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/*
* Copyright (C) 2012 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.power;
import com.android.server.LightsService;
import java.util.concurrent.Executor;
/**
* Sets the value of a light asynchronously.
*
* This is done to avoid blocking the looper on devices for which
* setting the backlight brightness is especially slow.
*/
final class PhotonicModulator {
private static final int UNKNOWN_LIGHT_VALUE = -1;
private final Object mLock = new Object();
private final LightsService.Light mLight;
private final Executor mExecutor;
private final SuspendBlocker mSuspendBlocker;
private boolean mPendingChange;
private int mPendingLightValue;
private int mActualLightValue;
public PhotonicModulator(Executor executor, LightsService.Light light,
SuspendBlocker suspendBlocker) {
mExecutor = executor;
mLight = light;
mSuspendBlocker = suspendBlocker;
mPendingLightValue = UNKNOWN_LIGHT_VALUE;
mActualLightValue = UNKNOWN_LIGHT_VALUE;
}
/**
* Sets the backlight brightness, synchronously or asynchronously.
*
* @param lightValue The new light value, from 0 to 255.
* @param sync If true, waits for the brightness change to complete before returning.
*/
public void setBrightness(int lightValue, boolean sync) {
synchronized (mLock) {
if (lightValue != mPendingLightValue) {
mPendingLightValue = lightValue;
if (!mPendingChange) {
mPendingChange = true;
mSuspendBlocker.acquire();
mExecutor.execute(mTask);
}
}
if (sync) {
while (mPendingChange) {
try {
mLock.wait();
} catch (InterruptedException ex) {
// ignore it
}
}
}
}
}
private final Runnable mTask = new Runnable() {
@Override
public void run() {
for (;;) {
final int newLightValue;
synchronized (mLock) {
newLightValue = mPendingLightValue;
if (newLightValue == mActualLightValue) {
mSuspendBlocker.release();
mPendingChange = false;
mLock.notifyAll();
return;
}
mActualLightValue = newLightValue;
}
mLight.setBrightness(newLightValue);
}
}
};
}
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