick-settings-tile">Quick Settings tile</h3> |
| <p> |
| The Quick Settings tile behaves identically to the <strong>On / Off</strong> |
| toggle in <em>Settings > Display > Night Light</em>. |
| </p> |
| |
| </body> |
| </html> |
