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<html devsite>
<head>
<title>Implementing Night Light</title>
<meta name="project_path" value="/_project.yaml" />
<meta name="book_path" value="/_book.yaml" />
</head>
<body>
<!--
Copyright 2017 The Android Open Source Project
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
-->
<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.
</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>
</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/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.
</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>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>
|
