Customize auto-brightness parameters

Auto-brightness parameters are device dependent so they should be
configurable.

The common issue with original values manifests as the screen being
perceived as too bright in dark rooms with minimum brightness and
also laginess on backlight change.

Change-Id: I2b040608bca73a3397c65c24d3b28a1514499ae6

4 files changed, 44 insertions, 23 deletions

diff --git a/core/res/res/values/config.xml b/core/res/res/values/config.xml
index c1a203842890..7aeba810b8da 100644
--- a/core/res/res/values/config.xml
+++ b/core/res/res/values/config.xml
@@ -1002,6 +1002,10 @@
     <!-- Light sensor event rate in milliseconds for automatic brightness control. -->
     <integer name="config_autoBrightnessLightSensorRate">250</integer>
 
+    <!-- The maximum range of gamma adjustment possible using the screen
+         auto-brightness adjustment setting. -->
+    <fraction name="config_autoBrightnessAdjustmentMaxGamma">300%</fraction>
+
     <!-- If we allow automatic adjustment of screen brightness while dozing, how many times we want
          to reduce it to preserve the battery. Value of 100% means no scaling. -->
     <fraction name="config_screenAutoBrightnessDozeScaleFactor">100%</fraction>
@@ -1019,6 +1023,9 @@
          adapt to the environment.  This mode may be better suited for watches. -->
     <bool name="config_autoBrightnessResetAmbientLuxAfterWarmUp">true</bool>
 
+    <!-- Period of time in which to consider light samples in milliseconds. -->
+    <integer name="config_autoBrightnessAmbientLightHorizon">10000</integer>
+
     <!-- Screen brightness used to dim the screen when the user activity
          timeout expires.  May be less than the minimum allowed brightness setting
          that can be set by the user. -->
diff --git a/core/res/res/values/symbols.xml b/core/res/res/values/symbols.xml
index 3c9327d49f2b..dffaa771ccd8 100644
--- a/core/res/res/values/symbols.xml
+++ b/core/res/res/values/symbols.xml
@@ -1689,6 +1689,8 @@
   <java-symbol type="id" name="replace_message" />
   <java-symbol type="fraction" name="config_dimBehindFadeDuration" />
   <java-symbol type="fraction" name="config_screenAutoBrightnessDozeScaleFactor" />
+  <java-symbol type="fraction" name="config_autoBrightnessAdjustmentMaxGamma" />
+  <java-symbol type="integer" name="config_autoBrightnessAmbientLightHorizon"/>
   <java-symbol type="integer" name="config_autoBrightnessBrighteningLightDebounce"/>
   <java-symbol type="integer" name="config_autoBrightnessDarkeningLightDebounce"/>
   <java-symbol type="integer" name="config_autoBrightnessLightSensorRate"/>
diff --git a/services/core/java/com/android/server/display/AutomaticBrightnessController.java b/services/core/java/com/android/server/display/AutomaticBrightnessController.java
index e15bca6ca7a1..1908f72dfd51 100644
--- a/services/core/java/com/android/server/display/AutomaticBrightnessController.java
+++ b/services/core/java/com/android/server/display/AutomaticBrightnessController.java
@@ -49,23 +49,12 @@ class AutomaticBrightnessController {
     // If true, enables the use of the screen auto-brightness adjustment setting.
     private static final boolean USE_SCREEN_AUTO_BRIGHTNESS_ADJUSTMENT = true;
 
-    // The maximum range of gamma adjustment possible using the screen
-    // auto-brightness adjustment setting.
-    private static final float SCREEN_AUTO_BRIGHTNESS_ADJUSTMENT_MAX_GAMMA = 3.0f;
-
-    // Period of time in which to consider light samples in milliseconds.
-    private static final int AMBIENT_LIGHT_HORIZON = 10000;
-
     // Hysteresis constraints for brightening or darkening.
     // The recent lux must have changed by at least this fraction relative to the
     // current ambient lux before a change will be considered.
     private static final float BRIGHTENING_LIGHT_HYSTERESIS = 0.10f;
     private static final float DARKENING_LIGHT_HYSTERESIS = 0.20f;
 
-    // The intercept used for the weighting calculation. This is used in order to keep all possible
-    // weighting values positive.
-    private static final int WEIGHTING_INTERCEPT = AMBIENT_LIGHT_HORIZON;
-
     // How long the current sensor reading is assumed to be valid beyond the current time.
     // This provides a bit of prediction, as well as ensures that the weight for the last sample is
     // non-zero, which in turn ensures that the total weight is non-zero.
@@ -132,6 +121,13 @@ class AutomaticBrightnessController {
     // and only then decide whether to change brightness.
     private final boolean mResetAmbientLuxAfterWarmUpConfig;
 
+    // Period of time in which to consider light samples in milliseconds.
+    private final int mAmbientLightHorizon;
+
+    // The intercept used for the weighting calculation. This is used in order to keep all possible
+    // weighting values positive.
+    private final int mWeightingIntercept;
+
     // Amount of time to delay auto-brightness after screen on while waiting for
     // the light sensor to warm-up in milliseconds.
     // May be 0 if no warm-up is required.
@@ -179,6 +175,10 @@ class AutomaticBrightnessController {
     // The screen auto-brightness adjustment factor in the range -1 (dimmer) to 1 (brighter)
     private float mScreenAutoBrightnessAdjustment = 0.0f;
 
+    // The maximum range of gamma adjustment possible using the screen
+    // auto-brightness adjustment setting.
+    private float mScreenAutoBrightnessAdjustmentMaxGamma;
+
     // The last screen auto-brightness gamma.  (For printing in dump() only.)
     private float mLastScreenAutoBrightnessGamma = 1.0f;
 
@@ -197,7 +197,8 @@ class AutomaticBrightnessController {
             SensorManager sensorManager, Spline autoBrightnessSpline, int lightSensorWarmUpTime,
             int brightnessMin, int brightnessMax, float dozeScaleFactor,
             int lightSensorRate, long brighteningLightDebounceConfig,
-            long darkeningLightDebounceConfig, boolean resetAmbientLuxAfterWarmUpConfig) {
+            long darkeningLightDebounceConfig, boolean resetAmbientLuxAfterWarmUpConfig,
+            int ambientLightHorizon, float autoBrightnessAdjustmentMaxGamma ) {
         mCallbacks = callbacks;
         mTwilight = LocalServices.getService(TwilightManager.class);
         mSensorManager = sensorManager;
@@ -210,9 +211,12 @@ class AutomaticBrightnessController {
         mBrighteningLightDebounceConfig = brighteningLightDebounceConfig;
         mDarkeningLightDebounceConfig = darkeningLightDebounceConfig;
         mResetAmbientLuxAfterWarmUpConfig = resetAmbientLuxAfterWarmUpConfig;
+        mAmbientLightHorizon = ambientLightHorizon;
+        mWeightingIntercept = ambientLightHorizon;
+        mScreenAutoBrightnessAdjustmentMaxGamma = autoBrightnessAdjustmentMaxGamma;
 
         mHandler = new AutomaticBrightnessHandler(looper);
-        mAmbientLightRingBuffer = new AmbientLightRingBuffer(mLightSensorRate);
+        mAmbientLightRingBuffer = new AmbientLightRingBuffer(mLightSensorRate, mAmbientLightHorizon);
 
         if (!DEBUG_PRETEND_LIGHT_SENSOR_ABSENT) {
             mLightSensor = mSensorManager.getDefaultSensor(Sensor.TYPE_LIGHT);
@@ -266,6 +270,7 @@ class AutomaticBrightnessController {
         pw.println("  mLightSensorEnabled=" + mLightSensorEnabled);
         pw.println("  mLightSensorEnableTime=" + TimeUtils.formatUptime(mLightSensorEnableTime));
         pw.println("  mAmbientLux=" + mAmbientLux);
+        pw.println("  mAmbientLightHorizon=" + mAmbientLightHorizon);
         pw.println("  mBrighteningLuxThreshold=" + mBrighteningLuxThreshold);
         pw.println("  mDarkeningLuxThreshold=" + mDarkeningLuxThreshold);
         pw.println("  mLastObservedLux=" + mLastObservedLux);
@@ -274,6 +279,7 @@ class AutomaticBrightnessController {
         pw.println("  mAmbientLightRingBuffer=" + mAmbientLightRingBuffer);
         pw.println("  mScreenAutoBrightness=" + mScreenAutoBrightness);
         pw.println("  mScreenAutoBrightnessAdjustment=" + mScreenAutoBrightnessAdjustment);
+        pw.println("  mScreenAutoBrightnessAdjustmentMaxGamma=" + mScreenAutoBrightnessAdjustmentMaxGamma);
         pw.println("  mLastScreenAutoBrightnessGamma=" + mLastScreenAutoBrightnessGamma);
         pw.println("  mDozing=" + mDozing);
     }
@@ -309,7 +315,7 @@ class AutomaticBrightnessController {
 
     private void applyLightSensorMeasurement(long time, float lux) {
         mRecentLightSamples++;
-        mAmbientLightRingBuffer.prune(time - AMBIENT_LIGHT_HORIZON);
+        mAmbientLightRingBuffer.prune(time - mAmbientLightHorizon);
         mAmbientLightRingBuffer.push(time, lux);
 
         // Remember this sample value.
@@ -360,14 +366,14 @@ class AutomaticBrightnessController {
         return sum / totalWeight;
     }
 
-    private static float calculateWeight(long startDelta, long endDelta) {
+    private float calculateWeight(long startDelta, long endDelta) {
         return weightIntegral(endDelta) - weightIntegral(startDelta);
     }
 
-    // Evaluates the integral of y = x + WEIGHTING_INTERCEPT. This is always positive for the
+    // Evaluates the integral of y = x + mWeightingIntercept. This is always positive for the
     // horizon we're looking at and provides a non-linear weighting for light samples.
-    private static float weightIntegral(long x) {
-        return x * (x * 0.5f + WEIGHTING_INTERCEPT);
+    private float weightIntegral(long x) {
+        return x * (x * 0.5f + mWeightingIntercept);
     }
 
     private long nextAmbientLightBrighteningTransition(long time) {
@@ -396,7 +402,7 @@ class AutomaticBrightnessController {
 
     private void updateAmbientLux() {
         long time = SystemClock.uptimeMillis();
-        mAmbientLightRingBuffer.prune(time - AMBIENT_LIGHT_HORIZON);
+        mAmbientLightRingBuffer.prune(time - mAmbientLightHorizon);
         updateAmbientLux(time);
     }
 
@@ -470,7 +476,7 @@ class AutomaticBrightnessController {
 
         if (USE_SCREEN_AUTO_BRIGHTNESS_ADJUSTMENT
                 && mScreenAutoBrightnessAdjustment != 0.0f) {
-            final float adjGamma = MathUtils.pow(SCREEN_AUTO_BRIGHTNESS_ADJUSTMENT_MAX_GAMMA,
+            final float adjGamma = MathUtils.pow(mScreenAutoBrightnessAdjustmentMaxGamma,
                     Math.min(1.0f, Math.max(-1.0f, -mScreenAutoBrightnessAdjustment)));
             gamma *= adjGamma;
             if (DEBUG) {
@@ -653,8 +659,8 @@ class AutomaticBrightnessController {
         private int mEnd;
         private int mCount;
 
-        public AmbientLightRingBuffer(long lightSensorRate) {
-            mCapacity = (int) Math.ceil(AMBIENT_LIGHT_HORIZON * BUFFER_SLACK / lightSensorRate);
+        public AmbientLightRingBuffer(long lightSensorRate, int ambientLightHorizon) {
+            mCapacity = (int) Math.ceil(ambientLightHorizon * BUFFER_SLACK / lightSensorRate);
             mRingLux = new float[mCapacity];
             mRingTime = new long[mCapacity];
         }
diff --git a/services/core/java/com/android/server/display/DisplayPowerController.java b/services/core/java/com/android/server/display/DisplayPowerController.java
index 7b49530e6885..433d8876dee7 100644
--- a/services/core/java/com/android/server/display/DisplayPowerController.java
+++ b/services/core/java/com/android/server/display/DisplayPowerController.java
@@ -311,6 +311,11 @@ final class DisplayPowerController implements AutomaticBrightnessController.Call
                 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);
 
         if (mUseSoftwareAutoBrightnessConfig) {
             int[] lux = resources.getIntArray(
@@ -348,7 +353,8 @@ final class DisplayPowerController implements AutomaticBrightnessController.Call
                         lightSensorWarmUpTimeConfig, screenBrightnessRangeMinimum,
                         mScreenBrightnessRangeMaximum, dozeScaleFactor, lightSensorRate,
                         brighteningLightDebounce, darkeningLightDebounce,
-                        autoBrightnessResetAmbientLuxAfterWarmUp);
+                        autoBrightnessResetAmbientLuxAfterWarmUp,
+                        ambientLightHorizon, autoBrightnessAdjustmentMaxGamma);
             }
         }