LowMinBrightness Mappings

- Create lowBrightness data object for ddc to use
- Read in low min brightness splines from ddc
- Call dimming method in LDA

Bug: 179428400
Test: atest DisplayServiceTests
Change-Id: If33d0164c2ca7179cb80c31f4c762e53f70b174c
diff --git a/services/core/java/com/android/server/display/AutomaticBrightnessController.java b/services/core/java/com/android/server/display/AutomaticBrightnessController.java
index 3d95fee..57b066d 100644
--- a/services/core/java/com/android/server/display/AutomaticBrightnessController.java
+++ b/services/core/java/com/android/server/display/AutomaticBrightnessController.java
@@ -53,6 +53,7 @@
 import com.android.internal.os.BackgroundThread;
 import com.android.server.EventLogTags;
 import com.android.server.display.brightness.BrightnessEvent;
+import com.android.server.display.brightness.clamper.BrightnessClamperController;
 
 import java.io.PrintWriter;
 import java.lang.annotation.Retention;
@@ -249,6 +250,7 @@
 
     // Controls Brightness range (including High Brightness Mode).
     private final BrightnessRangeController mBrightnessRangeController;
+    private final BrightnessClamperController mBrightnessClamperController;
 
     // Throttles (caps) maximum allowed brightness
     private final BrightnessThrottler mBrightnessThrottler;
@@ -284,7 +286,8 @@
             HysteresisLevels screenBrightnessThresholdsIdle, Context context,
             BrightnessRangeController brightnessModeController,
             BrightnessThrottler brightnessThrottler, int ambientLightHorizonShort,
-            int ambientLightHorizonLong, float userLux, float userNits) {
+            int ambientLightHorizonLong, float userLux, float userNits,
+            BrightnessClamperController brightnessClamperController) {
         this(new Injector(), callbacks, looper, sensorManager, lightSensor,
                 brightnessMappingStrategyMap, lightSensorWarmUpTime, brightnessMin, brightnessMax,
                 dozeScaleFactor, lightSensorRate, initialLightSensorRate,
@@ -294,7 +297,7 @@
                 screenBrightnessThresholds, ambientBrightnessThresholdsIdle,
                 screenBrightnessThresholdsIdle, context, brightnessModeController,
                 brightnessThrottler, ambientLightHorizonShort, ambientLightHorizonLong, userLux,
-                userNits
+                userNits, brightnessClamperController
         );
     }
 
@@ -310,9 +313,10 @@
             HysteresisLevels screenBrightnessThresholds,
             HysteresisLevels ambientBrightnessThresholdsIdle,
             HysteresisLevels screenBrightnessThresholdsIdle, Context context,
-            BrightnessRangeController brightnessModeController,
+            BrightnessRangeController brightnessRangeController,
             BrightnessThrottler brightnessThrottler, int ambientLightHorizonShort,
-            int ambientLightHorizonLong, float userLux, float userNits) {
+            int ambientLightHorizonLong, float userLux, float userNits,
+            BrightnessClamperController brightnessClamperController) {
         mInjector = injector;
         mClock = injector.createClock();
         mContext = context;
@@ -355,7 +359,8 @@
         mPendingForegroundAppPackageName = null;
         mForegroundAppCategory = ApplicationInfo.CATEGORY_UNDEFINED;
         mPendingForegroundAppCategory = ApplicationInfo.CATEGORY_UNDEFINED;
-        mBrightnessRangeController = brightnessModeController;
+        mBrightnessRangeController = brightnessRangeController;
+        mBrightnessClamperController = brightnessClamperController;
         mBrightnessThrottler = brightnessThrottler;
         mBrightnessMappingStrategyMap = brightnessMappingStrategyMap;
 
@@ -787,7 +792,7 @@
                     mAmbientBrightnessThresholds.getDarkeningThreshold(lux);
         }
         mBrightnessRangeController.onAmbientLuxChange(mAmbientLux);
-
+        mBrightnessClamperController.onAmbientLuxChange(mAmbientLux);
 
         // If the short term model was invalidated and the change is drastic enough, reset it.
         mShortTermModel.maybeReset(mAmbientLux);
diff --git a/services/core/java/com/android/server/display/DisplayDeviceConfig.java b/services/core/java/com/android/server/display/DisplayDeviceConfig.java
index 4116669..04e7f77 100644
--- a/services/core/java/com/android/server/display/DisplayDeviceConfig.java
+++ b/services/core/java/com/android/server/display/DisplayDeviceConfig.java
@@ -61,6 +61,7 @@
 import com.android.server.display.config.IdleScreenRefreshRateTimeoutLuxThresholdPoint;
 import com.android.server.display.config.IdleScreenRefreshRateTimeoutLuxThresholds;
 import com.android.server.display.config.IntegerArray;
+import com.android.server.display.config.LowBrightnessData;
 import com.android.server.display.config.LuxThrottling;
 import com.android.server.display.config.NitsMap;
 import com.android.server.display.config.NonNegativeFloatToFloatPoint;
@@ -555,6 +556,24 @@
  *         <majorVersion>2</majorVersion>
  *         <minorVersion>0</minorVersion>
  *     </usiVersion>
+ *     <lowBrightness enabled="true">
+ *       <transitionPoint>0.1</transitionPoint>
+ *
+ *       <nits>0.2</nits>
+ *       <nits>2.0</nits>
+ *       <nits>500.0</nits>
+ *       <nits>1000.0</nits>
+ *
+ *       <backlight>0</backlight>
+ *       <backlight>0.0001</backlight>
+ *       <backlight>0.5</backlight>
+ *       <backlight>1.0</backlight>
+ *
+ *       <brightness>0</brightness>
+ *       <brightness>0.1</brightness>
+ *       <brightness>0.5</brightness>
+ *       <brightness>1.0</brightness>
+ *     </lowBrightness>
  *     <screenBrightnessCapForWearBedtimeMode>0.1</screenBrightnessCapForWearBedtimeMode>
  *     <idleScreenRefreshRateTimeout>
  *          <luxThresholds>
@@ -568,6 +587,8 @@
  *              </point>
  *          </luxThresholds>
  *     </idleScreenRefreshRateTimeout>
+ *
+ *
  *    </displayConfiguration>
  *  }
  *  </pre>
@@ -732,6 +753,7 @@
     private Spline mBacklightToBrightnessSpline;
     private Spline mBacklightToNitsSpline;
     private Spline mNitsToBacklightSpline;
+
     private List<String> mQuirks;
     private boolean mIsHighBrightnessModeEnabled = false;
     private HighBrightnessModeData mHbmData;
@@ -872,6 +894,9 @@
     @Nullable
     private HdrBrightnessData mHdrBrightnessData;
 
+    @Nullable
+    public LowBrightnessData mLowBrightnessData;
+
     /**
      * Maximum screen brightness setting when screen brightness capped in Wear Bedtime mode.
      */
@@ -1814,6 +1839,15 @@
     }
 
     /**
+     *
+     * @return true if low brightness mode is enabled
+     */
+    @VisibleForTesting
+    public boolean getLbmEnabled() {
+        return mLowBrightnessData != null;
+    }
+
+    /**
      * @return Maximum screen brightness setting when screen brightness capped in Wear Bedtime mode.
      */
     public float getBrightnessCapForWearBedtimeMode() {
@@ -1952,6 +1986,8 @@
                 + "mUsiVersion= " + mHostUsiVersion + "\n"
                 + "mHdrBrightnessData= " + mHdrBrightnessData + "\n"
                 + "mBrightnessCapForWearBedtimeMode= " + mBrightnessCapForWearBedtimeMode
+                + "\n"
+                + (mLowBrightnessData != null ? mLowBrightnessData.toString() : "")
                 + "}";
     }
 
@@ -2002,6 +2038,9 @@
                 loadDensityMapping(config);
                 loadBrightnessDefaultFromDdcXml(config);
                 loadBrightnessConstraintsFromConfigXml();
+                if (mFlags.isEvenDimmerEnabled()) {
+                    mLowBrightnessData = LowBrightnessData.loadConfig(config);
+                }
                 loadBrightnessMap(config);
                 loadThermalThrottlingConfig(config);
                 loadPowerThrottlingConfigData(config);
@@ -2793,6 +2832,18 @@
     // These splines are used to convert from the system brightness value to the HAL backlight
     // value
     private void createBacklightConversionSplines() {
+        if (mLowBrightnessData != null) {
+            mBrightnessToBacklightSpline = mLowBrightnessData.mBrightnessToBacklight;
+            mBacklightToBrightnessSpline = mLowBrightnessData.mBacklightToBrightness;
+            mBacklightToNitsSpline = mLowBrightnessData.mBacklightToNits;
+            mNitsToBacklightSpline = mLowBrightnessData.mNitsToBacklight;
+
+            mNits = mLowBrightnessData.mNits;
+            mBrightness = mLowBrightnessData.mBrightness;
+            mBacklight = mLowBrightnessData.mBacklight;
+            return;
+        }
+
         mBrightness = new float[mBacklight.length];
         for (int i = 0; i < mBrightness.length; i++) {
             mBrightness[i] = MathUtils.map(mBacklight[0],
diff --git a/services/core/java/com/android/server/display/DisplayPowerController.java b/services/core/java/com/android/server/display/DisplayPowerController.java
index 77a43d0..67f2814 100644
--- a/services/core/java/com/android/server/display/DisplayPowerController.java
+++ b/services/core/java/com/android/server/display/DisplayPowerController.java
@@ -1165,7 +1165,8 @@
                     screenBrightnessThresholds, ambientBrightnessThresholdsIdle,
                     screenBrightnessThresholdsIdle, mContext, mBrightnessRangeController,
                     mBrightnessThrottler, mDisplayDeviceConfig.getAmbientHorizonShort(),
-                    mDisplayDeviceConfig.getAmbientHorizonLong(), userLux, userNits);
+                    mDisplayDeviceConfig.getAmbientHorizonLong(), userLux, userNits,
+                    mBrightnessClamperController);
             mDisplayBrightnessController.setAutomaticBrightnessController(
                     mAutomaticBrightnessController);
 
@@ -2479,6 +2480,7 @@
     public void setBrightnessToFollow(float leadDisplayBrightness, float nits, float ambientLux,
             boolean slowChange) {
         mBrightnessRangeController.onAmbientLuxChange(ambientLux);
+        mBrightnessClamperController.onAmbientLuxChange(ambientLux);
         if (nits == BrightnessMappingStrategy.INVALID_NITS) {
             mDisplayBrightnessController.setBrightnessToFollow(leadDisplayBrightness, slowChange);
         } else {
@@ -3176,7 +3178,9 @@
                 HysteresisLevels screenBrightnessThresholdsIdle, Context context,
                 BrightnessRangeController brightnessModeController,
                 BrightnessThrottler brightnessThrottler, int ambientLightHorizonShort,
-                int ambientLightHorizonLong, float userLux, float userNits) {
+                int ambientLightHorizonLong, float userLux, float userNits,
+                BrightnessClamperController brightnessClamperController) {
+
             return new AutomaticBrightnessController(callbacks, looper, sensorManager, lightSensor,
                     brightnessMappingStrategyMap, lightSensorWarmUpTime, brightnessMin,
                     brightnessMax, dozeScaleFactor, lightSensorRate, initialLightSensorRate,
@@ -3186,7 +3190,7 @@
                     screenBrightnessThresholds, ambientBrightnessThresholdsIdle,
                     screenBrightnessThresholdsIdle, context, brightnessModeController,
                     brightnessThrottler, ambientLightHorizonShort, ambientLightHorizonLong, userLux,
-                    userNits);
+                    userNits, brightnessClamperController);
         }
 
         BrightnessMappingStrategy getDefaultModeBrightnessMapper(Context context,
diff --git a/services/core/java/com/android/server/display/LocalDisplayAdapter.java b/services/core/java/com/android/server/display/LocalDisplayAdapter.java
index b2fd9ed..3b3a03b 100644
--- a/services/core/java/com/android/server/display/LocalDisplayAdapter.java
+++ b/services/core/java/com/android/server/display/LocalDisplayAdapter.java
@@ -37,6 +37,7 @@
 import android.os.Trace;
 import android.util.DisplayUtils;
 import android.util.LongSparseArray;
+import android.util.MathUtils;
 import android.util.Slog;
 import android.util.SparseArray;
 import android.view.Display;
@@ -78,6 +79,13 @@
     private static final String UNIQUE_ID_PREFIX = "local:";
 
     private static final String PROPERTY_EMULATOR_CIRCULAR = "ro.boot.emulator.circular";
+    // Min and max strengths for even dimmer feature.
+    private static final float EVEN_DIMMER_MIN_STRENGTH = 0.0f;
+    private static final float EVEN_DIMMER_MAX_STRENGTH = 70.0f; // not too dim yet.
+    private static final float BRIGHTNESS_MIN = 0.0f;
+    // The brightness at which we start using color matrices rather than backlight,
+    // to dim the display
+    private static final float BACKLIGHT_COLOR_TRANSITION_POINT = 0.1f;
 
     private final LongSparseArray<LocalDisplayDevice> mDevices = new LongSparseArray<>();
 
@@ -91,6 +99,8 @@
 
     private Context mOverlayContext;
 
+    private int mEvenDimmerStrength = -1;
+
     // Called with SyncRoot lock held.
     LocalDisplayAdapter(DisplayManagerService.SyncRoot syncRoot, Context context,
             Handler handler, Listener listener, DisplayManagerFlags flags,
@@ -928,6 +938,10 @@
                             final float nits = backlightToNits(backlight);
                             final float sdrNits = backlightToNits(sdrBacklight);
 
+                            if (getFeatureFlags().isEvenDimmerEnabled()) {
+                                applyColorMatrixBasedDimming(brightnessState);
+                            }
+
                             mBacklightAdapter.setBacklight(sdrBacklight, sdrNits, backlight, nits);
                             Trace.traceCounter(Trace.TRACE_TAG_POWER,
                                     "ScreenBrightness",
@@ -974,6 +988,22 @@
                             }
                         }
                     }
+
+                    private void applyColorMatrixBasedDimming(float brightnessState) {
+                        int strength = (int) (MathUtils.constrainedMap(
+                                EVEN_DIMMER_MAX_STRENGTH, EVEN_DIMMER_MIN_STRENGTH, // to this range
+                                BRIGHTNESS_MIN, BACKLIGHT_COLOR_TRANSITION_POINT, // from this range
+                                brightnessState) + 0.5); // map this (+ rounded up)
+
+                        if (mEvenDimmerStrength < 0 // uninitialised
+                                || MathUtils.abs(mEvenDimmerStrength - strength) > 1
+                                || strength <= 1) {
+                            mEvenDimmerStrength = strength;
+                        }
+
+                        // TODO: use `enabled` and `mRbcStrength` to set color matrices here
+                        // TODO: boolean enabled = mEvenDimmerStrength > 0.0f;
+                    }
                 };
             }
             return null;
diff --git a/services/core/java/com/android/server/display/brightness/clamper/BrightnessClamperController.java b/services/core/java/com/android/server/display/brightness/clamper/BrightnessClamperController.java
index 18e8fab..d8a4500 100644
--- a/services/core/java/com/android/server/display/brightness/clamper/BrightnessClamperController.java
+++ b/services/core/java/com/android/server/display/brightness/clamper/BrightnessClamperController.java
@@ -189,6 +189,13 @@
         mModifiers.forEach(BrightnessStateModifier::stop);
     }
 
+    /**
+     * Notifies modifiers that ambient lux has changed.
+     * @param ambientLux current lux, debounced
+     */
+    public void onAmbientLuxChange(float ambientLux) {
+        mModifiers.forEach(modifier -> modifier.onAmbientLuxChange(ambientLux));
+    }
 
     // Called in DisplayControllerHandler
     private void recalculateBrightnessCap() {
diff --git a/services/core/java/com/android/server/display/brightness/clamper/BrightnessLowLuxModifier.java b/services/core/java/com/android/server/display/brightness/clamper/BrightnessLowLuxModifier.java
index 7f1f7a9..a91bb59 100644
--- a/services/core/java/com/android/server/display/brightness/clamper/BrightnessLowLuxModifier.java
+++ b/services/core/java/com/android/server/display/brightness/clamper/BrightnessLowLuxModifier.java
@@ -39,21 +39,21 @@
  * Class used to prevent the screen brightness dipping below a certain value, based on current
  * lux conditions and user preferred minimum.
  */
-public class BrightnessLowLuxModifier implements
-        BrightnessStateModifier {
+public class BrightnessLowLuxModifier extends BrightnessModifier {
 
     // To enable these logs, run:
     // 'adb shell setprop persist.log.tag.BrightnessLowLuxModifier DEBUG && adb reboot'
     private static final String TAG = "BrightnessLowLuxModifier";
     private static final boolean DEBUG = DebugUtils.isDebuggable(TAG);
+    private static final float MIN_NITS = 2.0f;
     private final SettingsObserver mSettingsObserver;
     private final ContentResolver mContentResolver;
     private final Handler mHandler;
     private final BrightnessClamperController.ClamperChangeListener mChangeListener;
-    protected float mSettingNitsLowerBound = PowerManager.BRIGHTNESS_MIN;
     private int mReason;
     private float mBrightnessLowerBound;
     private boolean mIsActive;
+    private float mAmbientLux;
 
     @VisibleForTesting
     BrightnessLowLuxModifier(Handler handler,
@@ -78,17 +78,17 @@
         int userId = UserHandle.USER_CURRENT;
         float settingNitsLowerBound = Settings.Secure.getFloatForUser(
                 mContentResolver, Settings.Secure.EVEN_DIMMER_MIN_NITS,
-                /* def= */ PowerManager.BRIGHTNESS_MIN, userId);
+                /* def= */ MIN_NITS, userId);
 
-        boolean isActive = Settings.Secure.getIntForUser(mContentResolver,
+        boolean isActive = Settings.Secure.getFloatForUser(mContentResolver,
                 Settings.Secure.EVEN_DIMMER_ACTIVATED,
-                /* def= */ 0, userId) == 1;
+                /* def= */ 0, userId) == 1.0f;
 
-        // TODO: luxBasedNitsLowerBound = mMinNitsToLuxSpline(currentLux);
-        float luxBasedNitsLowerBound = 0.0f;
+        // TODO: luxBasedNitsLowerBound = mMinLuxToNitsSpline(currentLux);
+        float luxBasedNitsLowerBound = 2.0f;
 
-        // TODO: final float nitsLowerBound = isActive ? Math.max(settingNitsLowerBound,
-                // luxBasedNitsLowerBound) : PowerManager.BRIGHTNESS_MIN;
+        final float nitsLowerBound = isActive ? Math.max(settingNitsLowerBound,
+                 luxBasedNitsLowerBound) : MIN_NITS;
 
         final int reason = settingNitsLowerBound > luxBasedNitsLowerBound
                 ? BrightnessReason.MODIFIER_MIN_USER_SET_LOWER_BOUND
@@ -104,8 +104,13 @@
             mReason = reason;
             if (DEBUG) {
                 Slog.i(TAG, "isActive: " + isActive
-                        + ", settingNitsLowerBound: " + settingNitsLowerBound
-                        + ", lowerBound: " + brightnessLowerBound);
+                        + ", brightnessLowerBound: " + brightnessLowerBound
+                        + ", mAmbientLux: " + mAmbientLux
+                        + ", mReason: " + (
+                        mReason == BrightnessReason.MODIFIER_MIN_USER_SET_LOWER_BOUND ? "minSetting"
+                                : "lux")
+                        + ", nitsLowerBound: " + nitsLowerBound
+                );
             }
             mBrightnessLowerBound = brightnessLowerBound;
             mChangeListener.onChanged();
@@ -132,6 +137,22 @@
     }
 
     @Override
+    boolean shouldApply(DisplayManagerInternal.DisplayPowerRequest request) {
+        return mIsActive;
+    }
+
+    @Override
+    float getBrightnessAdjusted(float currentBrightness,
+            DisplayManagerInternal.DisplayPowerRequest request) {
+        return Math.max(mBrightnessLowerBound, currentBrightness);
+    }
+
+    @Override
+    int getModifier() {
+        return mReason;
+    }
+
+    @Override
     public void apply(DisplayManagerInternal.DisplayPowerRequest request,
             DisplayBrightnessState.Builder stateBuilder) {
         stateBuilder.setMinBrightness(mBrightnessLowerBound);
@@ -150,10 +171,16 @@
     }
 
     @Override
+    public void onAmbientLuxChange(float ambientLux) {
+        mAmbientLux = ambientLux;
+        recalculateLowerBound();
+    }
+
+    @Override
     public void dump(PrintWriter pw) {
         pw.println("BrightnessLowLuxModifier:");
-        pw.println("  mBrightnessLowerBound=" + mBrightnessLowerBound);
         pw.println("  mIsActive=" + mIsActive);
+        pw.println("  mBrightnessLowerBound=" + mBrightnessLowerBound);
         pw.println("  mReason=" + mReason);
     }
 
diff --git a/services/core/java/com/android/server/display/brightness/clamper/BrightnessModifier.java b/services/core/java/com/android/server/display/brightness/clamper/BrightnessModifier.java
index be8fa5a..2a3dd87 100644
--- a/services/core/java/com/android/server/display/brightness/clamper/BrightnessModifier.java
+++ b/services/core/java/com/android/server/display/brightness/clamper/BrightnessModifier.java
@@ -68,4 +68,9 @@
     public void stop() {
         // do nothing
     }
+
+    @Override
+    public void onAmbientLuxChange(float ambientLux) {
+        // do nothing
+    }
 }
diff --git a/services/core/java/com/android/server/display/brightness/clamper/BrightnessStateModifier.java b/services/core/java/com/android/server/display/brightness/clamper/BrightnessStateModifier.java
index 441ba8f..2234258 100644
--- a/services/core/java/com/android/server/display/brightness/clamper/BrightnessStateModifier.java
+++ b/services/core/java/com/android/server/display/brightness/clamper/BrightnessStateModifier.java
@@ -42,4 +42,10 @@
      * Called when stopped. Listeners can be unregistered here.
      */
     void stop();
+
+    /**
+     * Allows modifiers to react to ambient lux changes.
+     * @param ambientLux current debounced lux.
+     */
+    void onAmbientLuxChange(float ambientLux);
 }
diff --git a/services/core/java/com/android/server/display/config/LowBrightnessData.java b/services/core/java/com/android/server/display/config/LowBrightnessData.java
new file mode 100644
index 0000000..aa82533
--- /dev/null
+++ b/services/core/java/com/android/server/display/config/LowBrightnessData.java
@@ -0,0 +1,142 @@
+/*
+ * Copyright (C) 2023 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.config;
+
+import android.annotation.Nullable;
+import android.util.Slog;
+import android.util.Spline;
+
+import com.android.internal.annotations.VisibleForTesting;
+
+import java.util.Arrays;
+import java.util.List;
+
+/**
+ * Brightness config for low brightness mode
+ */
+public class LowBrightnessData {
+    private static final String TAG = "LowBrightnessData";
+
+    /**
+     * Brightness value at which lower brightness methods are used.
+     */
+    public final float mTransitionPoint;
+
+    /**
+     * Nits array, maps to mBacklight
+     */
+    public final float[] mNits;
+
+    /**
+     * Backlight array, maps to mBrightness and mNits
+     */
+    public final float[] mBacklight;
+
+    /**
+     * Brightness array, maps to mBacklight
+     */
+    public final float[] mBrightness;
+    /**
+     * Spline, mapping between backlight and nits
+     */
+    public final Spline mBacklightToNits;
+    /**
+     * Spline, mapping between nits and backlight
+     */
+    public final Spline mNitsToBacklight;
+    /**
+     * Spline, mapping between brightness and backlight
+     */
+    public final Spline mBrightnessToBacklight;
+    /**
+     * Spline, mapping between backlight and brightness
+     */
+    public final Spline mBacklightToBrightness;
+
+    @VisibleForTesting
+    public LowBrightnessData(float transitionPoint, float[] nits,
+            float[] backlight, float[] brightness, Spline backlightToNits,
+            Spline nitsToBacklight, Spline brightnessToBacklight, Spline backlightToBrightness) {
+        mTransitionPoint = transitionPoint;
+        mNits = nits;
+        mBacklight = backlight;
+        mBrightness = brightness;
+        mBacklightToNits = backlightToNits;
+        mNitsToBacklight = nitsToBacklight;
+        mBrightnessToBacklight = brightnessToBacklight;
+        mBacklightToBrightness = backlightToBrightness;
+    }
+
+    @Override
+    public String toString() {
+        return "LowBrightnessData {"
+                + "mTransitionPoint: " + mTransitionPoint
+                + ", mNits: " + Arrays.toString(mNits)
+                + ", mBacklight: " + Arrays.toString(mBacklight)
+                + ", mBrightness: " + Arrays.toString(mBrightness)
+                + ", mBacklightToNits: " + mBacklightToNits
+                + ", mNitsToBacklight: " + mNitsToBacklight
+                + ", mBrightnessToBacklight: " + mBrightnessToBacklight
+                + ", mBacklightToBrightness: " + mBacklightToBrightness
+                + "} ";
+    }
+
+    /**
+     * Loads LowBrightnessData from DisplayConfiguration
+     */
+    @Nullable
+    public static LowBrightnessData loadConfig(DisplayConfiguration config) {
+        final LowBrightnessMode lbm = config.getLowBrightness();
+        if (lbm == null) {
+            return null;
+        }
+
+        boolean lbmIsEnabled = lbm.getEnabled();
+        if (!lbmIsEnabled) {
+            return null;
+        }
+
+        List<Float> nitsList = lbm.getNits();
+        List<Float> backlightList = lbm.getBacklight();
+        List<Float> brightnessList = lbm.getBrightness();
+        float transitionPoints = lbm.getTransitionPoint().floatValue();
+
+        if (nitsList.isEmpty()
+                || backlightList.size() != brightnessList.size()
+                || backlightList.size() != nitsList.size()) {
+            Slog.e(TAG, "Invalid low brightness array lengths");
+            return null;
+        }
+
+        float[] nits = new float[nitsList.size()];
+        float[] backlight = new float[nitsList.size()];
+        float[] brightness = new float[nitsList.size()];
+
+        for (int i = 0; i < nitsList.size(); i++) {
+            nits[i] = nitsList.get(i);
+            backlight[i] = backlightList.get(i);
+            brightness[i] = brightnessList.get(i);
+        }
+
+        return new LowBrightnessData(transitionPoints, nits, backlight, brightness,
+                Spline.createSpline(backlight, nits),
+                Spline.createSpline(nits, backlight),
+                Spline.createSpline(brightness, backlight),
+                Spline.createSpline(backlight, brightness)
+                );
+    }
+}
diff --git a/services/core/xsd/display-device-config/display-device-config.xsd b/services/core/xsd/display-device-config/display-device-config.xsd
index d0df2b2..1f54518 100644
--- a/services/core/xsd/display-device-config/display-device-config.xsd
+++ b/services/core/xsd/display-device-config/display-device-config.xsd
@@ -162,6 +162,10 @@
                 <xs:element type="usiVersion" name="usiVersion">
                     <xs:annotation name="final"/>
                 </xs:element>
+                <xs:element type="lowBrightnessMode" name="lowBrightness">
+                    <xs:attribute name="enabled" type="xs:boolean" use="optional"/>
+                    <xs:annotation name="final"/>
+                </xs:element>
                 <!-- Maximum screen brightness setting when screen brightness capped in
                 Wear Bedtime mode. This must be a non-negative decimal within the range defined by
                 the first and the last brightness value in screenBrightnessMap. -->
@@ -172,6 +176,7 @@
                 <xs:element type="idleScreenRefreshRateTimeout" name="idleScreenRefreshRateTimeout" minOccurs="0">
                     <xs:annotation name="final"/>
                 </xs:element>
+
             </xs:sequence>
         </xs:complexType>
     </xs:element>
@@ -216,6 +221,21 @@
         </xs:restriction>
     </xs:simpleType>
 
+    <xs:complexType name="lowBrightnessMode">
+        <xs:sequence>
+            <xs:element name="transitionPoint" type="nonNegativeDecimal" minOccurs="1"
+                maxOccurs="1">
+            </xs:element>
+            <xs:element name="nits" type="xs:float" maxOccurs="unbounded">
+            </xs:element>
+            <xs:element name="backlight" type="xs:float" maxOccurs="unbounded">
+            </xs:element>
+            <xs:element name="brightness" type="xs:float" maxOccurs="unbounded">
+            </xs:element>
+        </xs:sequence>
+        <xs:attribute name="enabled" type="xs:boolean" use="optional"/>
+    </xs:complexType>
+
     <xs:complexType name="highBrightnessMode">
         <xs:all>
             <xs:element name="transitionPoint" type="nonNegativeDecimal" minOccurs="1"
diff --git a/services/core/xsd/display-device-config/schema/current.txt b/services/core/xsd/display-device-config/schema/current.txt
index 00dc908..c39c3d7 100644
--- a/services/core/xsd/display-device-config/schema/current.txt
+++ b/services/core/xsd/display-device-config/schema/current.txt
@@ -113,6 +113,7 @@
     method public com.android.server.display.config.HighBrightnessMode getHighBrightnessMode();
     method public final com.android.server.display.config.IdleScreenRefreshRateTimeout getIdleScreenRefreshRateTimeout();
     method public final com.android.server.display.config.SensorDetails getLightSensor();
+    method public final com.android.server.display.config.LowBrightnessMode getLowBrightness();
     method public com.android.server.display.config.LuxThrottling getLuxThrottling();
     method @Nullable public final String getName();
     method public com.android.server.display.config.PowerThrottlingConfig getPowerThrottlingConfig();
@@ -149,6 +150,7 @@
     method public void setHighBrightnessMode(com.android.server.display.config.HighBrightnessMode);
     method public final void setIdleScreenRefreshRateTimeout(com.android.server.display.config.IdleScreenRefreshRateTimeout);
     method public final void setLightSensor(com.android.server.display.config.SensorDetails);
+    method public final void setLowBrightness(com.android.server.display.config.LowBrightnessMode);
     method public void setLuxThrottling(com.android.server.display.config.LuxThrottling);
     method public final void setName(@Nullable String);
     method public void setPowerThrottlingConfig(com.android.server.display.config.PowerThrottlingConfig);
@@ -248,6 +250,17 @@
     method public java.util.List<java.math.BigInteger> getItem();
   }
 
+  public class LowBrightnessMode {
+    ctor public LowBrightnessMode();
+    method public java.util.List<java.lang.Float> getBacklight();
+    method public java.util.List<java.lang.Float> getBrightness();
+    method public boolean getEnabled();
+    method public java.util.List<java.lang.Float> getNits();
+    method public java.math.BigDecimal getTransitionPoint();
+    method public void setEnabled(boolean);
+    method public void setTransitionPoint(java.math.BigDecimal);
+  }
+
   public class LuxThrottling {
     ctor public LuxThrottling();
     method @NonNull public final java.util.List<com.android.server.display.config.BrightnessLimitMap> getBrightnessLimitMap();
diff --git a/services/tests/displayservicetests/src/com/android/server/display/AutomaticBrightnessControllerTest.java b/services/tests/displayservicetests/src/com/android/server/display/AutomaticBrightnessControllerTest.java
index 705dac5..347c53a 100644
--- a/services/tests/displayservicetests/src/com/android/server/display/AutomaticBrightnessControllerTest.java
+++ b/services/tests/displayservicetests/src/com/android/server/display/AutomaticBrightnessControllerTest.java
@@ -51,6 +51,7 @@
 import androidx.test.filters.SmallTest;
 import androidx.test.runner.AndroidJUnit4;
 
+import com.android.server.display.brightness.clamper.BrightnessClamperController;
 import com.android.server.testutils.OffsettableClock;
 
 import org.junit.After;
@@ -95,6 +96,8 @@
     @Mock HysteresisLevels mScreenBrightnessThresholdsIdle;
     @Mock Handler mNoOpHandler;
     @Mock BrightnessRangeController mBrightnessRangeController;
+    @Mock
+    BrightnessClamperController mBrightnessClamperController;
     @Mock BrightnessThrottler mBrightnessThrottler;
 
     @Before
@@ -160,7 +163,8 @@
                 mAmbientBrightnessThresholdsIdle, mScreenBrightnessThresholdsIdle,
                 mContext, mBrightnessRangeController, mBrightnessThrottler,
                 useHorizon ? AMBIENT_LIGHT_HORIZON_SHORT : 1,
-                useHorizon ? AMBIENT_LIGHT_HORIZON_LONG : 10000, userLux, userNits
+                useHorizon ? AMBIENT_LIGHT_HORIZON_LONG : 10000, userLux, userNits,
+                mBrightnessClamperController
         );
 
         when(mBrightnessRangeController.getCurrentBrightnessMax()).thenReturn(
diff --git a/services/tests/displayservicetests/src/com/android/server/display/DisplayDeviceConfigTest.java b/services/tests/displayservicetests/src/com/android/server/display/DisplayDeviceConfigTest.java
index 35b69f8..73a2f65 100644
--- a/services/tests/displayservicetests/src/com/android/server/display/DisplayDeviceConfigTest.java
+++ b/services/tests/displayservicetests/src/com/android/server/display/DisplayDeviceConfigTest.java
@@ -44,6 +44,7 @@
 import android.hardware.display.DisplayManagerInternal;
 import android.os.PowerManager;
 import android.os.Temperature;
+import android.platform.test.annotations.RequiresFlagsEnabled;
 import android.provider.Settings;
 import android.util.SparseArray;
 import android.util.Spline;
@@ -57,6 +58,7 @@
 import com.android.server.display.config.IdleScreenRefreshRateTimeoutLuxThresholdPoint;
 import com.android.server.display.config.ThermalStatus;
 import com.android.server.display.feature.DisplayManagerFlags;
+import com.android.server.display.feature.flags.Flags;
 
 import org.junit.Before;
 import org.junit.Test;
@@ -380,7 +382,7 @@
     public void testInvalidLuxThrottling() throws Exception {
         setupDisplayDeviceConfigFromDisplayConfigFile(
                 getContent(getInvalidLuxThrottling(), getValidProxSensor(),
-                        /* includeIdleMode= */ true));
+                        /* includeIdleMode= */ true, /* enableEvenDimmer */ false));
 
         Map<DisplayDeviceConfig.BrightnessLimitMapType, Map<Float, Float>> luxThrottlingData =
                 mDisplayDeviceConfig.getLuxThrottlingData();
@@ -588,7 +590,7 @@
     public void testProximitySensorWithEmptyValuesFromDisplayConfig() throws IOException {
         setupDisplayDeviceConfigFromDisplayConfigFile(
                 getContent(getValidLuxThrottling(), getProxSensorWithEmptyValues(),
-                        /* includeIdleMode= */ true));
+                        /* includeIdleMode= */ true, /* enableEvenDimmer */ false));
         assertNull(mDisplayDeviceConfig.getProximitySensor());
     }
 
@@ -596,7 +598,7 @@
     public void testProximitySensorWithRefreshRatesFromDisplayConfig() throws IOException {
         setupDisplayDeviceConfigFromDisplayConfigFile(
                 getContent(getValidLuxThrottling(), getValidProxSensorWithRefreshRateAndVsyncRate(),
-                        /* includeIdleMode= */ true));
+                        /* includeIdleMode= */ true, /* enableEvenDimmer */ false));
         assertEquals("test_proximity_sensor",
                 mDisplayDeviceConfig.getProximitySensor().type);
         assertEquals("Test Proximity Sensor",
@@ -784,7 +786,7 @@
     @Test
     public void testBrightnessRamps_IdleFallsBackToConfigInteractive() throws IOException {
         setupDisplayDeviceConfigFromDisplayConfigFile(getContent(getValidLuxThrottling(),
-                getValidProxSensor(), /* includeIdleMode= */ false));
+                getValidProxSensor(), /* includeIdleMode= */ false, /* enableEvenDimmer */ false));
 
         assertEquals(mDisplayDeviceConfig.getBrightnessRampDecreaseMaxMillis(), 3000);
         assertEquals(mDisplayDeviceConfig.getBrightnessRampIncreaseMaxMillis(), 2000);
@@ -801,14 +803,14 @@
     @Test
     public void testBrightnessCapForWearBedtimeMode() throws IOException {
         setupDisplayDeviceConfigFromDisplayConfigFile(getContent(getValidLuxThrottling(),
-                getValidProxSensor(), /* includeIdleMode= */ false));
+                getValidProxSensor(), /* includeIdleMode= */ false, /* enableEvenDimmer */ false));
         assertEquals(0.1f, mDisplayDeviceConfig.getBrightnessCapForWearBedtimeMode(), ZERO_DELTA);
     }
 
     @Test
     public void testAutoBrightnessBrighteningLevels() throws IOException {
         setupDisplayDeviceConfigFromDisplayConfigFile(getContent(getValidLuxThrottling(),
-                getValidProxSensor(), /* includeIdleMode= */ false));
+                getValidProxSensor(), /* includeIdleMode= */ false, /* enableEvenDimmer */ false));
 
         assertArrayEquals(new float[]{0.0f, 80},
                 mDisplayDeviceConfig.getAutoBrightnessBrighteningLevelsLux(
@@ -871,7 +873,7 @@
         when(mFlags.areAutoBrightnessModesEnabled()).thenReturn(false);
         setupDisplayDeviceConfigFromConfigResourceFile();
         setupDisplayDeviceConfigFromDisplayConfigFile(getContent(getValidLuxThrottling(),
-                getValidProxSensor(), /* includeIdleMode= */ false));
+                getValidProxSensor(), /* includeIdleMode= */ false, /* enableEvenDimmer */ false));
 
         assertArrayEquals(new float[]{brightnessIntToFloat(50), brightnessIntToFloat(100),
                         brightnessIntToFloat(150)},
@@ -904,6 +906,18 @@
         assertFalse(mDisplayDeviceConfig.isAutoBrightnessAvailable());
     }
 
+    @RequiresFlagsEnabled(Flags.FLAG_EVEN_DIMMER)
+    @Test
+    public void testEvenDimmer() throws IOException {
+        when(mFlags.isEvenDimmerEnabled()).thenReturn(true);
+        setupDisplayDeviceConfigFromDisplayConfigFile(getContent(getValidLuxThrottling(),
+                getValidProxSensor(), /* includeIdleMode= */ false, /* enableEvenDimmer */ true));
+
+        assertTrue(mDisplayDeviceConfig.getLbmEnabled());
+        assertEquals(0.0001f, mDisplayDeviceConfig.getBacklightFromBrightness(0.1f), ZERO_DELTA);
+        assertEquals(0.2f, mDisplayDeviceConfig.getNitsFromBacklight(0.0f), ZERO_DELTA);
+    }
+
     private String getValidLuxThrottling() {
         return "<luxThrottling>\n"
                 + "    <brightnessLimitMap>\n"
@@ -1229,11 +1243,11 @@
 
     private String getContent() {
         return getContent(getValidLuxThrottling(), getValidProxSensor(),
-                /* includeIdleMode= */ true);
+                /* includeIdleMode= */ true, false);
     }
 
     private String getContent(String brightnessCapConfig, String proxSensor,
-            boolean includeIdleMode) {
+            boolean includeIdleMode, boolean enableEvenDimmer) {
         return "<?xml version='1.0' encoding='utf-8' standalone='yes' ?>\n"
                 + "<displayConfiguration>\n"
                 +   "<name>Example Display</name>\n"
@@ -1603,6 +1617,7 @@
                 +       "<majorVersion>2</majorVersion>\n"
                 +       "<minorVersion>0</minorVersion>\n"
                 +   "</usiVersion>\n"
+                + evenDimmerConfig(enableEvenDimmer)
                 +   "<screenBrightnessCapForWearBedtimeMode>"
                 +       "0.1"
                 +   "</screenBrightnessCapForWearBedtimeMode>"
@@ -1621,6 +1636,24 @@
                 + "</displayConfiguration>\n";
     }
 
+    private String evenDimmerConfig(boolean enabled) {
+        return (enabled ? "<lowBrightness enabled=\"true\">" : "<lowBrightness enabled=\"false\">")
+                + "  <transitionPoint>0.1</transitionPoint>\n"
+                + "  <nits>0.2</nits>\n"
+                + "  <nits>2.0</nits>\n"
+                + "  <nits>500.0</nits>\n"
+                + "  <nits>1000.0</nits>\n"
+                + "  <backlight>0</backlight>\n"
+                + "  <backlight>0.0001</backlight>\n"
+                + "  <backlight>0.5</backlight>\n"
+                + "  <backlight>1.0</backlight>\n"
+                + "  <brightness>0</brightness>\n"
+                + "  <brightness>0.1</brightness>\n"
+                + "  <brightness>0.5</brightness>\n"
+                + "  <brightness>1.0</brightness>\n"
+                + "</lowBrightness>";
+    }
+
     private void mockDeviceConfigs() {
         when(mResources.getFloat(com.android.internal.R.dimen
                 .config_screenBrightnessSettingDefaultFloat)).thenReturn(0.5f);
diff --git a/services/tests/displayservicetests/src/com/android/server/display/DisplayPowerControllerTest.java b/services/tests/displayservicetests/src/com/android/server/display/DisplayPowerControllerTest.java
index fb23213..19674c2 100644
--- a/services/tests/displayservicetests/src/com/android/server/display/DisplayPowerControllerTest.java
+++ b/services/tests/displayservicetests/src/com/android/server/display/DisplayPowerControllerTest.java
@@ -1184,7 +1184,8 @@
                 /* ambientLightHorizonShort= */ anyInt(),
                 /* ambientLightHorizonLong= */ anyInt(),
                 eq(lux),
-                eq(nits)
+                eq(nits),
+                any(BrightnessClamperController.class)
         );
     }
 
@@ -2119,7 +2120,8 @@
                 HysteresisLevels screenBrightnessThresholdsIdle, Context context,
                 BrightnessRangeController brightnessRangeController,
                 BrightnessThrottler brightnessThrottler, int ambientLightHorizonShort,
-                int ambientLightHorizonLong, float userLux, float userNits) {
+                int ambientLightHorizonLong, float userLux, float userNits,
+                BrightnessClamperController brightnessClamperController) {
             return mAutomaticBrightnessController;
         }
 
diff --git a/services/tests/displayservicetests/src/com/android/server/display/brightness/clamper/BrightnessLowLuxModifierTest.kt b/services/tests/displayservicetests/src/com/android/server/display/brightness/clamper/BrightnessLowLuxModifierTest.kt
index ac7d1f5..e4a7d98 100644
--- a/services/tests/displayservicetests/src/com/android/server/display/brightness/clamper/BrightnessLowLuxModifierTest.kt
+++ b/services/tests/displayservicetests/src/com/android/server/display/brightness/clamper/BrightnessLowLuxModifierTest.kt
@@ -65,7 +65,7 @@
         Settings.Secure.putIntForUser(context.contentResolver,
                 Settings.Secure.EVEN_DIMMER_ACTIVATED, 1, userId)
         Settings.Secure.putFloatForUser(context.contentResolver,
-                Settings.Secure.EVEN_DIMMER_MIN_NITS, 0.7f, userId)
+                Settings.Secure.EVEN_DIMMER_MIN_NITS, 30.0f, userId)
         modifier.recalculateLowerBound()
         testHandler.flush()
         assertThat(modifier.isActive).isTrue()
@@ -81,11 +81,22 @@
                 Settings.Secure.EVEN_DIMMER_ACTIVATED, 1, userId)
         Settings.Secure.putFloatForUser(context.contentResolver,
                 Settings.Secure.EVEN_DIMMER_MIN_NITS, 0.0f, userId)
-        modifier.recalculateLowerBound()
+        modifier.onAmbientLuxChange(3000.0f)
         testHandler.flush()
         assertThat(modifier.isActive).isTrue()
 
         // Test restriction from lux setting
         assertThat(modifier.brightnessReason).isEqualTo(BrightnessReason.MODIFIER_MIN_LUX)
     }
+
+    @Test
+    fun testSettingOffDisablesModifier() {
+        Settings.Secure.putIntForUser(context.contentResolver,
+            Settings.Secure.EVEN_DIMMER_ACTIVATED, 0, userId)
+        assertThat(modifier.brightnessLowerBound).isEqualTo(PowerManager.BRIGHTNESS_MIN)
+        modifier.onAmbientLuxChange(3000.0f)
+        testHandler.flush()
+        assertThat(modifier.isActive).isFalse()
+        assertThat(modifier.brightnessLowerBound).isEqualTo(PowerManager.BRIGHTNESS_MIN)
+    }
 }