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 com.android.internal.app.IBatteryStats;
import com.android.server.LocalServices;
import com.android.server.am.BatteryStatsService;
import com.android.server.lights.LightsManager;

import android.animation.Animator;
import android.animation.ObjectAnimator;
import android.content.Context;
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.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.text.format.DateUtils;
import android.util.MathUtils;
import android.util.Slog;
import android.util.Spline;
import android.util.TimeUtils;

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

    // If true, uses the electron beam 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_ELECTRON_BEAM_ON_ANIMATION = false;


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

    private static final int ELECTRON_BEAM_ON_ANIMATION_DURATION_MILLIS = 250;
    private static final int ELECTRON_BEAM_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 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;

    // Brightness animation ramp rate in brightness units per second.
    private static final int BRIGHTNESS_RAMP_RATE_FAST = 200;
    private static final int BRIGHTNESS_RAMP_RATE_SLOW = 40;

    private final Object mLock = new Object();

    // 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 lights service.
    private final LightsManager mLights;

    // The sensor manager.
    private final SensorManager mSensorManager;

    // 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 we should fade the screen while turning it off, false if we should play
    // a stylish electron beam animation instead.
    private boolean mElectronBeamFadesConfig;

    // 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;

    // True if the screen on is being blocked.
    private boolean mScreenOnWasBlocked;

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

    // True if the screen auto-brightness value is actually being used to
    // set the display brightness.
    private boolean mUsingScreenAutoBrightness;

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

    // Animators.
    private ObjectAnimator mElectronBeamOnAnimator;
    private ObjectAnimator mElectronBeamOffAnimator;
    private RampAnimator<DisplayPowerState> mScreenBrightnessRampAnimator;

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

        mBatteryStats = BatteryStatsService.getService();
        mLights = LocalServices.getService(LightsManager.class);
        mSensorManager = sensorManager;

        final Resources resources = context.getResources();

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

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

        int screenBrightnessRangeMinimum = clampAbsoluteBrightness(Math.min(resources.getInteger(
                com.android.internal.R.integer.config_screenBrightnessSettingMinimum),
                mScreenBrightnessDimConfig));

        mScreenBrightnessRangeMaximum = PowerManager.BRIGHTNESS_ON;

        mUseSoftwareAutoBrightnessConfig = resources.getBoolean(
                com.android.internal.R.bool.config_automatic_brightness_available);
        if (mUseSoftwareAutoBrightnessConfig) {
            int[] lux = resources.getIntArray(
                    com.android.internal.R.array.config_autoBrightnessLevels);
            int[] screenBrightness = resources.getIntArray(
                    com.android.internal.R.array.config_autoBrightnessLcdBacklightValues);
            int lightSensorWarmUpTimeConfig = resources.getInteger(
                    com.android.internal.R.integer.config_lightSensorWarmupTime);

            Spline screenAutoBrightnessSpline = createAutoBrightnessSpline(lux, screenBrightness);
            if (screenAutoBrightnessSpline == null) {
                Slog.e(TAG, "Error in config.xml.  config_autoBrightnessLcdBacklightValues "
                        + "(size " + screenBrightness.length + ") "
                        + "must be monotic and have exactly one more entry than "
                        + "config_autoBrightnessLevels (size " + lux.length + ") "
                        + "which must be strictly increasing.  "
                        + "Auto-brightness will be disabled.");
                mUseSoftwareAutoBrightnessConfig = false;
            } else {
                if (screenBrightness[0] < screenBrightnessRangeMinimum) {
                    screenBrightnessRangeMinimum = clampAbsoluteBrightness(screenBrightness[0]);
                }
                mAutomaticBrightnessController = new AutomaticBrightnessController(this,
                        handler.getLooper(), sensorManager, screenAutoBrightnessSpline,
                        lightSensorWarmUpTimeConfig, screenBrightnessRangeMinimum,
                        mScreenBrightnessRangeMaximum);
            }
        }

        mScreenBrightnessRangeMinimum = screenBrightnessRangeMinimum;

        mElectronBeamFadesConfig = resources.getBoolean(
                com.android.internal.R.bool.config_animateScreenLights);

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

    }

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

    /**
     * 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 Callbacks#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);
            msg.setAsynchronous(true);
            mHandler.sendMessage(msg);
        }
    }

    private void initialize() {
        mPowerState = new DisplayPowerState(new ElectronBeam(), mCallbacks,
                mLights.getLight(LightsManager.LIGHT_ID_BACKLIGHT));

        mElectronBeamOnAnimator = ObjectAnimator.ofFloat(
                mPowerState, DisplayPowerState.ELECTRON_BEAM_LEVEL, 0.0f, 1.0f);
        mElectronBeamOnAnimator.setDuration(ELECTRON_BEAM_ON_ANIMATION_DURATION_MILLIS);
        mElectronBeamOnAnimator.addListener(mAnimatorListener);

        mElectronBeamOffAnimator = ObjectAnimator.ofFloat(
                mPowerState, DisplayPowerState.ELECTRON_BEAM_LEVEL, 1.0f, 0.0f);
        mElectronBeamOffAnimator.setDuration(ELECTRON_BEAM_OFF_ANIMATION_DURATION_MILLIS);
        mElectronBeamOffAnimator.addListener(mAnimatorListener);

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

        // Initialize screen state for battery stats.
        try {
            if (mPowerState.isScreenOn()) {
                mBatteryStats.noteScreenOn();
            } else {
                mBatteryStats.noteScreenOff();
            }
            mBatteryStats.noteScreenBrightness(mPowerState.getScreenBrightness());
        } catch (RemoteException ex) {
            // same process
        }
    }

    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 void updatePowerState() {
        // Update the power state request.
        final boolean mustNotify;
        boolean mustInitialize = false;
        boolean wasDimOrDoze = 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) {
                wasDimOrDoze = (mPowerRequest.screenState == DisplayPowerRequest.SCREEN_STATE_DIM
                        || mPowerRequest.screenState == DisplayPowerRequest.SCREEN_STATE_DOZE);
                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();
        }

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

        // Turn on the light sensor if needed.
        if (mAutomaticBrightnessController != null) {
            mAutomaticBrightnessController.updatePowerState(mPowerRequest);
        }

        // Set the screen brightness.
        if (mPowerRequest.wantScreenOnAny()) {
            int target;
            boolean slow;
            int screenAutoBrightness = mAutomaticBrightnessController != null ?
                    mAutomaticBrightnessController.getAutomaticScreenBrightness() : -1;
            if (screenAutoBrightness >= 0 && mPowerRequest.useAutoBrightness) {
                // Use current auto-brightness value.
                target = screenAutoBrightness;
                slow = mUsingScreenAutoBrightness;
                mUsingScreenAutoBrightness = true;
            } else {
                // Light sensor is disabled or not ready yet.
                // 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.
                target = mPowerRequest.screenBrightness;
                slow = false;
                mUsingScreenAutoBrightness = false;
            }
            if (mPowerRequest.screenState == DisplayPowerRequest.SCREEN_STATE_DOZE) {
                // Dim quickly to the doze state.
                target = mScreenBrightnessDozeConfig;
                slow = false;
            } else if (mPowerRequest.screenState == DisplayPowerRequest.SCREEN_STATE_DIM) {
                // Dim quickly by at least some minimum amount.
                target = Math.min(target - SCREEN_DIM_MINIMUM_REDUCTION,
                        mScreenBrightnessDimConfig);
                slow = false;
            } else if (wasDimOrDoze) {
                // Brighten quickly.
                slow = false;
            }
            animateScreenBrightness(clampScreenBrightness(target),
                    slow ? BRIGHTNESS_RAMP_RATE_SLOW : BRIGHTNESS_RAMP_RATE_FAST);
        } else {
            // Screen is off.  Don't bother changing the brightness.
            mUsingScreenAutoBrightness = false;
        }

        // Animate the screen on or off unless blocked.
        if (mScreenOffBecauseOfProximity) {
            // Screen off due to proximity.
            setScreenOn(false);
            unblockScreenOn();
        } else if (mPowerRequest.wantScreenOnAny()) {
            // Want screen on.
            // Wait for previous off animation to complete beforehand.
            // It is relatively short but if we cancel it and switch to the
            // on animation immediately then the results are pretty ugly.
            if (!mElectronBeamOffAnimator.isStarted()) {
                // Turn the screen on.  The contents of the screen may not yet
                // be visible if the electron beam has not been dismissed because
                // its last frame of animation is solid black.
                setScreenOn(true);

                if (mPowerRequest.blockScreenOn
                        && mPowerState.getElectronBeamLevel() == 0.0f) {
                    blockScreenOn();
                } else {
                    unblockScreenOn();
                    if (USE_ELECTRON_BEAM_ON_ANIMATION) {
                        if (!mElectronBeamOnAnimator.isStarted()) {
                            if (mPowerState.getElectronBeamLevel() == 1.0f) {
                                mPowerState.dismissElectronBeam();
                            } else if (mPowerState.prepareElectronBeam(
                                    mElectronBeamFadesConfig ?
                                            ElectronBeam.MODE_FADE :
                                                    ElectronBeam.MODE_WARM_UP)) {
                                mElectronBeamOnAnimator.start();
                            } else {
                                mElectronBeamOnAnimator.end();
                            }
                        }
                    } else {
                        mPowerState.setElectronBeamLevel(1.0f);
                        mPowerState.dismissElectronBeam();
                    }
                }
            }
        } else {
            // Want screen off.
            // Wait for previous on animation to complete beforehand.
            unblockScreenOn();
            if (!mElectronBeamOnAnimator.isStarted()) {
                if (!mElectronBeamOffAnimator.isStarted()) {
                    if (mPowerState.getElectronBeamLevel() == 0.0f) {
                        setScreenOn(false);
                    } else if (mPowerState.prepareElectronBeam(
                            mElectronBeamFadesConfig ?
                                    ElectronBeam.MODE_FADE :
                                            ElectronBeam.MODE_COOL_DOWN)
                            && mPowerState.isScreenOn()) {
                        mElectronBeamOffAnimator.start();
                    } else {
                        mElectronBeamOffAnimator.end();
                    }
                }
            }
        }

        // Report whether the display is ready for use.
        // We mostly care about the screen state here, ignoring brightness changes
        // which will be handled asynchronously.
        if (mustNotify
                && !mScreenOnWasBlocked
                && !mElectronBeamOnAnimator.isStarted()
                && !mElectronBeamOffAnimator.isStarted()
                && mPowerState.waitUntilClean(mCleanListener)) {
            synchronized (mLock) {
                if (!mPendingRequestChangedLocked) {
                    mDisplayReadyLocked = true;

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

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

    private void blockScreenOn() {
        if (!mScreenOnWasBlocked) {
            mScreenOnWasBlocked = true;
            if (DEBUG) {
                Slog.d(TAG, "Blocked screen on.");
                mScreenOnBlockStartRealTime = SystemClock.elapsedRealtime();
            }
        }
    }

    private void unblockScreenOn() {
        if (mScreenOnWasBlocked) {
            mScreenOnWasBlocked = false;
            long delay = SystemClock.elapsedRealtime() - mScreenOnBlockStartRealTime;
            if (delay > 1000 || DEBUG) {
                Slog.d(TAG, "Unblocked screen on after " + delay + " ms");
            }
        }
    }

    private void setScreenOn(boolean on) {
        if (mPowerState.isScreenOn() != on) {
            mPowerState.setScreenOn(on);
            try {
                if (on) {
                    mBatteryStats.noteScreenOn();
                } else {
                    mBatteryStats.noteScreenOff();
                }
            } catch (RemoteException ex) {
                // same process
            }
        }
    }

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

    private void animateScreenBrightness(int target, int rate) {
        if (mScreenBrightnessRampAnimator.animateTo(target, rate)) {
            try {
                mBatteryStats.noteScreenBrightness(target);
            } catch (RemoteException ex) {
                // same process
            }
        }
    }

    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);
                msg.setAsynchronous(true);
                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 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);

        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("  mUsingScreenAutoBrightness=" + mUsingScreenAutoBrightness);

        if (mElectronBeamOnAnimator != null) {
            pw.println("  mElectronBeamOnAnimator.isStarted()=" +
                    mElectronBeamOnAnimator.isStarted());
        }
        if (mElectronBeamOffAnimator != null) {
            pw.println("  mElectronBeamOffAnimator.isStarted()=" +
                    mElectronBeamOffAnimator.isStarted());
        }

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

        if (mAutomaticBrightnessController != null) {
            mAutomaticBrightnessController.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 Spline createAutoBrightnessSpline(int[] lux, int[] brightness) {
        try {
            final int n = brightness.length;
            float[] x = new float[n];
            float[] y = new float[n];
            y[0] = normalizeAbsoluteBrightness(brightness[0]);
            for (int i = 1; i < n; i++) {
                x[i] = lux[i - 1];
                y[i] = normalizeAbsoluteBrightness(brightness[i]);
            }

            Spline spline = Spline.createMonotoneCubicSpline(x, y);
            if (DEBUG) {
                Slog.d(TAG, "Auto-brightness spline: " + spline);
                for (float v = 1f; v < lux[lux.length - 1] * 1.25f; v *= 1.25f) {
                    Slog.d(TAG, String.format("  %7.1f: %7.1f", v, spline.interpolate(v)));
                }
            }
            return spline;
        } catch (IllegalArgumentException ex) {
            Slog.e(TAG, "Could not create auto-brightness spline.", ex);
            return null;
        }
    }

    private static float normalizeAbsoluteBrightness(int value) {
        return (float)clampAbsoluteBrightness(value) / PowerManager.BRIGHTNESS_ON;
    }

    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;
            }
        }
    }

    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.
        }
    };
}