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Commit aa202a6d authored by Jeff Brown's avatar Jeff Brown
Browse files

Add a mechanism to adjust auto-brightness at night. 

Uses the twilight service to determine the hours of
sunrise and sunset.  Shortly after sunset or before sunrise
gradually start to apply a gamma correction factor to the
auto-brightness calculations to make the screen a little
dimmer at night.

The effect is relatively small and is mostly noticeable
in dark rooms.  This is just a first pass at the algorithm,
we can tweak the adjustment later to ensure that it has even less
impact in moderate or bright environments.

Change-Id: Idf89022a5d0bb52975e04779352d53fa63371178
parent 2416e096

services/java/com/android/server/SystemServer.java

+6 −1
Original line number Diff line number Diff line
@@ -741,7 +741,12 @@ class ServerThread extends Thread { 
        w.getDefaultDisplay().getMetrics(metrics);

        context.getResources().updateConfiguration(config, metrics);



        power.systemReady();

        try {

            power.systemReady(twilight);

        } catch (Throwable e) {

            reportWtf("making Power Manager Service ready", e);

        }



        try {

            pm.systemReady();

        } catch (Throwable e) {

services/java/com/android/server/power/DisplayPowerController.java

+81 −2
Original line number Diff line number Diff line
@@ -17,6 +17,8 @@ 
package com.android.server.power;



import com.android.server.LightsService;

import com.android.server.TwilightService;

import com.android.server.TwilightService.TwilightState;



import android.animation.Animator;

import android.animation.ObjectAnimator;
@@ -88,6 +90,22 @@ final class DisplayPowerController { 
    // auto-brightness adjustment setting.

    private static final float SCREEN_AUTO_BRIGHTNESS_ADJUSTMENT_MAX_GAMMA = 3.0f;



    // If true, enables the use of the current time as an auto-brightness adjustment.

    // The basic idea here is to expand the dynamic range of auto-brightness

    // when it is especially dark outside.  The light sensor tends to perform

    // poorly at low light levels so we compensate for it by making an

    // assumption about the environment.

    private static final boolean USE_TWILIGHT_ADJUSTMENT = true;



    // Specifies the maximum magnitude of the time of day adjustment.

    private static final float TWILIGHT_ADJUSTMENT_MAX_GAMMA = 1.5f;



    // The amount of time after or before sunrise over which to start adjusting

    // the gamma.  We want the change to happen gradually so that it is below the

    // threshold of perceptibility and so that the adjustment has maximum effect

    // well after dusk.

    private static final long TWILIGHT_ADJUSTMENT_TIME = DateUtils.HOUR_IN_MILLIS * 2;



    private static final int ELECTRON_BEAM_ON_ANIMATION_DURATION_MILLIS = 300;

    private static final int ELECTRON_BEAM_OFF_ANIMATION_DURATION_MILLIS = 600;
@@ -148,6 +166,9 @@ final class DisplayPowerController { 
    // The lights service.

    private final LightsService mLights;



    // The twilight service.

    private final TwilightService mTwilight;



    // The sensor manager.

    private final SensorManager mSensorManager;
@@ -291,11 +312,14 @@ final class DisplayPowerController { 
    private ObjectAnimator mElectronBeamOffAnimator;

    private RampAnimator<DisplayPowerState> mScreenBrightnessRampAnimator;



    // Twilight changed.  We might recalculate auto-brightness values.

    private boolean mTwilightChanged;



    /**

     * Creates the display power controller.

     */

    public DisplayPowerController(Looper looper, Context context, Notifier notifier,

            LightsService lights, SuspendBlocker suspendBlocker,

            LightsService lights, TwilightService twilight, SuspendBlocker suspendBlocker,

            Callbacks callbacks, Handler callbackHandler) {

        mHandler = new DisplayControllerHandler(looper);

        mNotifier = notifier;
@@ -304,6 +328,7 @@ final class DisplayPowerController { 
        mCallbackHandler = callbackHandler;



        mLights = lights;

        mTwilight = twilight;

        mSensorManager = new SystemSensorManager(mHandler.getLooper());



        final Resources resources = context.getResources();
@@ -344,6 +369,10 @@ final class DisplayPowerController { 
                && !DEBUG_PRETEND_LIGHT_SENSOR_ABSENT) {

            mLightSensor = mSensorManager.getDefaultSensor(Sensor.TYPE_LIGHT);

        }



        if (mUseSoftwareAutoBrightnessConfig && USE_TWILIGHT_ADJUSTMENT) {

            mTwilight.registerListener(mTwilightListener, mHandler);

        }

    }



    private static Spline createAutoBrightnessSpline(int[] lux, int[] brightness) {
@@ -486,7 +515,8 @@ final class DisplayPowerController { 
        // Update the power state request.

        final boolean mustNotify;

        boolean mustInitialize = false;

        boolean updateAutoBrightness = false;

        boolean updateAutoBrightness = mTwilightChanged;

        mTwilightChanged = false;



        synchronized (mLock) {

            mPendingUpdatePowerStateLocked = false;
@@ -863,6 +893,22 @@ final class DisplayPowerController { 
            }

        }



        if (USE_TWILIGHT_ADJUSTMENT) {

            TwilightState state = mTwilight.getCurrentState();

            if (state != null && state.isNight()) {

                final long now = System.currentTimeMillis();

                final float earlyGamma =

                        getTwilightGamma(now, state.getYesterdaySunset(), state.getTodaySunrise());

                final float lateGamma =

                        getTwilightGamma(now, state.getTodaySunset(), state.getTomorrowSunrise());

                gamma *= earlyGamma * lateGamma;

                if (DEBUG) {

                    Slog.d(TAG, "updateAutoBrightness: earlyGamma=" + earlyGamma

                            + ", lateGamma=" + lateGamma);

                }

            }

        }



        if (gamma != 1.0f) {

            final float in = value;

            value = FloatMath.pow(value, gamma);
@@ -889,6 +935,29 @@ final class DisplayPowerController { 
        }

    }



    private static float getTwilightGamma(long now, long lastSunset, long nextSunrise) {

        if (lastSunset < 0 || nextSunrise < 0

                || now < lastSunset || now > nextSunrise) {

            return 1.0f;

        }



        if (now < lastSunset + TWILIGHT_ADJUSTMENT_TIME) {

            return lerp(1.0f, TWILIGHT_ADJUSTMENT_MAX_GAMMA,

                    (float)(now - lastSunset) / TWILIGHT_ADJUSTMENT_TIME);

        }



        if (now > nextSunrise - TWILIGHT_ADJUSTMENT_TIME) {

            return lerp(1.0f, TWILIGHT_ADJUSTMENT_MAX_GAMMA,

                    (float)(nextSunrise - now) / TWILIGHT_ADJUSTMENT_TIME);

        }



        return TWILIGHT_ADJUSTMENT_MAX_GAMMA;

    }



    private static float lerp(float x, float y, float alpha) {

        return x + (y - x) * alpha;

    }



    private void sendOnStateChanged() {

        mCallbackHandler.post(mOnStateChangedRunnable);

    }
@@ -995,6 +1064,7 @@ final class DisplayPowerController { 
        pw.println("  mScreenAutoBrightness=" + mScreenAutoBrightness);

        pw.println("  mUsingScreenAutoBrightness=" + mUsingScreenAutoBrightness);

        pw.println("  mLastScreenAutoBrightnessGamma=" + mLastScreenAutoBrightnessGamma);

        pw.println("  mTwilight.getCurrentState()=" + mTwilight.getCurrentState());



        if (mElectronBeamOnAnimator != null) {

            pw.println("  mElectronBeamOnAnimator.isStarted()=" +
@@ -1095,4 +1165,13 @@ final class DisplayPowerController { 
            // Not used.

        }

    };



    private final TwilightService.TwilightListener mTwilightListener =

            new TwilightService.TwilightListener() {

        @Override

        public void onTwilightStateChanged() {

            mTwilightChanged = true;

            updatePowerState();

        }

    };

}

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

+3 −2
Original line number Diff line number Diff line
@@ -20,6 +20,7 @@ import com.android.internal.app.IBatteryStats; 
import com.android.server.BatteryService;

import com.android.server.EventLogTags;

import com.android.server.LightsService;

import com.android.server.TwilightService;

import com.android.server.Watchdog;

import com.android.server.am.ActivityManagerService;

import com.android.server.display.DisplayManagerService;
@@ -318,7 +319,7 @@ public final class PowerManagerService extends IPowerManager.Stub 
        }

    }



    public void systemReady() {

    public void systemReady(TwilightService twilight) {

        synchronized (mLock) {

            mSystemReady = true;
@@ -331,7 +332,7 @@ public final class PowerManagerService extends IPowerManager.Stub 
                    createSuspendBlockerLocked("PowerManagerService.Broadcasts"),

                    mPolicy, mScreenOnListener);

            mDisplayPowerController = new DisplayPowerController(mHandler.getLooper(),

                    mContext, mNotifier, mLightsService,

                    mContext, mNotifier, mLightsService, twilight,

                    createSuspendBlockerLocked("PowerManagerService.Display"),

                    mDisplayPowerControllerCallbacks, mHandler);