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

/*
 * Copyright (C) 2012 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.display;

import android.app.ActivityManager;
import com.android.internal.app.IBatteryStats;
import com.android.server.LocalServices;
import com.android.server.am.BatteryStatsService;
import com.android.server.policy.WindowManagerPolicy;

import android.animation.Animator;
import android.animation.ObjectAnimator;
import android.annotation.Nullable;
import android.annotation.UserIdInt;
import android.content.Context;
import android.content.pm.ParceledListSlice;
import android.content.res.Resources;
import android.hardware.Sensor;
import android.hardware.SensorEvent;
import android.hardware.SensorEventListener;
import android.hardware.SensorManager;
import android.hardware.display.BrightnessChangeEvent;
import android.hardware.display.BrightnessConfiguration;
import android.hardware.display.DisplayManagerInternal.DisplayPowerCallbacks;
import android.hardware.display.DisplayManagerInternal.DisplayPowerRequest;
import android.os.Handler;
import android.os.Looper;
import android.os.Message;
import android.os.PowerManager;
import android.os.RemoteException;
import android.os.SystemClock;
import android.os.Trace;
import android.util.MathUtils;
import android.util.Slog;
import android.util.Spline;
import android.util.TimeUtils;
import android.view.Display;

import java.io.PrintWriter;

/**
 * Controls the power state of the display.
 *
 * Handles the proximity sensor, light sensor, and animations between states
 * including the screen off animation.
 *
 * This component acts independently of the rest of the power manager service.
 * In particular, it does not share any state and it only communicates
 * via asynchronous callbacks to inform the power manager that something has
 * changed.
 *
 * Everything this class does internally is serialized on its handler although
 * it may be accessed by other threads from the outside.
 *
 * Note that the power manager service guarantees that it will hold a suspend
 * blocker as long as the display is not ready.  So most of the work done here
 * does not need to worry about holding a suspend blocker unless it happens
 * independently of the display ready signal.
   *
 * For debugging, you can make the color fade and brightness animations run
 * slower by changing the "animator duration scale" option in Development Settings.
 */
final class DisplayPowerController implements AutomaticBrightnessController.Callbacks {
    private static final String TAG = "DisplayPowerController";
    private static final String SCREEN_ON_BLOCKED_TRACE_NAME = "Screen on blocked";
    private static final String SCREEN_OFF_BLOCKED_TRACE_NAME = "Screen off blocked";

    private static final boolean DEBUG = false;
    private static final boolean DEBUG_PRETEND_PROXIMITY_SENSOR_ABSENT = false;

    // If true, uses the color fade on animation.
    // We might want to turn this off if we cannot get a guarantee that the screen
    // actually turns on and starts showing new content after the call to set the
    // screen state returns.  Playing the animation can also be somewhat slow.
    private static final boolean USE_COLOR_FADE_ON_ANIMATION = false;

    // The minimum reduction in brightness when dimmed.
    private static final int SCREEN_DIM_MINIMUM_REDUCTION = 10;

    private static final int COLOR_FADE_ON_ANIMATION_DURATION_MILLIS = 250;
    private static final int COLOR_FADE_OFF_ANIMATION_DURATION_MILLIS = 400;

    private static final int MSG_UPDATE_POWER_STATE = 1;
    private static final int MSG_PROXIMITY_SENSOR_DEBOUNCED = 2;
    private static final int MSG_SCREEN_ON_UNBLOCKED = 3;
    private static final int MSG_SCREEN_OFF_UNBLOCKED = 4;
    private static final int MSG_CONFIGURE_BRIGHTNESS = 5;

    private static final int PROXIMITY_UNKNOWN = -1;
    private static final int PROXIMITY_NEGATIVE = 0;
    private static final int PROXIMITY_POSITIVE = 1;

    // Proximity sensor debounce delay in milliseconds for positive or negative transitions.
    private static final int PROXIMITY_SENSOR_POSITIVE_DEBOUNCE_DELAY = 0;
    private static final int PROXIMITY_SENSOR_NEGATIVE_DEBOUNCE_DELAY = 250;

    // Trigger proximity if distance is less than 5 cm.
    private static final float TYPICAL_PROXIMITY_THRESHOLD = 5.0f;

    // State machine constants for tracking initial brightness ramp skipping when enabled.
    private static final int RAMP_STATE_SKIP_NONE = 0;
    private static final int RAMP_STATE_SKIP_INITIAL = 1;
    private static final int RAMP_STATE_SKIP_AUTOBRIGHT = 2;

    private static final int REPORTED_TO_POLICY_SCREEN_OFF = 0;
    private static final int REPORTED_TO_POLICY_SCREEN_TURNING_ON = 1;
    private static final int REPORTED_TO_POLICY_SCREEN_ON = 2;
    private static final int REPORTED_TO_POLICY_SCREEN_TURNING_OFF = 3;

    private final Object mLock = new Object();

    private final Context mContext;

    // Our handler.
    private final DisplayControllerHandler mHandler;

    // Asynchronous callbacks into the power manager service.
    // Only invoked from the handler thread while no locks are held.
    private final DisplayPowerCallbacks mCallbacks;

    // Battery stats.
    private final IBatteryStats mBatteryStats;

    // The sensor manager.
    private final SensorManager mSensorManager;

    // The window manager policy.
    private final WindowManagerPolicy mWindowManagerPolicy;

    // The display blanker.
    private final DisplayBlanker mBlanker;

    // The proximity sensor, or null if not available or needed.
    private Sensor mProximitySensor;

    // The doze screen brightness.
    private final int mScreenBrightnessDozeConfig;

    // The dim screen brightness.
    private final int mScreenBrightnessDimConfig;

    // The minimum allowed brightness.
    private final int mScreenBrightnessRangeMinimum;

    // The maximum allowed brightness.
    private final int mScreenBrightnessRangeMaximum;

    // True if auto-brightness should be used.
    private boolean mUseSoftwareAutoBrightnessConfig;

    // True if should use light sensor to automatically determine doze screen brightness.
    private final boolean mAllowAutoBrightnessWhileDozingConfig;

    // Whether or not the color fade on screen on / off is enabled.
    private final boolean mColorFadeEnabled;

    // True if we should fade the screen while turning it off, false if we should play
    // a stylish color fade animation instead.
    private boolean mColorFadeFadesConfig;

    // True if we need to fake a transition to off when coming out of a doze state.
    // Some display hardware will blank itself when coming out of doze in order to hide
    // artifacts. For these displays we fake a transition into OFF so that policy can appropriately
    // blank itself and begin an appropriate power on animation.
    private boolean mDisplayBlanksAfterDozeConfig;

    // True if there are only buckets of brightness values when the display is in the doze state,
    // rather than a full range of values. If this is true, then we'll avoid animating the screen
    // brightness since it'd likely be multiple jarring brightness transitions instead of just one
    // to reach the final state.
    private boolean mBrightnessBucketsInDozeConfig;

    // The pending power request.
    // Initially null until the first call to requestPowerState.
    // Guarded by mLock.
    private DisplayPowerRequest mPendingRequestLocked;

    // True if a request has been made to wait for the proximity sensor to go negative.
    // Guarded by mLock.
    private boolean mPendingWaitForNegativeProximityLocked;

    // True if the pending power request or wait for negative proximity flag
    // has been changed since the last update occurred.
    // Guarded by mLock.
    private boolean mPendingRequestChangedLocked;

    // Set to true when the important parts of the pending power request have been applied.
    // The important parts are mainly the screen state.  Brightness changes may occur
    // concurrently.
    // Guarded by mLock.
    private boolean mDisplayReadyLocked;

    // Set to true if a power state update is required.
    // Guarded by mLock.
    private boolean mPendingUpdatePowerStateLocked;

    /* The following state must only be accessed by the handler thread. */

    // The currently requested power state.
    // The power controller will progressively update its internal state to match
    // the requested power state.  Initially null until the first update.
    private DisplayPowerRequest mPowerRequest;

    // The current power state.
    // Must only be accessed on the handler thread.
    private DisplayPowerState mPowerState;

    // True if the device should wait for negative proximity sensor before
    // waking up the screen.  This is set to false as soon as a negative
    // proximity sensor measurement is observed or when the device is forced to
    // go to sleep by the user.  While true, the screen remains off.
    private boolean mWaitingForNegativeProximity;

    // The actual proximity sensor threshold value.
    private float mProximityThreshold;

    // Set to true if the proximity sensor listener has been registered
    // with the sensor manager.
    private boolean mProximitySensorEnabled;

    // The debounced proximity sensor state.
    private int mProximity = PROXIMITY_UNKNOWN;

    // The raw non-debounced proximity sensor state.
    private int mPendingProximity = PROXIMITY_UNKNOWN;
    private long mPendingProximityDebounceTime = -1; // -1 if fully debounced

    // True if the screen was turned off because of the proximity sensor.
    // When the screen turns on again, we report user activity to the power manager.
    private boolean mScreenOffBecauseOfProximity;

    // The currently active screen on unblocker.  This field is non-null whenever
    // we are waiting for a callback to release it and unblock the screen.
    private ScreenOnUnblocker mPendingScreenOnUnblocker;
    private ScreenOffUnblocker mPendingScreenOffUnblocker;

    // True if we were in the process of turning off the screen.
    // This allows us to recover more gracefully from situations where we abort
    // turning off the screen.
    private boolean mPendingScreenOff;

    // True if we have unfinished business and are holding a suspend blocker.
    private boolean mUnfinishedBusiness;

    // The elapsed real time when the screen on was blocked.
    private long mScreenOnBlockStartRealTime;
    private long mScreenOffBlockStartRealTime;

    // Screen state we reported to policy. Must be one of REPORTED_TO_POLICY_SCREEN_* fields.
    private int mReportedScreenStateToPolicy;

    // If the last recorded screen state was dozing or not.
    private boolean mDozing;

    // Remembers whether certain kinds of brightness adjustments
    // were recently applied so that we can decide how to transition.
    private boolean mAppliedAutoBrightness;
    private boolean mAppliedDimming;
    private boolean mAppliedLowPower;

    // Brightness animation ramp rates in brightness units per second
    private final int mBrightnessRampRateFast;
    private final int mBrightnessRampRateSlow;

    // Whether or not to skip the initial brightness ramps into STATE_ON.
    private final boolean mSkipScreenOnBrightnessRamp;

    // A record of state for skipping brightness ramps.
    private int mSkipRampState = RAMP_STATE_SKIP_NONE;

    // The first autobrightness value set when entering RAMP_STATE_SKIP_INITIAL.
    private int mInitialAutoBrightness;

    // The controller for the automatic brightness level.
    private AutomaticBrightnessController mAutomaticBrightnessController;

    // The mapper between ambient lux, display backlight values, and display brightness.
    @Nullable
    private BrightnessMappingStrategy mBrightnessMapper;

    // The current brightness configuration.
    @Nullable
    private BrightnessConfiguration mBrightnessConfiguration;

    // The last brightness that was set by the user and not temporary. Set to -1 when a brightness
    // has yet to be recorded.
    private int mLastBrightness;

    // The last auto brightness adjustment that was set by the user and not temporary. Set to
    // Float.NaN when an auto-brightness adjustment hasn't been recorded yet.
    private float mLastAutoBrightnessAdjustment;

    // Animators.
    private ObjectAnimator mColorFadeOnAnimator;
    private ObjectAnimator mColorFadeOffAnimator;
    private RampAnimator<DisplayPowerState> mScreenBrightnessRampAnimator;

    // Tracker for brightness changes
    private final BrightnessTracker mBrightnessTracker;

    /**
     * Creates the display power controller.
     */
    public DisplayPowerController(Context context,
            DisplayPowerCallbacks callbacks, Handler handler,
            SensorManager sensorManager, DisplayBlanker blanker) {
        mHandler = new DisplayControllerHandler(handler.getLooper());
        mBrightnessTracker = new BrightnessTracker(context, null);
        mCallbacks = callbacks;

        mBatteryStats = BatteryStatsService.getService();
        mSensorManager = sensorManager;
        mWindowManagerPolicy = LocalServices.getService(WindowManagerPolicy.class);
        mBlanker = blanker;
        mContext = context;

        final Resources resources = context.getResources();
        final int screenBrightnessSettingMinimum = clampAbsoluteBrightness(resources.getInteger(
                com.android.internal.R.integer.config_screenBrightnessSettingMinimum));

        mScreenBrightnessDozeConfig = clampAbsoluteBrightness(resources.getInteger(
                com.android.internal.R.integer.config_screenBrightnessDoze));

        mScreenBrightnessDimConfig = clampAbsoluteBrightness(resources.getInteger(
                com.android.internal.R.integer.config_screenBrightnessDim));

        mScreenBrightnessRangeMinimum =
                Math.min(screenBrightnessSettingMinimum, mScreenBrightnessDimConfig);

        mScreenBrightnessRangeMaximum = clampAbsoluteBrightness(resources.getInteger(
                    com.android.internal.R.integer.config_screenBrightnessSettingMaximum));

        mUseSoftwareAutoBrightnessConfig = resources.getBoolean(
                com.android.internal.R.bool.config_automatic_brightness_available);

        mAllowAutoBrightnessWhileDozingConfig = resources.getBoolean(
                com.android.internal.R.bool.config_allowAutoBrightnessWhileDozing);

        mBrightnessRampRateFast = resources.getInteger(
                com.android.internal.R.integer.config_brightness_ramp_rate_fast);
        mBrightnessRampRateSlow = resources.getInteger(
                com.android.internal.R.integer.config_brightness_ramp_rate_slow);
        mSkipScreenOnBrightnessRamp = resources.getBoolean(
                com.android.internal.R.bool.config_skipScreenOnBrightnessRamp);

        if (mUseSoftwareAutoBrightnessConfig) {
            final float dozeScaleFactor = resources.getFraction(
                    com.android.internal.R.fraction.config_screenAutoBrightnessDozeScaleFactor,
                    1, 1);

            int[] brightLevels = resources.getIntArray(
                    com.android.internal.R.array.config_dynamicHysteresisBrightLevels);
            int[] darkLevels = resources.getIntArray(
                    com.android.internal.R.array.config_dynamicHysteresisDarkLevels);
            int[] luxHysteresisLevels = resources.getIntArray(
                    com.android.internal.R.array.config_dynamicHysteresisLuxLevels);
            HysteresisLevels dynamicHysteresis = new HysteresisLevels(
                    brightLevels, darkLevels, luxHysteresisLevels);

            long brighteningLightDebounce = resources.getInteger(
                    com.android.internal.R.integer.config_autoBrightnessBrighteningLightDebounce);
            long darkeningLightDebounce = resources.getInteger(
                    com.android.internal.R.integer.config_autoBrightnessDarkeningLightDebounce);
            boolean autoBrightnessResetAmbientLuxAfterWarmUp = resources.getBoolean(
                    com.android.internal.R.bool.config_autoBrightnessResetAmbientLuxAfterWarmUp);
            int ambientLightHorizon = resources.getInteger(
                    com.android.internal.R.integer.config_autoBrightnessAmbientLightHorizon);
            float autoBrightnessAdjustmentMaxGamma = resources.getFraction(
                    com.android.internal.R.fraction.config_autoBrightnessAdjustmentMaxGamma,
                    1, 1);

            int lightSensorWarmUpTimeConfig = resources.getInteger(
                    com.android.internal.R.integer.config_lightSensorWarmupTime);
            int lightSensorRate = resources.getInteger(
                    com.android.internal.R.integer.config_autoBrightnessLightSensorRate);
            int initialLightSensorRate = resources.getInteger(
                    com.android.internal.R.integer.config_autoBrightnessInitialLightSensorRate);
            if (initialLightSensorRate == -1) {
                initialLightSensorRate = lightSensorRate;
            } else if (initialLightSensorRate > lightSensorRate) {
                Slog.w(TAG, "Expected config_autoBrightnessInitialLightSensorRate ("
                        + initialLightSensorRate + ") to be less than or equal to "
                        + "config_autoBrightnessLightSensorRate (" + lightSensorRate + ").");
            }

            mBrightnessMapper = BrightnessMappingStrategy.create(resources);
            if (mBrightnessMapper != null) {
                mAutomaticBrightnessController = new AutomaticBrightnessController(this,
                        handler.getLooper(), sensorManager, mBrightnessMapper,
                        lightSensorWarmUpTimeConfig, mScreenBrightnessRangeMinimum,
                        mScreenBrightnessRangeMaximum, dozeScaleFactor, lightSensorRate,
                        initialLightSensorRate, brighteningLightDebounce, darkeningLightDebounce,
                        autoBrightnessResetAmbientLuxAfterWarmUp, ambientLightHorizon,
                        autoBrightnessAdjustmentMaxGamma, dynamicHysteresis);
            } else {
                mUseSoftwareAutoBrightnessConfig = false;
            }
        }

        mColorFadeEnabled = !ActivityManager.isLowRamDeviceStatic();
        mColorFadeFadesConfig = resources.getBoolean(
                com.android.internal.R.bool.config_animateScreenLights);

        mDisplayBlanksAfterDozeConfig = resources.getBoolean(
                com.android.internal.R.bool.config_displayBlanksAfterDoze);

        mBrightnessBucketsInDozeConfig = resources.getBoolean(
                com.android.internal.R.bool.config_displayBrightnessBucketsInDoze);

        if (!DEBUG_PRETEND_PROXIMITY_SENSOR_ABSENT) {
            mProximitySensor = mSensorManager.getDefaultSensor(Sensor.TYPE_PROXIMITY);
            if (mProximitySensor != null) {
                mProximityThreshold = Math.min(mProximitySensor.getMaximumRange(),
                        TYPICAL_PROXIMITY_THRESHOLD);
            }
        }

        mLastBrightness = -1;
        mLastAutoBrightnessAdjustment = Float.NaN;
    }

    /**
     * Returns true if the proximity sensor screen-off function is available.
     */
    public boolean isProximitySensorAvailable() {
        return mProximitySensor != null;
    }

    /**
     * Get the {@link BrightnessChangeEvent}s for the specified user.
     * @param userId userId to fetch data for
     * @param includePackage if false will null out the package name in events
     */
    public ParceledListSlice<BrightnessChangeEvent> getBrightnessEvents(
            @UserIdInt int userId, boolean includePackage) {
        return mBrightnessTracker.getEvents(userId, includePackage);
    }

    /**
     * Persist the brightness slider events to disk.
     */
    public void persistBrightnessSliderEvents() {
        mBrightnessTracker.persistEvents();
    }

    /**
     * Requests a new power state.
     * The controller makes a copy of the provided object and then
     * begins adjusting the power state to match what was requested.
     *
     * @param request The requested power state.
     * @param waitForNegativeProximity If true, issues a request to wait for
     * negative proximity before turning the screen back on, assuming the screen
     * was turned off by the proximity sensor.
     * @return True if display is ready, false if there are important changes that must
     * be made asynchronously (such as turning the screen on), in which case the caller
     * should grab a wake lock, watch for {@link DisplayPowerCallbacks#onStateChanged()}
     * then try the request again later until the state converges.
     */
    public boolean requestPowerState(DisplayPowerRequest request,
            boolean waitForNegativeProximity) {
        if (DEBUG) {
            Slog.d(TAG, "requestPowerState: "
                    + request + ", waitForNegativeProximity=" + waitForNegativeProximity);
        }

        synchronized (mLock) {
            boolean changed = false;

            if (waitForNegativeProximity
                    && !mPendingWaitForNegativeProximityLocked) {
                mPendingWaitForNegativeProximityLocked = true;
                changed = true;
            }

            if (mPendingRequestLocked == null) {
                mPendingRequestLocked = new DisplayPowerRequest(request);
                changed = true;
            } else if (!mPendingRequestLocked.equals(request)) {
                mPendingRequestLocked.copyFrom(request);
                changed = true;
            }

            if (changed) {
                mDisplayReadyLocked = false;
            }

            if (changed && !mPendingRequestChangedLocked) {
                mPendingRequestChangedLocked = true;
                sendUpdatePowerStateLocked();
            }

            return mDisplayReadyLocked;
        }
    }

    private void sendUpdatePowerState() {
        synchronized (mLock) {
            sendUpdatePowerStateLocked();
        }
    }

    private void sendUpdatePowerStateLocked() {
        if (!mPendingUpdatePowerStateLocked) {
            mPendingUpdatePowerStateLocked = true;
            Message msg = mHandler.obtainMessage(MSG_UPDATE_POWER_STATE);
            mHandler.sendMessage(msg);
        }
    }

    private void initialize() {
        // Initialize the power state object for the default display.
        // In the future, we might manage multiple displays independently.
        mPowerState = new DisplayPowerState(mBlanker,
                mColorFadeEnabled ? new ColorFade(Display.DEFAULT_DISPLAY) : null);

        if (mColorFadeEnabled) {
            mColorFadeOnAnimator = ObjectAnimator.ofFloat(
                    mPowerState, DisplayPowerState.COLOR_FADE_LEVEL, 0.0f, 1.0f);
            mColorFadeOnAnimator.setDuration(COLOR_FADE_ON_ANIMATION_DURATION_MILLIS);
            mColorFadeOnAnimator.addListener(mAnimatorListener);

            mColorFadeOffAnimator = ObjectAnimator.ofFloat(
                    mPowerState, DisplayPowerState.COLOR_FADE_LEVEL, 1.0f, 0.0f);
            mColorFadeOffAnimator.setDuration(COLOR_FADE_OFF_ANIMATION_DURATION_MILLIS);
            mColorFadeOffAnimator.addListener(mAnimatorListener);
        }

        mScreenBrightnessRampAnimator = new RampAnimator<DisplayPowerState>(
                mPowerState, DisplayPowerState.SCREEN_BRIGHTNESS);
        mScreenBrightnessRampAnimator.setListener(mRampAnimatorListener);

        // Initialize screen state for battery stats.
        try {
            mBatteryStats.noteScreenState(mPowerState.getScreenState());
            mBatteryStats.noteScreenBrightness(mPowerState.getScreenBrightness());
        } catch (RemoteException ex) {
            // same process
        }

        // Initialize all of the brightness tracking state
        final float brightness = getNits(mPowerState.getScreenBrightness());
        if (brightness >= 0.0f) {
            mBrightnessTracker.start(brightness);
        }
    }

    private final Animator.AnimatorListener mAnimatorListener = new Animator.AnimatorListener() {
        @Override
        public void onAnimationStart(Animator animation) {
        }
        @Override
        public void onAnimationEnd(Animator animation) {
            sendUpdatePowerState();
        }
        @Override
        public void onAnimationRepeat(Animator animation) {
        }
        @Override
        public void onAnimationCancel(Animator animation) {
        }
    };

    private final RampAnimator.Listener mRampAnimatorListener = new RampAnimator.Listener() {
        @Override
        public void onAnimationEnd() {
            sendUpdatePowerState();
        }
    };

    private void updatePowerState() {
        // Update the power state request.
        final boolean mustNotify;
        boolean mustInitialize = false;
        boolean autoBrightnessAdjustmentChanged = false;

        synchronized (mLock) {
            mPendingUpdatePowerStateLocked = false;
            if (mPendingRequestLocked == null) {
                return; // wait until first actual power request
            }

            if (mPowerRequest == null) {
                mPowerRequest = new DisplayPowerRequest(mPendingRequestLocked);
                mWaitingForNegativeProximity = mPendingWaitForNegativeProximityLocked;
                mPendingWaitForNegativeProximityLocked = false;
                mPendingRequestChangedLocked = false;
                mustInitialize = true;
            } else if (mPendingRequestChangedLocked) {
                autoBrightnessAdjustmentChanged = (mPowerRequest.screenAutoBrightnessAdjustment
                        != mPendingRequestLocked.screenAutoBrightnessAdjustment);
                mPowerRequest.copyFrom(mPendingRequestLocked);
                mWaitingForNegativeProximity |= mPendingWaitForNegativeProximityLocked;
                mPendingWaitForNegativeProximityLocked = false;
                mPendingRequestChangedLocked = false;
                mDisplayReadyLocked = false;
            }

            mustNotify = !mDisplayReadyLocked;
        }

        // Initialize things the first time the power state is changed.
        if (mustInitialize) {
            initialize();
        }

        // Compute the basic display state using the policy.
        // We might override this below based on other factors.
        int state;
        int brightness = PowerManager.BRIGHTNESS_DEFAULT;
        boolean performScreenOffTransition = false;
        switch (mPowerRequest.policy) {
            case DisplayPowerRequest.POLICY_OFF:
                state = Display.STATE_OFF;
                performScreenOffTransition = true;
                break;
            case DisplayPowerRequest.POLICY_DOZE:
                if (mPowerRequest.dozeScreenState != Display.STATE_UNKNOWN) {
                    state = mPowerRequest.dozeScreenState;
                } else {
                    state = Display.STATE_DOZE;
                }
                if (!mAllowAutoBrightnessWhileDozingConfig) {
                    brightness = mPowerRequest.dozeScreenBrightness;
                }
                break;
            case DisplayPowerRequest.POLICY_VR:
                state = Display.STATE_VR;
                break;
            case DisplayPowerRequest.POLICY_DIM:
            case DisplayPowerRequest.POLICY_BRIGHT:
            default:
                state = Display.STATE_ON;
                break;
        }
        assert(state != Display.STATE_UNKNOWN);

        // Apply the proximity sensor.
        if (mProximitySensor != null) {
            if (mPowerRequest.useProximitySensor && state != Display.STATE_OFF) {
                setProximitySensorEnabled(true);
                if (!mScreenOffBecauseOfProximity
                        && mProximity == PROXIMITY_POSITIVE) {
                    mScreenOffBecauseOfProximity = true;
                    sendOnProximityPositiveWithWakelock();
                }
            } else if (mWaitingForNegativeProximity
                    && mScreenOffBecauseOfProximity
                    && mProximity == PROXIMITY_POSITIVE
                    && state != Display.STATE_OFF) {
                setProximitySensorEnabled(true);
            } else {
                setProximitySensorEnabled(false);
                mWaitingForNegativeProximity = false;
            }
            if (mScreenOffBecauseOfProximity
                    && mProximity != PROXIMITY_POSITIVE) {
                mScreenOffBecauseOfProximity = false;
                sendOnProximityNegativeWithWakelock();
            }
        } else {
            mWaitingForNegativeProximity = false;
        }
        if (mScreenOffBecauseOfProximity) {
            state = Display.STATE_OFF;
        }

        // Animate the screen state change unless already animating.
        // The transition may be deferred, so after this point we will use the
        // actual state instead of the desired one.
        final int oldState = mPowerState.getScreenState();
        animateScreenStateChange(state, performScreenOffTransition);
        state = mPowerState.getScreenState();

        // Use zero brightness when screen is off.
        if (state == Display.STATE_OFF) {
            brightness = PowerManager.BRIGHTNESS_OFF;
        }


        final boolean autoBrightnessEnabledInDoze =
                mAllowAutoBrightnessWhileDozingConfig && Display.isDozeState(state);
        final boolean autoBrightnessEnabled = mPowerRequest.useAutoBrightness
                    && (state == Display.STATE_ON || autoBrightnessEnabledInDoze)
                    && brightness < 0
                    && mAutomaticBrightnessController != null;
        final boolean brightnessAdjustmentChanged =
                !Float.isNaN(mLastAutoBrightnessAdjustment)
                && mPowerRequest.screenAutoBrightnessAdjustment != mLastAutoBrightnessAdjustment;
        final boolean brightnessChanged = mLastBrightness >= 0
                && mPowerRequest.screenBrightness != mLastBrightness;

        // Update the last set brightness values.
        final boolean userInitiatedChange;
        if (mPowerRequest.brightnessSetByUser && !mPowerRequest.brightnessIsTemporary) {
            userInitiatedChange = autoBrightnessEnabled && brightnessAdjustmentChanged
                    || !autoBrightnessEnabled && brightnessChanged;
            mLastBrightness = mPowerRequest.screenBrightness;
            mLastAutoBrightnessAdjustment = mPowerRequest.screenAutoBrightnessAdjustment;
        } else {
            userInitiatedChange = false;
        }

        // Configure auto-brightness.
        if (mAutomaticBrightnessController != null) {
            mAutomaticBrightnessController.configure(autoBrightnessEnabled,
                    mBrightnessConfiguration, mPowerRequest.screenAutoBrightnessAdjustment,
                    state != Display.STATE_ON, userInitiatedChange);
        }

        // Apply brightness boost.
        // We do this here after configuring auto-brightness so that we don't
        // disable the light sensor during this temporary state.  That way when
        // boost ends we will be able to resume normal auto-brightness behavior
        // without any delay.
        if (mPowerRequest.boostScreenBrightness
                && brightness != PowerManager.BRIGHTNESS_OFF) {
            brightness = PowerManager.BRIGHTNESS_ON;
        }

        // Apply auto-brightness.
        boolean slowChange = false;
        if (brightness < 0) {
            if (autoBrightnessEnabled) {
                brightness = mAutomaticBrightnessController.getAutomaticScreenBrightness();
            }
            if (brightness >= 0) {
                // Use current auto-brightness value and slowly adjust to changes.
                brightness = clampScreenBrightness(brightness);
                if (mAppliedAutoBrightness && !autoBrightnessAdjustmentChanged) {
                    slowChange = true; // slowly adapt to auto-brightness
                }
                mAppliedAutoBrightness = true;
            } else {
                mAppliedAutoBrightness = false;
            }
        } else {
            mAppliedAutoBrightness = false;
        }

        // Use default brightness when dozing unless overridden.
        if (brightness < 0 && Display.isDozeState(state)) {
            brightness = mScreenBrightnessDozeConfig;
        }

        // Apply manual brightness.
        // Use the current brightness setting from the request, which is expected
        // provide a nominal default value for the case where auto-brightness
        // is not ready yet.
        if (brightness < 0) {
            brightness = clampScreenBrightness(mPowerRequest.screenBrightness);
        }

        // Apply dimming by at least some minimum amount when user activity
        // timeout is about to expire.
        if (mPowerRequest.policy == DisplayPowerRequest.POLICY_DIM) {
            if (brightness > mScreenBrightnessRangeMinimum) {
                brightness = Math.max(Math.min(brightness - SCREEN_DIM_MINIMUM_REDUCTION,
                        mScreenBrightnessDimConfig), mScreenBrightnessRangeMinimum);
            }
            if (!mAppliedDimming) {
                slowChange = false;
            }
            mAppliedDimming = true;
        } else if (mAppliedDimming) {
            slowChange = false;
            mAppliedDimming = false;
        }

        // 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) {
                final float brightnessFactor =
                        Math.min(mPowerRequest.screenLowPowerBrightnessFactor, 1);
                final int lowPowerBrightness = (int) (brightness * brightnessFactor);
                brightness = Math.max(lowPowerBrightness, mScreenBrightnessRangeMinimum);
            }
            if (!mAppliedLowPower) {
                slowChange = false;
            }
            mAppliedLowPower = true;
        } else if (mAppliedLowPower) {
            slowChange = false;
            mAppliedLowPower = false;
        }

        // Animate the screen brightness when the screen is on or dozing.
        // Skip the animation when the screen is off or suspended or transition to/from VR.
        if (!mPendingScreenOff) {
            if (mSkipScreenOnBrightnessRamp) {
                if (state == Display.STATE_ON) {
                    if (mSkipRampState == RAMP_STATE_SKIP_NONE && mDozing) {
                        mInitialAutoBrightness = brightness;
                        mSkipRampState = RAMP_STATE_SKIP_INITIAL;
                    } else if (mSkipRampState == RAMP_STATE_SKIP_INITIAL
                            && mUseSoftwareAutoBrightnessConfig
                            && brightness != mInitialAutoBrightness) {
                        mSkipRampState = RAMP_STATE_SKIP_AUTOBRIGHT;
                    } else if (mSkipRampState == RAMP_STATE_SKIP_AUTOBRIGHT) {
                        mSkipRampState = RAMP_STATE_SKIP_NONE;
                    }
                } else {
                    mSkipRampState = RAMP_STATE_SKIP_NONE;
                }
            }

            final boolean wasOrWillBeInVr =
                    (state == Display.STATE_VR || oldState == Display.STATE_VR);
            final boolean initialRampSkip =
                    state == Display.STATE_ON && mSkipRampState != RAMP_STATE_SKIP_NONE;
            // While dozing, sometimes the brightness is split into buckets. Rather than animating
            // through the buckets, which is unlikely to be smooth in the first place, just jump
            // right to the suggested brightness.
            final boolean hasBrightnessBuckets =
                    Display.isDozeState(state) && mBrightnessBucketsInDozeConfig;
            // If the color fade is totally covering the screen then we can change the backlight
            // level without it being a noticeable jump since any actual content isn't yet visible.
            final boolean isDisplayContentVisible =
                    mColorFadeEnabled && mPowerState.getColorFadeLevel() == 1.0f;
            if (initialRampSkip || hasBrightnessBuckets
                    || wasOrWillBeInVr || !isDisplayContentVisible) {
                animateScreenBrightness(brightness, 0);
            } else {
                animateScreenBrightness(brightness,
                        slowChange ? mBrightnessRampRateSlow : mBrightnessRampRateFast);
            }

            final float brightnessInNits = getNits(brightness);
            if (!mPowerRequest.brightnessIsTemporary && brightnessInNits >= 0.0f) {
                // We only want to track changes made by the user and on devices that can actually
                // map the display backlight values into a physical brightness unit.
                mBrightnessTracker.notifyBrightnessChanged(brightnessInNits, userInitiatedChange);
            }
        }

        // Determine whether the display is ready for use in the newly requested state.
        // Note that we do not wait for the brightness ramp animation to complete before
        // reporting the display is ready because we only need to ensure the screen is in the
        // right power state even as it continues to converge on the desired brightness.
        final boolean ready = mPendingScreenOnUnblocker == null &&
                (!mColorFadeEnabled ||
                        (!mColorFadeOnAnimator.isStarted() && !mColorFadeOffAnimator.isStarted()))
                && mPowerState.waitUntilClean(mCleanListener);
        final boolean finished = ready
                && !mScreenBrightnessRampAnimator.isAnimating();

        // Notify policy about screen turned on.
        if (ready && state != Display.STATE_OFF
                && mReportedScreenStateToPolicy == REPORTED_TO_POLICY_SCREEN_TURNING_ON) {
            setReportedScreenState(REPORTED_TO_POLICY_SCREEN_ON);
            mWindowManagerPolicy.screenTurnedOn();
        }

        // Grab a wake lock if we have unfinished business.
        if (!finished && !mUnfinishedBusiness) {
            if (DEBUG) {
                Slog.d(TAG, "Unfinished business...");
            }
            mCallbacks.acquireSuspendBlocker();
            mUnfinishedBusiness = true;
        }

        // Notify the power manager when ready.
        if (ready && mustNotify) {
            // Send state change.
            synchronized (mLock) {
                if (!mPendingRequestChangedLocked) {
                    mDisplayReadyLocked = true;

                    if (DEBUG) {
                        Slog.d(TAG, "Display ready!");
                    }
                }
            }
            sendOnStateChangedWithWakelock();
        }

        // Release the wake lock when we have no unfinished business.
        if (finished && mUnfinishedBusiness) {
            if (DEBUG) {
                Slog.d(TAG, "Finished business...");
            }
            mUnfinishedBusiness = false;
            mCallbacks.releaseSuspendBlocker();
        }

        // Record if dozing for future comparison.
        mDozing = state != Display.STATE_ON;
    }

    @Override
    public void updateBrightness() {
        sendUpdatePowerState();
    }

    public void setBrightnessConfiguration(BrightnessConfiguration c) {
        Message msg = mHandler.obtainMessage(MSG_CONFIGURE_BRIGHTNESS, c);
        msg.sendToTarget();
    }

    private void blockScreenOn() {
        if (mPendingScreenOnUnblocker == null) {
            Trace.asyncTraceBegin(Trace.TRACE_TAG_POWER, SCREEN_ON_BLOCKED_TRACE_NAME, 0);
            mPendingScreenOnUnblocker = new ScreenOnUnblocker();
            mScreenOnBlockStartRealTime = SystemClock.elapsedRealtime();
            Slog.i(TAG, "Blocking screen on until initial contents have been drawn.");
        }
    }

    private void unblockScreenOn() {
        if (mPendingScreenOnUnblocker != null) {
            mPendingScreenOnUnblocker = null;
            long delay = SystemClock.elapsedRealtime() - mScreenOnBlockStartRealTime;
            Slog.i(TAG, "Unblocked screen on after " + delay + " ms");
            Trace.asyncTraceEnd(Trace.TRACE_TAG_POWER, SCREEN_ON_BLOCKED_TRACE_NAME, 0);
        }
    }

    private void blockScreenOff() {
        if (mPendingScreenOffUnblocker == null) {
            Trace.asyncTraceBegin(Trace.TRACE_TAG_POWER, SCREEN_OFF_BLOCKED_TRACE_NAME, 0);
            mPendingScreenOffUnblocker = new ScreenOffUnblocker();
            mScreenOffBlockStartRealTime = SystemClock.elapsedRealtime();
            Slog.i(TAG, "Blocking screen off");
        }
    }

    private void unblockScreenOff() {
        if (mPendingScreenOffUnblocker != null) {
            mPendingScreenOffUnblocker = null;
            long delay = SystemClock.elapsedRealtime() - mScreenOffBlockStartRealTime;
            Slog.i(TAG, "Unblocked screen off after " + delay + " ms");
            Trace.asyncTraceEnd(Trace.TRACE_TAG_POWER, SCREEN_OFF_BLOCKED_TRACE_NAME, 0);
        }
    }

    private boolean setScreenState(int state) {
        return setScreenState(state, false /*reportOnly*/);
    }

    private boolean setScreenState(int state, boolean reportOnly) {
        final boolean isOff = (state == Display.STATE_OFF);
        if (mPowerState.getScreenState() != state) {

            // If we are trying to turn screen off, give policy a chance to do something before we
            // actually turn the screen off.
            if (isOff && !mScreenOffBecauseOfProximity) {
                if (mReportedScreenStateToPolicy == REPORTED_TO_POLICY_SCREEN_ON) {
                    setReportedScreenState(REPORTED_TO_POLICY_SCREEN_TURNING_OFF);
                    blockScreenOff();
                    mWindowManagerPolicy.screenTurningOff(mPendingScreenOffUnblocker);
                    unblockScreenOff();
                } else if (mPendingScreenOffUnblocker != null) {
                    // Abort doing the state change until screen off is unblocked.
                    return false;
                }
            }

            if (!reportOnly) {
                Trace.traceCounter(Trace.TRACE_TAG_POWER, "ScreenState", state);
                mPowerState.setScreenState(state);
                // Tell battery stats about the transition.
                try {
                    mBatteryStats.noteScreenState(state);
                } catch (RemoteException ex) {
                    // same process
                }
            }
        }

        // Tell the window manager policy when the screen is turned off or on unless it's due
        // to the proximity sensor.  We temporarily block turning the screen on until the
        // window manager is ready by leaving a black surface covering the screen.
        // This surface is essentially the final state of the color fade animation and
        // it is only removed once the window manager tells us that the activity has
        // finished drawing underneath.
        if (isOff && mReportedScreenStateToPolicy != REPORTED_TO_POLICY_SCREEN_OFF
                && !mScreenOffBecauseOfProximity) {
            setReportedScreenState(REPORTED_TO_POLICY_SCREEN_OFF);
            unblockScreenOn();
            mWindowManagerPolicy.screenTurnedOff();
        } else if (!isOff
                && mReportedScreenStateToPolicy == REPORTED_TO_POLICY_SCREEN_TURNING_OFF) {

            // We told policy already that screen was turning off, but now we changed our minds.
            // Complete the full state transition on -> turningOff -> off.
            unblockScreenOff();
            mWindowManagerPolicy.screenTurnedOff();
            setReportedScreenState(REPORTED_TO_POLICY_SCREEN_OFF);
        }
        if (!isOff && mReportedScreenStateToPolicy == REPORTED_TO_POLICY_SCREEN_OFF) {
            setReportedScreenState(REPORTED_TO_POLICY_SCREEN_TURNING_ON);
            if (mPowerState.getColorFadeLevel() == 0.0f) {
                blockScreenOn();
            } else {
                unblockScreenOn();
            }
            mWindowManagerPolicy.screenTurningOn(mPendingScreenOnUnblocker);
        }

        // Return true if the screen isn't blocked.
        return mPendingScreenOnUnblocker == null;
    }

    private void setReportedScreenState(int state) {
        Trace.traceCounter(Trace.TRACE_TAG_POWER, "ReportedScreenStateToPolicy", state);
        mReportedScreenStateToPolicy = state;
    }

    private int clampScreenBrightness(int value) {
        return MathUtils.constrain(
                value, mScreenBrightnessRangeMinimum, mScreenBrightnessRangeMaximum);
    }

    private void animateScreenBrightness(int target, int rate) {
        if (DEBUG) {
            Slog.d(TAG, "Animating brightness: target=" + target +", rate=" + rate);
        }
        if (mScreenBrightnessRampAnimator.animateTo(target, rate)) {
            Trace.traceCounter(Trace.TRACE_TAG_POWER, "TargetScreenBrightness", target);
            try {
                mBatteryStats.noteScreenBrightness(target);
            } catch (RemoteException ex) {
                // same process
            }
        }
    }

    private void animateScreenStateChange(int target, boolean performScreenOffTransition) {
        // If there is already an animation in progress, don't interfere with it.
        if (mColorFadeEnabled &&
                (mColorFadeOnAnimator.isStarted() || mColorFadeOffAnimator.isStarted())) {
            if (target != Display.STATE_ON) {
                return;
            }
            // If display state changed to on, proceed and stop the color fade and turn screen on.
            mPendingScreenOff = false;
        }

        if (mDisplayBlanksAfterDozeConfig
                && Display.isDozeState(mPowerState.getScreenState())
                && !Display.isDozeState(target)) {
            // Skip the screen off animation and add a black surface to hide the
            // contents of the screen.
            mPowerState.prepareColorFade(mContext,
                    mColorFadeFadesConfig ? ColorFade.MODE_FADE : ColorFade.MODE_WARM_UP);
            if (mColorFadeOffAnimator != null) {
                mColorFadeOffAnimator.end();
            }
            // Some display hardware will blank itself on the transition between doze and non-doze
            // but still on display states. In this case we want to report to policy that the
            // display has turned off so it can prepare the appropriate power on animation, but we
            // don't want to actually transition to the fully off state since that takes
            // significantly longer to transition from.
            setScreenState(Display.STATE_OFF, target != Display.STATE_OFF /*reportOnly*/);
        }

        // If we were in the process of turning off the screen but didn't quite
        // finish.  Then finish up now to prevent a jarring transition back
        // to screen on if we skipped blocking screen on as usual.
        if (mPendingScreenOff && target != Display.STATE_OFF) {
            setScreenState(Display.STATE_OFF);
            mPendingScreenOff = false;
            mPowerState.dismissColorFadeResources();
        }

        if (target == Display.STATE_ON) {
            // Want screen on.  The contents of the screen may not yet
            // be visible if the color fade has not been dismissed because
            // its last frame of animation is solid black.
            if (!setScreenState(Display.STATE_ON)) {
                return; // screen on blocked
            }
            if (USE_COLOR_FADE_ON_ANIMATION && mColorFadeEnabled && mPowerRequest.isBrightOrDim()) {
                // Perform screen on animation.
                if (mPowerState.getColorFadeLevel() == 1.0f) {
                    mPowerState.dismissColorFade();
                } else if (mPowerState.prepareColorFade(mContext,
                        mColorFadeFadesConfig ?
                                ColorFade.MODE_FADE :
                                        ColorFade.MODE_WARM_UP)) {
                    mColorFadeOnAnimator.start();
                } else {
                    mColorFadeOnAnimator.end();
                }
            } else {
                // Skip screen on animation.
                mPowerState.setColorFadeLevel(1.0f);
                mPowerState.dismissColorFade();
            }
        } else if (target == Display.STATE_VR) {
            // Wait for brightness animation to complete beforehand when entering VR
            // from screen on to prevent a perceptible jump because brightness may operate
            // differently when the display is configured for dozing.
            if (mScreenBrightnessRampAnimator.isAnimating()
                    && mPowerState.getScreenState() == Display.STATE_ON) {
                return;
            }

            // Set screen state.
            if (!setScreenState(Display.STATE_VR)) {
                return; // screen on blocked
            }

            // Dismiss the black surface without fanfare.
            mPowerState.setColorFadeLevel(1.0f);
            mPowerState.dismissColorFade();
        } else if (target == Display.STATE_DOZE) {
            // Want screen dozing.
            // Wait for brightness animation to complete beforehand when entering doze
            // from screen on to prevent a perceptible jump because brightness may operate
            // differently when the display is configured for dozing.
            if (mScreenBrightnessRampAnimator.isAnimating()
                    && mPowerState.getScreenState() == Display.STATE_ON) {
                return;
            }

            // Set screen state.
            if (!setScreenState(Display.STATE_DOZE)) {
                return; // screen on blocked
            }

            // Dismiss the black surface without fanfare.
            mPowerState.setColorFadeLevel(1.0f);
            mPowerState.dismissColorFade();
        } else if (target == Display.STATE_DOZE_SUSPEND) {
            // Want screen dozing and suspended.
            // Wait for brightness animation to complete beforehand unless already
            // suspended because we may not be able to change it after suspension.
            if (mScreenBrightnessRampAnimator.isAnimating()
                    && mPowerState.getScreenState() != Display.STATE_DOZE_SUSPEND) {
                return;
            }

            // If not already suspending, temporarily set the state to doze until the
            // screen on is unblocked, then suspend.
            if (mPowerState.getScreenState() != Display.STATE_DOZE_SUSPEND) {
                if (!setScreenState(Display.STATE_DOZE)) {
                    return; // screen on blocked
                }
                setScreenState(Display.STATE_DOZE_SUSPEND); // already on so can't block
            }

            // Dismiss the black surface without fanfare.
            mPowerState.setColorFadeLevel(1.0f);
            mPowerState.dismissColorFade();
        } else if (target == Display.STATE_ON_SUSPEND) {
            // Want screen full-power and suspended.
            // Wait for brightness animation to complete beforehand unless already
            // suspended because we may not be able to change it after suspension.
            if (mScreenBrightnessRampAnimator.isAnimating()
                    && mPowerState.getScreenState() != Display.STATE_ON_SUSPEND) {
                return;
            }

            // If not already suspending, temporarily set the state to on until the
            // screen on is unblocked, then suspend.
            if (mPowerState.getScreenState() != Display.STATE_ON_SUSPEND) {
                if (!setScreenState(Display.STATE_ON)) {
                    return;
                }
                setScreenState(Display.STATE_ON_SUSPEND);
            }

            // Dismiss the black surface without fanfare.
            mPowerState.setColorFadeLevel(1.0f);
            mPowerState.dismissColorFade();
        } else {
            // Want screen off.
            mPendingScreenOff = true;
            if (!mColorFadeEnabled) {
                mPowerState.setColorFadeLevel(0.0f);
            }

            if (mPowerState.getColorFadeLevel() == 0.0f) {
                // Turn the screen off.
                // A black surface is already hiding the contents of the screen.
                setScreenState(Display.STATE_OFF);
                mPendingScreenOff = false;
                mPowerState.dismissColorFadeResources();
            } else if (performScreenOffTransition
                    && mPowerState.prepareColorFade(mContext,
                            mColorFadeFadesConfig ?
                                    ColorFade.MODE_FADE : ColorFade.MODE_COOL_DOWN)
                    && mPowerState.getScreenState() != Display.STATE_OFF) {
                // Perform the screen off animation.
                mColorFadeOffAnimator.start();
            } else {
                // Skip the screen off animation and add a black surface to hide the
                // contents of the screen.
                mColorFadeOffAnimator.end();
            }
        }
    }

    private final Runnable mCleanListener = new Runnable() {
        @Override
        public void run() {
            sendUpdatePowerState();
        }
    };

    private void setProximitySensorEnabled(boolean enable) {
        if (enable) {
            if (!mProximitySensorEnabled) {
                // Register the listener.
                // Proximity sensor state already cleared initially.
                mProximitySensorEnabled = true;
                mSensorManager.registerListener(mProximitySensorListener, mProximitySensor,
                        SensorManager.SENSOR_DELAY_NORMAL, mHandler);
            }
        } else {
            if (mProximitySensorEnabled) {
                // Unregister the listener.
                // Clear the proximity sensor state for next time.
                mProximitySensorEnabled = false;
                mProximity = PROXIMITY_UNKNOWN;
                mPendingProximity = PROXIMITY_UNKNOWN;
                mHandler.removeMessages(MSG_PROXIMITY_SENSOR_DEBOUNCED);
                mSensorManager.unregisterListener(mProximitySensorListener);
                clearPendingProximityDebounceTime(); // release wake lock (must be last)
            }
        }
    }

    private void handleProximitySensorEvent(long time, boolean positive) {
        if (mProximitySensorEnabled) {
            if (mPendingProximity == PROXIMITY_NEGATIVE && !positive) {
                return; // no change
            }
            if (mPendingProximity == PROXIMITY_POSITIVE && positive) {
                return; // no change
            }

            // Only accept a proximity sensor reading if it remains
            // stable for the entire debounce delay.  We hold a wake lock while
            // debouncing the sensor.
            mHandler.removeMessages(MSG_PROXIMITY_SENSOR_DEBOUNCED);
            if (positive) {
                mPendingProximity = PROXIMITY_POSITIVE;
                setPendingProximityDebounceTime(
                        time + PROXIMITY_SENSOR_POSITIVE_DEBOUNCE_DELAY); // acquire wake lock
            } else {
                mPendingProximity = PROXIMITY_NEGATIVE;
                setPendingProximityDebounceTime(
                        time + PROXIMITY_SENSOR_NEGATIVE_DEBOUNCE_DELAY); // acquire wake lock
            }

            // Debounce the new sensor reading.
            debounceProximitySensor();
        }
    }

    private void debounceProximitySensor() {
        if (mProximitySensorEnabled
                && mPendingProximity != PROXIMITY_UNKNOWN
                && mPendingProximityDebounceTime >= 0) {
            final long now = SystemClock.uptimeMillis();
            if (mPendingProximityDebounceTime <= now) {
                // Sensor reading accepted.  Apply the change then release the wake lock.
                mProximity = mPendingProximity;
                updatePowerState();
                clearPendingProximityDebounceTime(); // release wake lock (must be last)
            } else {
                // Need to wait a little longer.
                // Debounce again later.  We continue holding a wake lock while waiting.
                Message msg = mHandler.obtainMessage(MSG_PROXIMITY_SENSOR_DEBOUNCED);
                mHandler.sendMessageAtTime(msg, mPendingProximityDebounceTime);
            }
        }
    }

    private void clearPendingProximityDebounceTime() {
        if (mPendingProximityDebounceTime >= 0) {
            mPendingProximityDebounceTime = -1;
            mCallbacks.releaseSuspendBlocker(); // release wake lock
        }
    }

    private void setPendingProximityDebounceTime(long debounceTime) {
        if (mPendingProximityDebounceTime < 0) {
            mCallbacks.acquireSuspendBlocker(); // acquire wake lock
        }
        mPendingProximityDebounceTime = debounceTime;
    }

    private void sendOnStateChangedWithWakelock() {
        mCallbacks.acquireSuspendBlocker();
        mHandler.post(mOnStateChangedRunnable);
    }

    private float getNits(int backlight) {
        if (mBrightnessMapper != null) {
            return mBrightnessMapper.getNits(backlight);
        } else {
            return -1.0f;
        }
    }

    private final Runnable mOnStateChangedRunnable = new Runnable() {
        @Override
        public void run() {
            mCallbacks.onStateChanged();
            mCallbacks.releaseSuspendBlocker();
        }
    };

    private void sendOnProximityPositiveWithWakelock() {
        mCallbacks.acquireSuspendBlocker();
        mHandler.post(mOnProximityPositiveRunnable);
    }

    private final Runnable mOnProximityPositiveRunnable = new Runnable() {
        @Override
        public void run() {
            mCallbacks.onProximityPositive();
            mCallbacks.releaseSuspendBlocker();
        }
    };

    private void sendOnProximityNegativeWithWakelock() {
        mCallbacks.acquireSuspendBlocker();
        mHandler.post(mOnProximityNegativeRunnable);
    }

    private final Runnable mOnProximityNegativeRunnable = new Runnable() {
        @Override
        public void run() {
            mCallbacks.onProximityNegative();
            mCallbacks.releaseSuspendBlocker();
        }
    };

    public void dump(final PrintWriter pw) {
        synchronized (mLock) {
            pw.println();
            pw.println("Display Power Controller Locked State:");
            pw.println("  mDisplayReadyLocked=" + mDisplayReadyLocked);
            pw.println("  mPendingRequestLocked=" + mPendingRequestLocked);
            pw.println("  mPendingRequestChangedLocked=" + mPendingRequestChangedLocked);
            pw.println("  mPendingWaitForNegativeProximityLocked="
                    + mPendingWaitForNegativeProximityLocked);
            pw.println("  mPendingUpdatePowerStateLocked=" + mPendingUpdatePowerStateLocked);
        }

        pw.println();
        pw.println("Display Power Controller Configuration:");
        pw.println("  mScreenBrightnessDozeConfig=" + mScreenBrightnessDozeConfig);
        pw.println("  mScreenBrightnessDimConfig=" + mScreenBrightnessDimConfig);
        pw.println("  mScreenBrightnessRangeMinimum=" + mScreenBrightnessRangeMinimum);
        pw.println("  mScreenBrightnessRangeMaximum=" + mScreenBrightnessRangeMaximum);
        pw.println("  mUseSoftwareAutoBrightnessConfig=" + mUseSoftwareAutoBrightnessConfig);
        pw.println("  mAllowAutoBrightnessWhileDozingConfig=" +
                mAllowAutoBrightnessWhileDozingConfig);
        pw.println("  mColorFadeFadesConfig=" + mColorFadeFadesConfig);

        mHandler.runWithScissors(new Runnable() {
            @Override
            public void run() {
                dumpLocal(pw);
            }
        }, 1000);
    }

    private void dumpLocal(PrintWriter pw) {
        pw.println();
        pw.println("Display Power Controller Thread State:");
        pw.println("  mPowerRequest=" + mPowerRequest);
        pw.println("  mWaitingForNegativeProximity=" + mWaitingForNegativeProximity);
        pw.println("  mProximitySensor=" + mProximitySensor);
        pw.println("  mProximitySensorEnabled=" + mProximitySensorEnabled);
        pw.println("  mProximityThreshold=" + mProximityThreshold);
        pw.println("  mProximity=" + proximityToString(mProximity));
        pw.println("  mPendingProximity=" + proximityToString(mPendingProximity));
        pw.println("  mPendingProximityDebounceTime="
                + TimeUtils.formatUptime(mPendingProximityDebounceTime));
        pw.println("  mScreenOffBecauseOfProximity=" + mScreenOffBecauseOfProximity);
        pw.println("  mLastBrightness=" + mLastBrightness);
        pw.println("  mLastAutoBrightnessAdjustment=" + mLastAutoBrightnessAdjustment);
        pw.println("  mAppliedAutoBrightness=" + mAppliedAutoBrightness);
        pw.println("  mAppliedDimming=" + mAppliedDimming);
        pw.println("  mAppliedLowPower=" + mAppliedLowPower);
        pw.println("  mPendingScreenOnUnblocker=" + mPendingScreenOnUnblocker);
        pw.println("  mPendingScreenOff=" + mPendingScreenOff);
        pw.println("  mReportedToPolicy=" +
                reportedToPolicyToString(mReportedScreenStateToPolicy));

        pw.println("  mScreenBrightnessRampAnimator.isAnimating()=" +
                mScreenBrightnessRampAnimator.isAnimating());

        if (mColorFadeOnAnimator != null) {
            pw.println("  mColorFadeOnAnimator.isStarted()=" +
                    mColorFadeOnAnimator.isStarted());
        }
        if (mColorFadeOffAnimator != null) {
            pw.println("  mColorFadeOffAnimator.isStarted()=" +
                    mColorFadeOffAnimator.isStarted());
        }

        if (mPowerState != null) {
            mPowerState.dump(pw);
        }

        if (mAutomaticBrightnessController != null) {
            mAutomaticBrightnessController.dump(pw);
        }

        if (mBrightnessTracker != null) {
            pw.println();
            mBrightnessTracker.dump(pw);
        }
    }

    private static String proximityToString(int state) {
        switch (state) {
            case PROXIMITY_UNKNOWN:
                return "Unknown";
            case PROXIMITY_NEGATIVE:
                return "Negative";
            case PROXIMITY_POSITIVE:
                return "Positive";
            default:
                return Integer.toString(state);
        }
    }

    private static String reportedToPolicyToString(int state) {
        switch (state) {
            case REPORTED_TO_POLICY_SCREEN_OFF:
                return "REPORTED_TO_POLICY_SCREEN_OFF";
            case REPORTED_TO_POLICY_SCREEN_TURNING_ON:
                return "REPORTED_TO_POLICY_SCREEN_TURNING_ON";
            case REPORTED_TO_POLICY_SCREEN_ON:
                return "REPORTED_TO_POLICY_SCREEN_ON";
            default:
                return Integer.toString(state);
        }
    }

    private static int clampAbsoluteBrightness(int value) {
        return MathUtils.constrain(value, PowerManager.BRIGHTNESS_OFF, PowerManager.BRIGHTNESS_ON);
    }

    private final class DisplayControllerHandler extends Handler {
        public DisplayControllerHandler(Looper looper) {
            super(looper, null, true /*async*/);
        }

        @Override
        public void handleMessage(Message msg) {
            switch (msg.what) {
                case MSG_UPDATE_POWER_STATE:
                    updatePowerState();
                    break;

                case MSG_PROXIMITY_SENSOR_DEBOUNCED:
                    debounceProximitySensor();
                    break;

                case MSG_SCREEN_ON_UNBLOCKED:
                    if (mPendingScreenOnUnblocker == msg.obj) {
                        unblockScreenOn();
                        updatePowerState();
                    }
                    break;
                case MSG_SCREEN_OFF_UNBLOCKED:
                    if (mPendingScreenOffUnblocker == msg.obj) {
                        unblockScreenOff();
                        updatePowerState();
                    }
                    break;
                case MSG_CONFIGURE_BRIGHTNESS:
                    mBrightnessConfiguration = (BrightnessConfiguration)msg.obj;
                    updatePowerState();
                    break;
            }
        }
    }

    private final SensorEventListener mProximitySensorListener = new SensorEventListener() {
        @Override
        public void onSensorChanged(SensorEvent event) {
            if (mProximitySensorEnabled) {
                final long time = SystemClock.uptimeMillis();
                final float distance = event.values[0];
                boolean positive = distance >= 0.0f && distance < mProximityThreshold;
                handleProximitySensorEvent(time, positive);
            }
        }

        @Override
        public void onAccuracyChanged(Sensor sensor, int accuracy) {
            // Not used.
        }
    };

    private final class ScreenOnUnblocker implements WindowManagerPolicy.ScreenOnListener {
        @Override
        public void onScreenOn() {
            Message msg = mHandler.obtainMessage(MSG_SCREEN_ON_UNBLOCKED, this);
            mHandler.sendMessage(msg);
        }
    }

    private final class ScreenOffUnblocker implements WindowManagerPolicy.ScreenOffListener {
        @Override
        public void onScreenOff() {
            Message msg = mHandler.obtainMessage(MSG_SCREEN_OFF_UNBLOCKED, this);
            mHandler.sendMessage(msg);
        }
    }
}