com/android/server/display/DisplayDeviceConfig.java

/*
 * Copyright (C) 2020 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.os.Environment;
import android.util.Slog;

import com.android.server.display.config.DisplayConfiguration;
import com.android.server.display.config.NitsMap;
import com.android.server.display.config.Point;
import com.android.server.display.config.XmlParser;

import org.xmlpull.v1.XmlPullParserException;

import java.io.BufferedInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.List;

import javax.xml.datatype.DatatypeConfigurationException;

/**
 * Reads and stores display-specific configurations.
 */
public class DisplayDeviceConfig {
    private static final String TAG = "DisplayDeviceConfig";

    public static final float HIGH_BRIGHTNESS_MODE_UNSUPPORTED = Float.NaN;

    private static final String ETC_DIR = "etc";
    private static final String DISPLAY_CONFIG_DIR = "displayconfig";
    private static final String CONFIG_FILE_FORMAT = "display_%d.xml";

    private float[] mNits;
    private float[] mBrightness;

    private DisplayDeviceConfig() {
    }

    /**
     * Creates an instance for the specified display.
     *
     * @param physicalDisplayId The display ID for which to load the configuration.
     * @return A configuration instance for the specified display.
     */
    public static DisplayDeviceConfig create(long physicalDisplayId) {
        final DisplayDeviceConfig config = new DisplayDeviceConfig();
        final String filename = String.format(CONFIG_FILE_FORMAT, physicalDisplayId);

        config.initFromFile(Environment.buildPath(
                Environment.getProductDirectory(), ETC_DIR, DISPLAY_CONFIG_DIR, filename));
        return config;
    }

    /**
     * Return the brightness mapping nits array if one is defined in the configuration file.
     *
     * @return The brightness mapping nits array.
     */
    public float[] getNits() {
        return mNits;
    }

    /**
     * Return the brightness mapping value array if one is defined in the configuration file.
     *
     * @return The brightness mapping value array.
     */
    public float[] getBrightness() {
        return mBrightness;
    }

    private void initFromFile(File configFile) {
        if (!configFile.exists()) {
            // Display configuration files aren't required to exist.
            return;
        }

        if (!configFile.isFile()) {
            Slog.e(TAG, "Display configuration is not a file: " + configFile + ", skipping");
            return;
        }

        try (InputStream in = new BufferedInputStream(new FileInputStream(configFile))) {
            final DisplayConfiguration config = XmlParser.read(in);
            loadBrightnessMap(config);
        } catch (IOException | DatatypeConfigurationException | XmlPullParserException e) {
            Slog.e(TAG, "Encountered an error while reading/parsing display config file: "
                    + configFile, e);
        }
    }

    private void loadBrightnessMap(DisplayConfiguration config) {
        final NitsMap map = config.getScreenBrightnessMap();
        final List<Point> points = map.getPoint();
        final int size = points.size();

        float[] nits = new float[size];
        float[] backlight = new float[size];

        int i = 0;
        for (Point point : points) {
            nits[i] = point.getNits().floatValue();
            backlight[i] = point.getValue().floatValue();
            if (i > 0) {
                if (nits[i] < nits[i - 1]) {
                    Slog.e(TAG, "screenBrightnessMap must be non-decreasing, ignoring rest "
                            + " of configuration. Nits: " +  nits[i] + " < " + nits[i - 1]);
                    return;
                }

                if (backlight[i] < backlight[i - 1]) {
                    Slog.e(TAG, "screenBrightnessMap must be non-decreasing, ignoring rest "
                            + " of configuration. Value: " +  backlight[i] + " < "
                            + backlight[i - 1]);
                    return;
                }
            }
            ++i;
        }
        mNits = nits;
        mBrightness = backlight;
    }
}