Remember brightness for the session

app/src/main/java/org/schabi/newpipe/player/MainVideoPlayer.java

@@ -119,6 +119,10 @@ public final class MainVideoPlayer extends AppCompatActivity
         if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) getWindow().setStatusBarColor(Color.BLACK);
         setVolumeControlStream(AudioManager.STREAM_MUSIC);
 
+        WindowManager.LayoutParams lp = getWindow().getAttributes();
+        lp.screenBrightness = PlayerHelper.getScreenBrightness(getApplicationContext());
+        getWindow().setAttributes(lp);
+
         hideSystemUi();
         setContentView(R.layout.activity_main_player);
         playerImpl = new VideoPlayerImpl(this);
@@ -205,6 +209,9 @@ public final class MainVideoPlayer extends AppCompatActivity
         if (DEBUG) Log.d(TAG, "onStop() called");
         super.onStop();
         playerImpl.destroy();
+
+        PlayerHelper.setScreenBrightness(getApplicationContext(),
+                getWindow().getAttributes().screenBrightness);
     }
 
     /*//////////////////////////////////////////////////////////////////////////
@@ -884,7 +891,9 @@ public final class MainVideoPlayer extends AppCompatActivity
         private final boolean isPlayerGestureEnabled = PlayerHelper.isPlayerGestureEnabled(getApplicationContext());
 
         private final float stepsBrightness = 15, stepBrightness = (1f / stepsBrightness), minBrightness = .01f;
-        private float currentBrightness = .5f;
+        private float currentBrightness = getWindow().getAttributes().screenBrightness > 0
+                ? getWindow().getAttributes().screenBrightness
+                : 0.5f;
 
         private int currentVolume, maxVolume = playerImpl.getAudioReactor().getMaxVolume();
         private final float stepsVolume = 15, stepVolume = (float) Math.ceil(maxVolume / stepsVolume), minVolume = 0;

app/src/main/java/org/schabi/newpipe/player/helper/PlayerHelper.java

@@ -9,9 +9,9 @@ import android.support.annotation.Nullable;
 import android.view.accessibility.CaptioningManager;
 
 import com.google.android.exoplayer2.SeekParameters;
+import com.google.android.exoplayer2.text.CaptionStyleCompat;
 import com.google.android.exoplayer2.trackselection.AdaptiveTrackSelection;
 import com.google.android.exoplayer2.trackselection.TrackSelection;
-import com.google.android.exoplayer2.text.CaptionStyleCompat;
 import com.google.android.exoplayer2.ui.AspectRatioFrameLayout;
 import com.google.android.exoplayer2.upstream.BandwidthMeter;
 import com.google.android.exoplayer2.util.MimeTypes;
@@ -37,6 +37,7 @@ import java.util.HashSet;
 import java.util.List;
 import java.util.Locale;
 import java.util.Set;
+import java.util.concurrent.TimeUnit;
 
 import static com.google.android.exoplayer2.ui.AspectRatioFrameLayout.RESIZE_MODE_FILL;
 import static com.google.android.exoplayer2.ui.AspectRatioFrameLayout.RESIZE_MODE_FIT;
@@ -260,6 +261,16 @@ public class PlayerHelper {
 
         return captioningManager.getFontScale();
     }
+
+    public static float getScreenBrightness(@NonNull final Context context) {
+        //a value of less than 0, the default, means to use the preferred screen brightness
+        return getScreenBrightness(context, -1);
+    }
+
+    public static void setScreenBrightness(@NonNull final Context context, final float setScreenBrightness) {
+        setScreenBrightness(context, setScreenBrightness, System.currentTimeMillis());
+    }
+
     ////////////////////////////////////////////////////////////////////////////
     // Private helpers
     ////////////////////////////////////////////////////////////////////////////
@@ -292,4 +303,23 @@ public class PlayerHelper {
     private static boolean isAutoQueueEnabled(@NonNull final Context context, final boolean b) {
         return getPreferences(context).getBoolean(context.getString(R.string.auto_queue_key), b);
     }
+
+    private static void setScreenBrightness(@NonNull final Context context, final float screenBrightness, final long timestamp) {
+        SharedPreferences.Editor editor = getPreferences(context).edit();
+        editor.putFloat(context.getString(R.string.screen_brightness_key), screenBrightness);
+        editor.putLong(context.getString(R.string.screen_brightness_timestamp_key), timestamp);
+        editor.apply();
+    }
+
+    private static float getScreenBrightness(@NonNull final Context context, final float screenBrightness) {
+        SharedPreferences sp = getPreferences(context);
+        long timestamp = sp.getLong(context.getString(R.string.screen_brightness_timestamp_key), 0);
+        // hypothesis: 4h covers a viewing block, eg evening. External lightning conditions will change in the next
+        // viewing block so we fall back to the default brightness
+        if ((System.currentTimeMillis() - timestamp) > TimeUnit.HOURS.toMillis(4)) {
+            return screenBrightness;
+        } else {
+            return sp.getFloat(context.getString(R.string.screen_brightness_key), screenBrightness);
+        }
+    }
 }

app/src/main/res/values/settings_keys.xml

@@ -22,6 +22,8 @@
     <string name="popup_remember_size_pos_key" translatable="false">popup_remember_size_pos_key</string>
     <string name="use_inexact_seek_key" translatable="false">use_inexact_seek_key</string>
     <string name="auto_queue_key" translatable="false">auto_queue_key</string>
+    <string name="screen_brightness_key" translatable="false">screen_brightness_key</string>
+    <string name="screen_brightness_timestamp_key" translatable="false">screen_brightness_timestamp_key</string>
 
     <string name="default_resolution_key" translatable="false">default_resolution</string>
     <string name="default_resolution_value" translatable="false">360p</string>