/*
* Copyright (C) 2016 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.android.server.display;
import android.util.Slog;
/**
* A helper class for handling access to illuminance level values.
*/
final class LuxLevels {
private static final String TAG = "LuxLevels";
private static final boolean DEBUG = true;
private final float[] mBrightLevels;
private final float[] mDarkLevels;
private final float[] mLuxHysteresisLevels;
private final float[] mDozeBrightnessBacklightValues;
private final float[] mDozeSensorLuxLevels;
/**
* Creates a {@code LuxLevels} object with the given integer arrays. The following arrays
* are either empty or have the following relations:
* {@code brightLevels} and {@code darkLevels} have the same length n.
* {@code luxLevels} has length n+1.
*
* {@code dozeSensorLuxLevels} has length r.
* {@code dozeBrightnessBacklightValues} has length r+1.
*
* @param brightLevels an array of brightening hysteresis constraint constants
* @param darkLevels an array of darkening hysteresis constraint constants
* @param luxHysteresisLevels a monotonically increasing array of illuminance thresholds in lux
* @param dozeSensorLuxLevels a monotonically increasing array of ALS thresholds in lux
* @param dozeBrightnessBacklightValues an array of screen brightness values for doze mode in lux
*/
public LuxLevels(int[] brightLevels, int[] darkLevels, int[] luxHysteresisLevels,
int[] dozeSensorLuxLevels, int[] dozeBrightnessBacklightValues) {
if (brightLevels.length != darkLevels.length ||
darkLevels.length !=luxHysteresisLevels.length + 1) {
throw new IllegalArgumentException("Mismatch between hysteresis array lengths.");
}
if (dozeBrightnessBacklightValues.length > 0 && dozeSensorLuxLevels.length > 0
&& dozeBrightnessBacklightValues.length != dozeSensorLuxLevels.length + 1) {
throw new IllegalArgumentException("Mismatch between doze lux array lengths.");
}
mBrightLevels = setArrayFormat(brightLevels, 1000.0f);
mDarkLevels = setArrayFormat(darkLevels, 1000.0f);
mLuxHysteresisLevels = setArrayFormat(luxHysteresisLevels, 1.0f);
mDozeSensorLuxLevels = setArrayFormat(dozeSensorLuxLevels, 1.0f);
mDozeBrightnessBacklightValues = setArrayFormat(dozeBrightnessBacklightValues, 1.0f);
}
/**
* Return the brightening hysteresis threshold for the given lux level.
*/
public float getBrighteningThreshold(float lux) {
float brightConstant = getReferenceLevel(lux, mBrightLevels, mLuxHysteresisLevels);
float brightThreshold = lux * (1.0f + brightConstant);
if (DEBUG) {
Slog.d(TAG, "bright hysteresis constant= " + brightConstant + ", threshold="
+ brightThreshold + ", lux=" + lux);
}
return brightThreshold;
}
/**
* Return the darkening hysteresis threshold for the given lux level.
*/
public float getDarkeningThreshold(float lux) {
float darkConstant = getReferenceLevel(lux, mDarkLevels, mLuxHysteresisLevels);
float darkThreshold = lux * (1.0f - darkConstant);
if (DEBUG) {
Slog.d(TAG, "dark hysteresis constant= " + darkConstant + ", threshold="
+ darkThreshold + ", lux=" + lux);
}
return darkThreshold;
}
/**
* Return the doze backlight brightness level for the given ambient sensor lux level.
*/
public int getDozeBrightness(float lux) {
int dozeBrightness = (int) getReferenceLevel(lux, mDozeBrightnessBacklightValues,
mDozeSensorLuxLevels);
if (DEBUG) {
Slog.d(TAG, "doze brightness: " + dozeBrightness + ", lux=" + lux);
}
return dozeBrightness;
}
/**
* Find the index of the closest value in {@code thresholdLevels} to {@code lux} and return
* the {@code referenceLevels} entry with that index.
*/
private float getReferenceLevel(float lux, float[] referenceLevels, float[] thresholdLevels) {
int index = 0;
while (thresholdLevels.length > index && lux >= thresholdLevels[index]) {
++index;
}
return referenceLevels[index];
}
/**
* Return if the doze backlight brightness level is specified dynamically.
*/
public boolean hasDynamicDozeBrightness() {
return mDozeSensorLuxLevels.length > 0;
}
/**
* Return a float array where each i-th element equals {@code configArray[i]/divideFactor}.
*/
private float[] setArrayFormat(int[] configArray, float divideFactor) {
float[] levelArray = new float[configArray.length];
for (int index = 0; levelArray.length > index; ++index) {
levelArray[index] = (float)configArray[index] / divideFactor;
}
return levelArray;
}
}