Hook up screen brightness knob to DisplayPowerController.

This knob is designed to effectively tune the battery saver.

Bug: 34693888
Test: FrameworksServicesTests
Change-Id: I9fd7896f59fabd9baf649cdb12f01b1baaf4c34b

core/java/android/hardware/display/DisplayManagerInternal.java

@@ -213,6 +213,10 @@ public abstract class DisplayManagerInternal {
         // If true, scales the brightness to half of desired.
         public boolean lowPowerMode;
 
+        // The factor to adjust the screen brightness in low power mode in the range
+        // 0 (screen off) to 1 (no change)
+        public float screenLowPowerBrightnessFactor;
+
         // If true, applies a brightness boost.
         public boolean boostScreenBrightness;
 
@@ -235,6 +239,7 @@ public abstract class DisplayManagerInternal {
             useProximitySensor = false;
             screenBrightness = PowerManager.BRIGHTNESS_ON;
             screenAutoBrightnessAdjustment = 0.0f;
+            screenLowPowerBrightnessFactor = 0.5f;
             useAutoBrightness = false;
             blockScreenOn = false;
             dozeScreenBrightness = PowerManager.BRIGHTNESS_DEFAULT;
@@ -258,6 +263,7 @@ public abstract class DisplayManagerInternal {
             useProximitySensor = other.useProximitySensor;
             screenBrightness = other.screenBrightness;
             screenAutoBrightnessAdjustment = other.screenAutoBrightnessAdjustment;
+            screenLowPowerBrightnessFactor = other.screenLowPowerBrightnessFactor;
             brightnessSetByUser = other.brightnessSetByUser;
             useAutoBrightness = other.useAutoBrightness;
             blockScreenOn = other.blockScreenOn;
@@ -279,6 +285,8 @@ public abstract class DisplayManagerInternal {
                     && useProximitySensor == other.useProximitySensor
                     && screenBrightness == other.screenBrightness
                     && screenAutoBrightnessAdjustment == other.screenAutoBrightnessAdjustment
+                    && screenLowPowerBrightnessFactor
+                    == other.screenLowPowerBrightnessFactor
                     && brightnessSetByUser == other.brightnessSetByUser
                     && useAutoBrightness == other.useAutoBrightness
                     && blockScreenOn == other.blockScreenOn
@@ -299,6 +307,7 @@ public abstract class DisplayManagerInternal {
                     + ", useProximitySensor=" + useProximitySensor
                     + ", screenBrightness=" + screenBrightness
                     + ", screenAutoBrightnessAdjustment=" + screenAutoBrightnessAdjustment
+                    + ", screenLowPowerBrightnessFactor=" + screenLowPowerBrightnessFactor
                     + ", brightnessSetByUser=" + brightnessSetByUser
                     + ", useAutoBrightness=" + useAutoBrightness
                     + ", blockScreenOn=" + blockScreenOn

services/core/java/com/android/server/display/DisplayPowerController.java

@@ -705,11 +705,14 @@ final class DisplayPowerController implements AutomaticBrightnessController.Call
             mAppliedDimming = false;
         }
 
-        // If low power mode is enabled, cut the brightness level by half
+        // If low power mode is enabled, scale brightness by screenLowPowerBrightnessFactor
         // as long as it is above the minimum threshold.
         if (mPowerRequest.lowPowerMode) {
             if (brightness > mScreenBrightnessRangeMinimum) {
-                brightness = Math.max(brightness / 2, mScreenBrightnessRangeMinimum);
+                final float brightnessFactor =
+                        Math.min(mPowerRequest.screenLowPowerBrightnessFactor, 1);
+                final int lowPowerBrightness = (int) (brightness * brightnessFactor);
+                brightness = Math.max(lowPowerBrightness, mScreenBrightnessRangeMinimum);
             }
             if (!mAppliedLowPower) {
                 slowChange = false;

services/core/java/com/android/server/power/PowerManagerService.java

@@ -35,7 +35,6 @@ import android.hardware.power.V1_0.PowerHint;
 import android.net.Uri;
 import android.os.BatteryManager;
 import android.os.BatteryManagerInternal;
-import android.os.PowerSaveState;
 import android.os.Binder;
 import android.os.Handler;
 import android.os.IBinder;
@@ -44,6 +43,7 @@ import android.os.Looper;
 import android.os.Message;
 import android.os.PowerManager;
 import android.os.PowerManagerInternal;
+import android.os.PowerSaveState;
 import android.os.Process;
 import android.os.RemoteException;
 import android.os.SystemClock;
@@ -69,6 +69,7 @@ import android.util.TimeUtils;
 import android.util.proto.ProtoOutputStream;
 import android.view.Display;
 import android.view.WindowManagerPolicy;
+import com.android.internal.annotations.VisibleForTesting;
 import com.android.internal.app.IAppOpsService;
 import com.android.internal.app.IBatteryStats;
 import com.android.internal.os.BackgroundThread;
@@ -628,6 +629,21 @@ public final class PowerManagerService extends SystemService
         }
     }
 
+    @VisibleForTesting
+    PowerManagerService(Context context, BatterySaverPolicy batterySaverPolicy) {
+        super(context);
+
+        mBatterySaverPolicy = batterySaverPolicy;
+        mContext = context;
+        mHandlerThread = new ServiceThread(TAG,
+                Process.THREAD_PRIORITY_DISPLAY, false /*allowIo*/);
+        mHandlerThread.start();
+        mHandler = new PowerManagerHandler(mHandlerThread.getLooper());
+        mConstants = new Constants(mHandler);
+        mDisplaySuspendBlocker = null;
+        mWakeLockSuspendBlocker = null;
+    }
+
     @Override
     public void onStart() {
         publishBinderService(Context.POWER_SERVICE, new BinderService());
@@ -2260,9 +2276,10 @@ public final class PowerManagerService extends SystemService
             mDisplayPowerRequest.brightnessSetByUser = brightnessSetByUser;
             mDisplayPowerRequest.useAutoBrightness = autoBrightness;
             mDisplayPowerRequest.useProximitySensor = shouldUseProximitySensorLocked();
-            mDisplayPowerRequest.lowPowerMode = mLowPowerModeEnabled;
             mDisplayPowerRequest.boostScreenBrightness = shouldBoostScreenBrightness();
 
+            updatePowerRequestFromBatterySaverPolicy(mDisplayPowerRequest);
+
             if (mDisplayPowerRequest.policy == DisplayPowerRequest.POLICY_DOZE) {
                 mDisplayPowerRequest.dozeScreenState = mDozeScreenStateOverrideFromDreamManager;
                 if (mDisplayPowerRequest.dozeScreenState == Display.STATE_DOZE_SUSPEND
@@ -2679,6 +2696,14 @@ public final class PowerManagerService extends SystemService
         }
     }
 
+    @VisibleForTesting
+    void updatePowerRequestFromBatterySaverPolicy(DisplayPowerRequest displayPowerRequest) {
+        PowerSaveState state = mBatterySaverPolicy.
+                getBatterySaverPolicy(ServiceType.SCREEN_BRIGHTNESS, mLowPowerModeEnabled);
+        displayPowerRequest.lowPowerMode = state.batterySaverEnabled;
+        displayPowerRequest.screenLowPowerBrightnessFactor = state.brightnessFactor;
+    }
+
     void setStayOnSettingInternal(int val) {
         Settings.Global.putInt(mContext.getContentResolver(),
                 Settings.Global.STAY_ON_WHILE_PLUGGED_IN, val);

services/tests/servicestests/src/com/android/server/power/PowerManagerServiceTest.java

@@ -0,0 +1,66 @@
+/*
+ * Copyright (C) 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.
+ */
+
+package com.android.server.power;
+
+import android.hardware.display.DisplayManagerInternal.DisplayPowerRequest;
+import android.os.PowerSaveState;
+import android.test.AndroidTestCase;
+import android.test.suitebuilder.annotation.SmallTest;
+import org.mockito.Mock;
+import org.mockito.MockitoAnnotations;
+
+import static com.google.common.truth.Truth.assertThat;
+import static org.mockito.Matchers.anyBoolean;
+import static org.mockito.Matchers.eq;
+import static org.mockito.Mockito.when;
+
+/**
+ * Tests for {@link com.android.server.power.PowerManagerService}
+ */
+public class PowerManagerServiceTest extends AndroidTestCase {
+    private static final float PRECISION = 0.001f;
+    private static final float BRIGHTNESS_FACTOR = 0.7f;
+    private static final boolean BATTERY_SAVER_ENABLED = true;
+
+    private @Mock BatterySaverPolicy mBatterySaverPolicy;
+    private PowerManagerService mService;
+    private PowerSaveState mPowerSaveState;
+    private DisplayPowerRequest mDisplayPowerRequest;
+
+    public void setUp() throws Exception {
+        super.setUp();
+        MockitoAnnotations.initMocks(this);
+
+        mPowerSaveState = new PowerSaveState.Builder()
+                .setBatterySaverEnabled(BATTERY_SAVER_ENABLED)
+                .setBrightnessFactor(BRIGHTNESS_FACTOR)
+                .build();
+        when(mBatterySaverPolicy.getBatterySaverPolicy(
+                eq(BatterySaverPolicy.ServiceType.SCREEN_BRIGHTNESS), anyBoolean()))
+                .thenReturn(mPowerSaveState);
+        mDisplayPowerRequest = new DisplayPowerRequest();
+        mService = new PowerManagerService(getContext(), mBatterySaverPolicy);
+    }
+
+    @SmallTest
+    public void testUpdatePowerScreenPolicy_UpdateDisplayPowerRequest() {
+        mService.updatePowerRequestFromBatterySaverPolicy(mDisplayPowerRequest);
+        assertThat(mDisplayPowerRequest.lowPowerMode).isEqualTo(BATTERY_SAVER_ENABLED);
+        assertThat(mDisplayPowerRequest.screenLowPowerBrightnessFactor)
+                .isWithin(PRECISION).of(BRIGHTNESS_FACTOR);
+    }
+}