services/surfaceflinger/RegionSamplingThread.cpp - android_frameworks_native - Gitiles

 /*
  * Copyright 2019 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.
  */

 //#define LOG_NDEBUG 0
 #define ATRACE_TAG ATRACE_TAG_GRAPHICS
 #undef LOG_TAG
 #define LOG_TAG "RegionSamplingThread"

 #include "RegionSamplingThread.h"

 #include <cutils/properties.h>
 #include <gui/IRegionSamplingListener.h>
 #include <utils/Trace.h>
 #include <string>

 #include <compositionengine/Display.h>
 #include <compositionengine/impl/OutputCompositionState.h>
 #include "DisplayDevice.h"
 #include "Layer.h"
 #include "SurfaceFlinger.h"

 namespace android {
 using namespace std::chrono_literals;

 template <typename T>
 struct SpHash {
     size_t operator()(const sp<T>& p) const { return std::hash<T*>()(p.get()); }
 };

 constexpr auto lumaSamplingStepTag = "LumaSamplingStep";
 enum class samplingStep {
     noWorkNeeded,
     idleTimerWaiting,
     waitForZeroPhase,
     waitForSamplePhase,
     sample
 };

 constexpr auto defaultRegionSamplingOffset = -3ms;
 constexpr auto defaultRegionSamplingPeriod = 100ms;
 constexpr auto defaultRegionSamplingTimerTimeout = 100ms;
 // TODO: (b/127403193) duration to string conversion could probably be constexpr
 template <typename Rep, typename Per>
 inline std::string toNsString(std::chrono::duration<Rep, Per> t) {
     return std::to_string(std::chrono::duration_cast<std::chrono::nanoseconds>(t).count());
 }

 RegionSamplingThread::EnvironmentTimingTunables::EnvironmentTimingTunables() {
     char value[PROPERTY_VALUE_MAX] = {};

     property_get("debug.sf.region_sampling_offset_ns", value,
                  toNsString(defaultRegionSamplingOffset).c_str());
     int const samplingOffsetNsRaw = atoi(value);

     property_get("debug.sf.region_sampling_period_ns", value,
                  toNsString(defaultRegionSamplingPeriod).c_str());
     int const samplingPeriodNsRaw = atoi(value);

     property_get("debug.sf.region_sampling_timer_timeout_ns", value,
                  toNsString(defaultRegionSamplingTimerTimeout).c_str());
     int const samplingTimerTimeoutNsRaw = atoi(value);

     if ((samplingPeriodNsRaw < 0) || (samplingTimerTimeoutNsRaw < 0)) {
         ALOGW("User-specified sampling tuning options nonsensical. Using defaults");
         mSamplingOffset = defaultRegionSamplingOffset;
         mSamplingPeriod = defaultRegionSamplingPeriod;
         mSamplingTimerTimeout = defaultRegionSamplingTimerTimeout;
     } else {
         mSamplingOffset = std::chrono::nanoseconds(samplingOffsetNsRaw);
         mSamplingPeriod = std::chrono::nanoseconds(samplingPeriodNsRaw);
         mSamplingTimerTimeout = std::chrono::nanoseconds(samplingTimerTimeoutNsRaw);
     }
 }

 struct SamplingOffsetCallback : DispSync::Callback {
     SamplingOffsetCallback(RegionSamplingThread& samplingThread, Scheduler& scheduler,
                            std::chrono::nanoseconds targetSamplingOffset)
           : mRegionSamplingThread(samplingThread),
             mScheduler(scheduler),
             mTargetSamplingOffset(targetSamplingOffset) {}

     ~SamplingOffsetCallback() { stopVsyncListener(); }

     SamplingOffsetCallback(const SamplingOffsetCallback&) = delete;
     SamplingOffsetCallback& operator=(const SamplingOffsetCallback&) = delete;

     void startVsyncListener() {
         std::lock_guard lock(mMutex);
         if (mVsyncListening) return;

         mPhaseIntervalSetting = Phase::ZERO;
         mScheduler.withPrimaryDispSync([this](android::DispSync& sync) {
             sync.addEventListener("SamplingThreadDispSyncListener", 0, this, mLastCallbackTime);
         });
         mVsyncListening = true;
     }

     void stopVsyncListener() {
         std::lock_guard lock(mMutex);
         stopVsyncListenerLocked();
     }

 private:
     void stopVsyncListenerLocked() /*REQUIRES(mMutex)*/ {
         if (!mVsyncListening) return;

         mScheduler.withPrimaryDispSync([this](android::DispSync& sync) {
             sync.removeEventListener(this, &mLastCallbackTime);
         });
         mVsyncListening = false;
     }

     void onDispSyncEvent(nsecs_t /* when */) final {
         std::unique_lock<decltype(mMutex)> lock(mMutex);

         if (mPhaseIntervalSetting == Phase::ZERO) {
             ATRACE_INT(lumaSamplingStepTag, static_cast<int>(samplingStep::waitForSamplePhase));
             mPhaseIntervalSetting = Phase::SAMPLING;
             mScheduler.withPrimaryDispSync([this](android::DispSync& sync) {
                 sync.changePhaseOffset(this, mTargetSamplingOffset.count());
             });
             return;
         }

         if (mPhaseIntervalSetting == Phase::SAMPLING) {
             mPhaseIntervalSetting = Phase::ZERO;
             mScheduler.withPrimaryDispSync(
                     [this](android::DispSync& sync) { sync.changePhaseOffset(this, 0); });
             stopVsyncListenerLocked();
             lock.unlock();
             mRegionSamplingThread.notifySamplingOffset();
             return;
         }
     }

     RegionSamplingThread& mRegionSamplingThread;
     Scheduler& mScheduler;
     const std::chrono::nanoseconds mTargetSamplingOffset;
     mutable std::mutex mMutex;
     nsecs_t mLastCallbackTime = 0;
     enum class Phase {
         ZERO,
         SAMPLING
     } mPhaseIntervalSetting /*GUARDED_BY(mMutex) macro doesnt work with unique_lock?*/
             = Phase::ZERO;
     bool mVsyncListening /*GUARDED_BY(mMutex)*/ = false;
 };

 RegionSamplingThread::RegionSamplingThread(SurfaceFlinger& flinger, Scheduler& scheduler,
                                            const TimingTunables& tunables)
       : mFlinger(flinger),
         mScheduler(scheduler),
         mTunables(tunables),
         mIdleTimer(std::chrono::duration_cast<std::chrono::milliseconds>(
                            mTunables.mSamplingTimerTimeout),
                    [] {}, [this] { checkForStaleLuma(); }),
         mPhaseCallback(std::make_unique<SamplingOffsetCallback>(*this, mScheduler,
                                                                 tunables.mSamplingOffset)),
         lastSampleTime(0ns) {
     mThread = std::thread([this]() { threadMain(); });
     pthread_setname_np(mThread.native_handle(), "RegionSamplingThread");
     mIdleTimer.start();
 }

 RegionSamplingThread::RegionSamplingThread(SurfaceFlinger& flinger, Scheduler& scheduler)
       : RegionSamplingThread(flinger, scheduler,
                              TimingTunables{defaultRegionSamplingOffset,
                                             defaultRegionSamplingPeriod,
                                             defaultRegionSamplingTimerTimeout}) {}

 RegionSamplingThread::~RegionSamplingThread() {
     mIdleTimer.stop();

     {
         std::lock_guard lock(mThreadControlMutex);
         mRunning = false;
         mCondition.notify_one();
     }

     if (mThread.joinable()) {
         mThread.join();
     }
 }

 void RegionSamplingThread::addListener(const Rect& samplingArea, const sp<IBinder>& stopLayerHandle,
                                        const sp<IRegionSamplingListener>& listener) {
     wp<Layer> stopLayer = stopLayerHandle != nullptr
             ? static_cast<Layer::Handle*>(stopLayerHandle.get())->owner
             : nullptr;

     sp<IBinder> asBinder = IInterface::asBinder(listener);
     asBinder->linkToDeath(this);
     std::lock_guard lock(mSamplingMutex);
     mDescriptors.emplace(wp<IBinder>(asBinder), Descriptor{samplingArea, stopLayer, listener});
 }

 void RegionSamplingThread::removeListener(const sp<IRegionSamplingListener>& listener) {
     std::lock_guard lock(mSamplingMutex);
     mDescriptors.erase(wp<IBinder>(IInterface::asBinder(listener)));
 }

 void RegionSamplingThread::checkForStaleLuma() {
     std::lock_guard lock(mThreadControlMutex);

     if (mDiscardedFrames) {
         ATRACE_INT(lumaSamplingStepTag, static_cast<int>(samplingStep::waitForZeroPhase));
         mDiscardedFrames = false;
         mPhaseCallback->startVsyncListener();
     }
 }

 void RegionSamplingThread::notifyNewContent() {
     doSample();
 }

 void RegionSamplingThread::notifySamplingOffset() {
     doSample();
 }

 void RegionSamplingThread::doSample() {
     std::lock_guard lock(mThreadControlMutex);
     auto now = std::chrono::nanoseconds(systemTime(SYSTEM_TIME_MONOTONIC));
     if (lastSampleTime + mTunables.mSamplingPeriod > now) {
         ATRACE_INT(lumaSamplingStepTag, static_cast<int>(samplingStep::idleTimerWaiting));
         mDiscardedFrames = true;
         return;
     }

     ATRACE_INT(lumaSamplingStepTag, static_cast<int>(samplingStep::sample));

     mDiscardedFrames = false;
     lastSampleTime = now;

     mIdleTimer.reset();
     mPhaseCallback->stopVsyncListener();

     mSampleRequested = true;
     mCondition.notify_one();
 }

 void RegionSamplingThread::binderDied(const wp<IBinder>& who) {
     std::lock_guard lock(mSamplingMutex);
     mDescriptors.erase(who);
 }

 namespace {
 // Using Rec. 709 primaries
 float getLuma(float r, float g, float b) {
     constexpr auto rec709_red_primary = 0.2126f;
     constexpr auto rec709_green_primary = 0.7152f;
     constexpr auto rec709_blue_primary = 0.0722f;
     return rec709_red_primary * r + rec709_green_primary * g + rec709_blue_primary * b;
 }
 } // anonymous namespace

 float sampleArea(const uint32_t* data, int32_t width, int32_t height, int32_t stride,
                  uint32_t orientation, const Rect& sample_area) {
     if (!sample_area.isValid() || (sample_area.getWidth() > width) ||
         (sample_area.getHeight() > height)) {
         ALOGE("invalid sampling region requested");
         return 0.0f;
     }

     // (b/133849373) ROT_90 screencap images produced upside down
     auto area = sample_area;
     if (orientation & ui::Transform::ROT_90) {
         area.top = height - area.top;
         area.bottom = height - area.bottom;
         std::swap(area.top, area.bottom);

         area.left = width - area.left;
         area.right = width - area.right;
         std::swap(area.left, area.right);
     }

     std::array<int32_t, 256> brightnessBuckets = {};
     const int32_t majoritySampleNum = area.getWidth() * area.getHeight() / 2;

     for (int32_t row = area.top; row < area.bottom; ++row) {
         const uint32_t* rowBase = data + row * stride;
         for (int32_t column = area.left; column < area.right; ++column) {
             uint32_t pixel = rowBase[column];
             const float r = (pixel & 0xFF) / 255.0f;
             const float g = ((pixel >> 8) & 0xFF) / 255.0f;
             const float b = ((pixel >> 16) & 0xFF) / 255.0f;
             const uint8_t luma = std::round(getLuma(r, g, b) * 255.0f);
             ++brightnessBuckets[luma];
             if (brightnessBuckets[luma] > majoritySampleNum) return luma / 255.0f;
         }
     }

     int32_t accumulated = 0;
     size_t bucket = 0;
     for (; bucket < brightnessBuckets.size(); bucket++) {
         accumulated += brightnessBuckets[bucket];
         if (accumulated > majoritySampleNum) break;
     }

     return bucket / 255.0f;
 }

 std::vector<float> RegionSamplingThread::sampleBuffer(
         const sp<GraphicBuffer>& buffer, const Point& leftTop,
         const std::vector<RegionSamplingThread::Descriptor>& descriptors, uint32_t orientation) {
     void* data_raw = nullptr;
     buffer->lock(GRALLOC_USAGE_SW_READ_OFTEN, &data_raw);
     std::shared_ptr<uint32_t> data(reinterpret_cast<uint32_t*>(data_raw),
                                    [&buffer](auto) { buffer->unlock(); });
     if (!data) return {};

     const int32_t width = buffer->getWidth();
     const int32_t height = buffer->getHeight();
     const int32_t stride = buffer->getStride();
     std::vector<float> lumas(descriptors.size());
     std::transform(descriptors.begin(), descriptors.end(), lumas.begin(),
                    [&](auto const& descriptor) {
                        return sampleArea(data.get(), width, height, stride, orientation,
                                          descriptor.area - leftTop);
                    });
     return lumas;
 }

 void RegionSamplingThread::captureSample() {
     ATRACE_CALL();
     std::lock_guard lock(mSamplingMutex);

     if (mDescriptors.empty()) {
         return;
     }

     const auto device = mFlinger.getDefaultDisplayDevice();
     const auto display = device->getCompositionDisplay();
     const auto state = display->getState();
     const auto orientation = static_cast<ui::Transform::orientation_flags>(state.orientation);

     std::vector<RegionSamplingThread::Descriptor> descriptors;
     Region sampleRegion;
     for (const auto& [listener, descriptor] : mDescriptors) {
         sampleRegion.orSelf(descriptor.area);
         descriptors.emplace_back(descriptor);
     }

     const Rect sampledArea = sampleRegion.bounds();

     auto dx = 0;
     auto dy = 0;
     switch (orientation) {
         case ui::Transform::ROT_90:
             dx = device->getWidth();
             break;
         case ui::Transform::ROT_180:
             dx = device->getWidth();
             dy = device->getHeight();
             break;
         case ui::Transform::ROT_270:
             dy = device->getHeight();
             break;
         default:
             break;
     }

     ui::Transform t(orientation);
     auto screencapRegion = t.transform(sampleRegion);
     screencapRegion = screencapRegion.translate(dx, dy);
     DisplayRenderArea renderArea(device, screencapRegion.bounds(), sampledArea.getWidth(),
                                  sampledArea.getHeight(), ui::Dataspace::V0_SRGB, orientation);

     std::unordered_set<sp<IRegionSamplingListener>, SpHash<IRegionSamplingListener>> listeners;

     auto traverseLayers = [&](const LayerVector::Visitor& visitor) {
         bool stopLayerFound = false;
         auto filterVisitor = [&](Layer* layer) {
             // We don't want to capture any layers beyond the stop layer
             if (stopLayerFound) return;

             // Likewise if we just found a stop layer, set the flag and abort
             for (const auto& [area, stopLayer, listener] : descriptors) {
                 if (layer == stopLayer.promote().get()) {
                     stopLayerFound = true;
                     return;
                 }
             }

             // Compute the layer's position on the screen
             const Rect bounds = Rect(layer->getBounds());
             const ui::Transform transform = layer->getTransform();
             constexpr bool roundOutwards = true;
             Rect transformed = transform.transform(bounds, roundOutwards);

             // If this layer doesn't intersect with the larger sampledArea, skip capturing it
             Rect ignore;
             if (!transformed.intersect(sampledArea, &ignore)) return;

             // If the layer doesn't intersect a sampling area, skip capturing it
             bool intersectsAnyArea = false;
             for (const auto& [area, stopLayer, listener] : descriptors) {
                 if (transformed.intersect(area, &ignore)) {
                     intersectsAnyArea = true;
                     listeners.insert(listener);
                 }
             }
             if (!intersectsAnyArea) return;

             ALOGV("Traversing [%s] [%d, %d, %d, %d]", layer->getName().string(), bounds.left,
                   bounds.top, bounds.right, bounds.bottom);
             visitor(layer);
         };
         mFlinger.traverseLayersInDisplay(device, filterVisitor);
     };

     sp<GraphicBuffer> buffer = nullptr;
     if (mCachedBuffer && mCachedBuffer->getWidth() == sampledArea.getWidth() &&
         mCachedBuffer->getHeight() == sampledArea.getHeight()) {
         buffer = mCachedBuffer;
     } else {
         const uint32_t usage = GRALLOC_USAGE_SW_READ_OFTEN | GRALLOC_USAGE_HW_RENDER;
         buffer = new GraphicBuffer(sampledArea.getWidth(), sampledArea.getHeight(),
                                    PIXEL_FORMAT_RGBA_8888, 1, usage, "RegionSamplingThread");
     }

     bool ignored;
     mFlinger.captureScreenCommon(renderArea, traverseLayers, buffer, false, ignored);

     std::vector<Descriptor> activeDescriptors;
     for (const auto& descriptor : descriptors) {
         if (listeners.count(descriptor.listener) != 0) {
             activeDescriptors.emplace_back(descriptor);
         }
     }

     ALOGV("Sampling %zu descriptors", activeDescriptors.size());
     std::vector<float> lumas =
             sampleBuffer(buffer, sampledArea.leftTop(), activeDescriptors, orientation);
     if (lumas.size() != activeDescriptors.size()) {
         ALOGW("collected %zu median luma values for %zu descriptors", lumas.size(),
               activeDescriptors.size());
         return;
     }

     for (size_t d = 0; d < activeDescriptors.size(); ++d) {
         activeDescriptors[d].listener->onSampleCollected(lumas[d]);
     }

     // Extend the lifetime of mCachedBuffer from the previous frame to here to ensure that:
     // 1) The region sampling thread is the last owner of the buffer, and the freeing of the buffer
     // happens in this thread, as opposed to the main thread.
     // 2) The listener(s) receive their notifications prior to freeing the buffer.
     mCachedBuffer = buffer;
     ATRACE_INT(lumaSamplingStepTag, static_cast<int>(samplingStep::noWorkNeeded));
 }

 // NO_THREAD_SAFETY_ANALYSIS is because std::unique_lock presently lacks thread safety annotations.
 void RegionSamplingThread::threadMain() NO_THREAD_SAFETY_ANALYSIS {
     std::unique_lock<std::mutex> lock(mThreadControlMutex);
     while (mRunning) {
         if (mSampleRequested) {
             mSampleRequested = false;
             lock.unlock();
             captureSample();
             lock.lock();
         }
         mCondition.wait(lock, [this]() REQUIRES(mThreadControlMutex) {
             return mSampleRequested || !mRunning;
         });
     }
 }

 } // namespace android
	/*
	* Copyright 2019 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.
	*/

	//#define LOG_NDEBUG 0
	#define ATRACE_TAG ATRACE_TAG_GRAPHICS
	#undef LOG_TAG
	#define LOG_TAG "RegionSamplingThread"

	#include "RegionSamplingThread.h"

	#include <cutils/properties.h>
	#include <gui/IRegionSamplingListener.h>
	#include <utils/Trace.h>
	#include <string>

	#include <compositionengine/Display.h>
	#include <compositionengine/impl/OutputCompositionState.h>
	#include "DisplayDevice.h"
	#include "Layer.h"
	#include "SurfaceFlinger.h"

	namespace android {
	using namespace std::chrono_literals;

	template <typename T>
	struct SpHash {
	size_t operator()(const sp<T>& p) const { return std::hash<T*>()(p.get()); }
	};

	constexpr auto lumaSamplingStepTag = "LumaSamplingStep";
	enum class samplingStep {
	noWorkNeeded,
	idleTimerWaiting,
	waitForZeroPhase,
	waitForSamplePhase,
	sample
	};

	constexpr auto defaultRegionSamplingOffset = -3ms;
	constexpr auto defaultRegionSamplingPeriod = 100ms;
	constexpr auto defaultRegionSamplingTimerTimeout = 100ms;
	// TODO: (b/127403193) duration to string conversion could probably be constexpr
	template <typename Rep, typename Per>
	inline std::string toNsString(std::chrono::duration<Rep, Per> t) {
	return std::to_string(std::chrono::duration_cast<std::chrono::nanoseconds>(t).count());
	}

	RegionSamplingThread::EnvironmentTimingTunables::EnvironmentTimingTunables() {
	char value[PROPERTY_VALUE_MAX] = {};

	property_get("debug.sf.region_sampling_offset_ns", value,
	toNsString(defaultRegionSamplingOffset).c_str());
	int const samplingOffsetNsRaw = atoi(value);

	property_get("debug.sf.region_sampling_period_ns", value,
	toNsString(defaultRegionSamplingPeriod).c_str());
	int const samplingPeriodNsRaw = atoi(value);

	property_get("debug.sf.region_sampling_timer_timeout_ns", value,
	toNsString(defaultRegionSamplingTimerTimeout).c_str());
	int const samplingTimerTimeoutNsRaw = atoi(value);

	if ((samplingPeriodNsRaw < 0) \|\| (samplingTimerTimeoutNsRaw < 0)) {
	ALOGW("User-specified sampling tuning options nonsensical. Using defaults");
	mSamplingOffset = defaultRegionSamplingOffset;
	mSamplingPeriod = defaultRegionSamplingPeriod;
	mSamplingTimerTimeout = defaultRegionSamplingTimerTimeout;
	} else {
	mSamplingOffset = std::chrono::nanoseconds(samplingOffsetNsRaw);
	mSamplingPeriod = std::chrono::nanoseconds(samplingPeriodNsRaw);
	mSamplingTimerTimeout = std::chrono::nanoseconds(samplingTimerTimeoutNsRaw);
	}
	}

	struct SamplingOffsetCallback : DispSync::Callback {
	SamplingOffsetCallback(RegionSamplingThread& samplingThread, Scheduler& scheduler,
	std::chrono::nanoseconds targetSamplingOffset)
	: mRegionSamplingThread(samplingThread),
	mScheduler(scheduler),
	mTargetSamplingOffset(targetSamplingOffset) {}

	~SamplingOffsetCallback() { stopVsyncListener(); }

	SamplingOffsetCallback(const SamplingOffsetCallback&) = delete;
	SamplingOffsetCallback& operator=(const SamplingOffsetCallback&) = delete;

	void startVsyncListener() {
	std::lock_guard lock(mMutex);
	if (mVsyncListening) return;

	mPhaseIntervalSetting = Phase::ZERO;
	mScheduler.withPrimaryDispSync([this](android::DispSync& sync) {
	sync.addEventListener("SamplingThreadDispSyncListener", 0, this, mLastCallbackTime);
	});
	mVsyncListening = true;
	}

	void stopVsyncListener() {
	std::lock_guard lock(mMutex);
	stopVsyncListenerLocked();
	}

	private:
	void stopVsyncListenerLocked() /REQUIRES(mMutex)/ {
	if (!mVsyncListening) return;

	mScheduler.withPrimaryDispSync([this](android::DispSync& sync) {
	sync.removeEventListener(this, &mLastCallbackTime);
	});
	mVsyncListening = false;
	}

	void onDispSyncEvent(nsecs_t /* when */) final {
	std::unique_lock<decltype(mMutex)> lock(mMutex);

	if (mPhaseIntervalSetting == Phase::ZERO) {
	ATRACE_INT(lumaSamplingStepTag, static_cast<int>(samplingStep::waitForSamplePhase));
	mPhaseIntervalSetting = Phase::SAMPLING;
	mScheduler.withPrimaryDispSync([this](android::DispSync& sync) {
	sync.changePhaseOffset(this, mTargetSamplingOffset.count());
	});
	return;
	}

	if (mPhaseIntervalSetting == Phase::SAMPLING) {
	mPhaseIntervalSetting = Phase::ZERO;
	mScheduler.withPrimaryDispSync(
	[this](android::DispSync& sync) { sync.changePhaseOffset(this, 0); });
	stopVsyncListenerLocked();
	lock.unlock();
	mRegionSamplingThread.notifySamplingOffset();
	return;
	}
	}

	RegionSamplingThread& mRegionSamplingThread;
	Scheduler& mScheduler;
	const std::chrono::nanoseconds mTargetSamplingOffset;
	mutable std::mutex mMutex;
	nsecs_t mLastCallbackTime = 0;
	enum class Phase {
	ZERO,
	SAMPLING
	} mPhaseIntervalSetting /GUARDED_BY(mMutex) macro doesnt work with unique_lock?/
	= Phase::ZERO;
	bool mVsyncListening /GUARDED_BY(mMutex)/ = false;
	};

	RegionSamplingThread::RegionSamplingThread(SurfaceFlinger& flinger, Scheduler& scheduler,
	const TimingTunables& tunables)
	: mFlinger(flinger),
	mScheduler(scheduler),
	mTunables(tunables),
	mIdleTimer(std::chrono::duration_cast<std::chrono::milliseconds>(
	mTunables.mSamplingTimerTimeout),
	[] {}, [this] { checkForStaleLuma(); }),
	mPhaseCallback(std::make_unique<SamplingOffsetCallback>(*this, mScheduler,
	tunables.mSamplingOffset)),
	lastSampleTime(0ns) {
	mThread = std::thread([this]() { threadMain(); });
	pthread_setname_np(mThread.native_handle(), "RegionSamplingThread");
	mIdleTimer.start();
	}

	RegionSamplingThread::RegionSamplingThread(SurfaceFlinger& flinger, Scheduler& scheduler)
	: RegionSamplingThread(flinger, scheduler,
	TimingTunables{defaultRegionSamplingOffset,
	defaultRegionSamplingPeriod,
	defaultRegionSamplingTimerTimeout}) {}

	RegionSamplingThread::~RegionSamplingThread() {
	mIdleTimer.stop();

	{
	std::lock_guard lock(mThreadControlMutex);
	mRunning = false;
	mCondition.notify_one();
	}

	if (mThread.joinable()) {
	mThread.join();
	}
	}

	void RegionSamplingThread::addListener(const Rect& samplingArea, const sp<IBinder>& stopLayerHandle,
	const sp<IRegionSamplingListener>& listener) {
	wp<Layer> stopLayer = stopLayerHandle != nullptr
	? static_cast<Layer::Handle*>(stopLayerHandle.get())->owner
	: nullptr;

	sp<IBinder> asBinder = IInterface::asBinder(listener);
	asBinder->linkToDeath(this);
	std::lock_guard lock(mSamplingMutex);
	mDescriptors.emplace(wp<IBinder>(asBinder), Descriptor{samplingArea, stopLayer, listener});
	}

	void RegionSamplingThread::removeListener(const sp<IRegionSamplingListener>& listener) {
	std::lock_guard lock(mSamplingMutex);
	mDescriptors.erase(wp<IBinder>(IInterface::asBinder(listener)));
	}

	void RegionSamplingThread::checkForStaleLuma() {
	std::lock_guard lock(mThreadControlMutex);

	if (mDiscardedFrames) {
	ATRACE_INT(lumaSamplingStepTag, static_cast<int>(samplingStep::waitForZeroPhase));
	mDiscardedFrames = false;
	mPhaseCallback->startVsyncListener();
	}
	}

	void RegionSamplingThread::notifyNewContent() {
	doSample();
	}

	void RegionSamplingThread::notifySamplingOffset() {
	doSample();
	}

	void RegionSamplingThread::doSample() {
	std::lock_guard lock(mThreadControlMutex);
	auto now = std::chrono::nanoseconds(systemTime(SYSTEM_TIME_MONOTONIC));
	if (lastSampleTime + mTunables.mSamplingPeriod > now) {
	ATRACE_INT(lumaSamplingStepTag, static_cast<int>(samplingStep::idleTimerWaiting));
	mDiscardedFrames = true;
	return;
	}

	ATRACE_INT(lumaSamplingStepTag, static_cast<int>(samplingStep::sample));

	mDiscardedFrames = false;
	lastSampleTime = now;

	mIdleTimer.reset();
	mPhaseCallback->stopVsyncListener();

	mSampleRequested = true;
	mCondition.notify_one();
	}

	void RegionSamplingThread::binderDied(const wp<IBinder>& who) {
	std::lock_guard lock(mSamplingMutex);
	mDescriptors.erase(who);
	}

	namespace {
	// Using Rec. 709 primaries
	float getLuma(float r, float g, float b) {
	constexpr auto rec709_red_primary = 0.2126f;
	constexpr auto rec709_green_primary = 0.7152f;
	constexpr auto rec709_blue_primary = 0.0722f;
	return rec709_red_primary * r + rec709_green_primary * g + rec709_blue_primary * b;
	}
	} // anonymous namespace

	float sampleArea(const uint32_t* data, int32_t width, int32_t height, int32_t stride,
	uint32_t orientation, const Rect& sample_area) {
	if (!sample_area.isValid() \|\| (sample_area.getWidth() > width) \|\|
	(sample_area.getHeight() > height)) {
	ALOGE("invalid sampling region requested");
	return 0.0f;
	}

	// (b/133849373) ROT_90 screencap images produced upside down
	auto area = sample_area;
	if (orientation & ui::Transform::ROT_90) {
	area.top = height - area.top;
	area.bottom = height - area.bottom;
	std::swap(area.top, area.bottom);

	area.left = width - area.left;
	area.right = width - area.right;
	std::swap(area.left, area.right);
	}

	std::array<int32_t, 256> brightnessBuckets = {};
	const int32_t majoritySampleNum = area.getWidth() * area.getHeight() / 2;

	for (int32_t row = area.top; row < area.bottom; ++row) {
	const uint32_t* rowBase = data + row * stride;
	for (int32_t column = area.left; column < area.right; ++column) {
	uint32_t pixel = rowBase[column];
	const float r = (pixel & 0xFF) / 255.0f;
	const float g = ((pixel >> 8) & 0xFF) / 255.0f;
	const float b = ((pixel >> 16) & 0xFF) / 255.0f;
	const uint8_t luma = std::round(getLuma(r, g, b) * 255.0f);
	++brightnessBuckets[luma];
	if (brightnessBuckets[luma] > majoritySampleNum) return luma / 255.0f;
	}
	}

	int32_t accumulated = 0;
	size_t bucket = 0;
	for (; bucket < brightnessBuckets.size(); bucket++) {
	accumulated += brightnessBuckets[bucket];
	if (accumulated > majoritySampleNum) break;
	}

	return bucket / 255.0f;
	}

	std::vector<float> RegionSamplingThread::sampleBuffer(
	const sp<GraphicBuffer>& buffer, const Point& leftTop,
	const std::vector<RegionSamplingThread::Descriptor>& descriptors, uint32_t orientation) {
	void* data_raw = nullptr;
	buffer->lock(GRALLOC_USAGE_SW_READ_OFTEN, &data_raw);
	std::shared_ptr<uint32_t> data(reinterpret_cast<uint32_t*>(data_raw),
	[&buffer](auto) { buffer->unlock(); });
	if (!data) return {};

	const int32_t width = buffer->getWidth();
	const int32_t height = buffer->getHeight();
	const int32_t stride = buffer->getStride();
	std::vector<float> lumas(descriptors.size());
	std::transform(descriptors.begin(), descriptors.end(), lumas.begin(),
	[&](auto const& descriptor) {
	return sampleArea(data.get(), width, height, stride, orientation,
	descriptor.area - leftTop);
	});
	return lumas;
	}

	void RegionSamplingThread::captureSample() {
	ATRACE_CALL();
	std::lock_guard lock(mSamplingMutex);

	if (mDescriptors.empty()) {
	return;
	}

	const auto device = mFlinger.getDefaultDisplayDevice();
	const auto display = device->getCompositionDisplay();
	const auto state = display->getState();
	const auto orientation = static_cast<ui::Transform::orientation_flags>(state.orientation);

	std::vector<RegionSamplingThread::Descriptor> descriptors;
	Region sampleRegion;
	for (const auto& [listener, descriptor] : mDescriptors) {
	sampleRegion.orSelf(descriptor.area);
	descriptors.emplace_back(descriptor);
	}

	const Rect sampledArea = sampleRegion.bounds();

	auto dx = 0;
	auto dy = 0;
	switch (orientation) {
	case ui::Transform::ROT_90:
	dx = device->getWidth();
	break;
	case ui::Transform::ROT_180:
	dx = device->getWidth();
	dy = device->getHeight();
	break;
	case ui::Transform::ROT_270:
	dy = device->getHeight();
	break;
	default:
	break;
	}

	ui::Transform t(orientation);
	auto screencapRegion = t.transform(sampleRegion);
	screencapRegion = screencapRegion.translate(dx, dy);
	DisplayRenderArea renderArea(device, screencapRegion.bounds(), sampledArea.getWidth(),
	sampledArea.getHeight(), ui::Dataspace::V0_SRGB, orientation);

	std::unordered_set<sp<IRegionSamplingListener>, SpHash<IRegionSamplingListener>> listeners;

	auto traverseLayers = [&](const LayerVector::Visitor& visitor) {
	bool stopLayerFound = false;
	auto filterVisitor = [&](Layer* layer) {
	// We don't want to capture any layers beyond the stop layer
	if (stopLayerFound) return;

	// Likewise if we just found a stop layer, set the flag and abort
	for (const auto& [area, stopLayer, listener] : descriptors) {
	if (layer == stopLayer.promote().get()) {
	stopLayerFound = true;
	return;
	}
	}

	// Compute the layer's position on the screen
	const Rect bounds = Rect(layer->getBounds());
	const ui::Transform transform = layer->getTransform();
	constexpr bool roundOutwards = true;
	Rect transformed = transform.transform(bounds, roundOutwards);

	// If this layer doesn't intersect with the larger sampledArea, skip capturing it
	Rect ignore;
	if (!transformed.intersect(sampledArea, &ignore)) return;

	// If the layer doesn't intersect a sampling area, skip capturing it
	bool intersectsAnyArea = false;
	for (const auto& [area, stopLayer, listener] : descriptors) {
	if (transformed.intersect(area, &ignore)) {
	intersectsAnyArea = true;
	listeners.insert(listener);
	}
	}
	if (!intersectsAnyArea) return;

	ALOGV("Traversing [%s] [%d, %d, %d, %d]", layer->getName().string(), bounds.left,
	bounds.top, bounds.right, bounds.bottom);
	visitor(layer);
	};
	mFlinger.traverseLayersInDisplay(device, filterVisitor);
	};

	sp<GraphicBuffer> buffer = nullptr;
	if (mCachedBuffer && mCachedBuffer->getWidth() == sampledArea.getWidth() &&
	mCachedBuffer->getHeight() == sampledArea.getHeight()) {
	buffer = mCachedBuffer;
	} else {
	const uint32_t usage = GRALLOC_USAGE_SW_READ_OFTEN \| GRALLOC_USAGE_HW_RENDER;
	buffer = new GraphicBuffer(sampledArea.getWidth(), sampledArea.getHeight(),
	PIXEL_FORMAT_RGBA_8888, 1, usage, "RegionSamplingThread");
	}

	bool ignored;
	mFlinger.captureScreenCommon(renderArea, traverseLayers, buffer, false, ignored);

	std::vector<Descriptor> activeDescriptors;
	for (const auto& descriptor : descriptors) {
	if (listeners.count(descriptor.listener) != 0) {
	activeDescriptors.emplace_back(descriptor);
	}
	}

	ALOGV("Sampling %zu descriptors", activeDescriptors.size());
	std::vector<float> lumas =
	sampleBuffer(buffer, sampledArea.leftTop(), activeDescriptors, orientation);
	if (lumas.size() != activeDescriptors.size()) {
	ALOGW("collected %zu median luma values for %zu descriptors", lumas.size(),
	activeDescriptors.size());
	return;
	}

	for (size_t d = 0; d < activeDescriptors.size(); ++d) {
	activeDescriptors[d].listener->onSampleCollected(lumas[d]);
	}

	// Extend the lifetime of mCachedBuffer from the previous frame to here to ensure that:
	// 1) The region sampling thread is the last owner of the buffer, and the freeing of the buffer
	// happens in this thread, as opposed to the main thread.
	// 2) The listener(s) receive their notifications prior to freeing the buffer.
	mCachedBuffer = buffer;
	ATRACE_INT(lumaSamplingStepTag, static_cast<int>(samplingStep::noWorkNeeded));
	}

	// NO_THREAD_SAFETY_ANALYSIS is because std::unique_lock presently lacks thread safety annotations.
	void RegionSamplingThread::threadMain() NO_THREAD_SAFETY_ANALYSIS {
	std::unique_lock<std::mutex> lock(mThreadControlMutex);
	while (mRunning) {
	if (mSampleRequested) {
	mSampleRequested = false;
	lock.unlock();
	captureSample();
	lock.lock();
	}
	mCondition.wait(lock, [this]() REQUIRES(mThreadControlMutex) {
	return mSampleRequested \|\| !mRunning;
	});
	}
	}

	} // namespace android