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Android下SF合成流程重学习之onMessageInvalidate

news 2025/12/26 13:48:47

Android下SF合成流程重学习之onMessageInvalidate

引言

虽然看了很多关于Android Graphics图形栈的文章和博客，但是都没有形成自己的知识点。每次学习了，仅仅是学习了而已，没有形成自己的知识体系，这次趁着有时间，这次必须把这个事情干透彻了！

本篇引用的代码，主要是Android R的。

并且Android下Graphics图形栈牵涉的点，太多了，这篇博客我们着重分析SF合成流程重学习之onMessageInvalidate的处理流程！

SurfaceFlinger layer之间的对应关系

先用一张图来看下各个部分之间layer的对应关系。接下来会根据这个图来解析是如何进行转换的,如下:

一. SF处理事务和处理Buffer

在SF的onMessageInvalidate主要是用来，处理事物和处理相关Buffer的，我们在下面的博客中详细分析！

在这里插入图片描述

1.1 onMessageInvalidate

文件： frameworks/native/services/surfaceflinger/Surfaceflinger.cppvoid SurfaceFlinger::onMessageInvalidate(nsecs_t expectedVSyncTime) {ATRACE_CALL();const nsecs_t frameStart = systemTime();// expectedVSyncTime 是vsync回调带过来的时间戳，通过nextAnticipatedVSyncTimeFrom 计算得到if (expectedVSyncTime >= frameStart) {mExpectedPresentTime = expectedVSyncTime;} else {mExpectedPresentTime = mScheduler->getDispSyncExpectedPresentTime(frameStart);}// 存储上一帧的expectedVSyncTimeconst nsecs_t lastScheduledPresentTime = mScheduledPresentTime;mScheduledPresentTime = expectedVSyncTime;...// 根据上一帧的present fence判断当前这一帧是否pendingconst TracedOrdinal<bool> framePending = {"PrevFramePending",previousFramePending(graceTimeForPresentFenceMs)};// 若framePending  或者 上一帧present fence释放的时间  > 上一帧vsync计算的时间戳 + vsync周期的一半// 则当前帧要丢掉DisplayStatInfo stats;mScheduler->getDisplayStatInfo(&stats);const nsecs_t frameMissedSlop = stats.vsyncPeriod / 2;const nsecs_t previousPresentTime = previousFramePresentTime();const TracedOrdinal<bool> frameMissed = {"PrevFrameMissed",framePending ||(previousPresentTime >= 0 &&(lastScheduledPresentTime <previousPresentTime - frameMissedSlop))};// 根据合成类型判断丢帧的类型const TracedOrdinal<bool> hwcFrameMissed = {"PrevHwcFrameMissed",mHadDeviceComposition && frameMissed};const TracedOrdinal<bool> gpuFrameMissed = {"PrevGpuFrameMissed",mHadClientComposition && frameMissed};...// 这部分涉及帧率切换，先是通过performSetActiveConfig 将新的帧率给到hwc，然后下一帧再更新sf这边的状态if (mSetActiveConfigPending) {if (framePending) {mEventQueue->invalidate();return;}// We received the present fence from the HWC, so we assume it successfully updated// the config, hence we update SF.mSetActiveConfigPending = false;ON_MAIN_THREAD(setActiveConfigInternal());}
}//  mPropagateBackpressure 可以通过adb shell setprop debug.sf.disable_backpressure x 来控制,表示系统是否允许丢帧//  若允许丢帧则skip这次刷帧if (framePending && mPropagateBackpressure) {if ((hwcFrameMissed && !gpuFrameMissed) || mPropagateBackpressureClientComposition) {signalLayerUpdate();return;}}....bool refreshNeeded;{ConditionalLockGuard<std::mutex> lock(mTracingLock, mTracingEnabled);// 主要的逻辑在这两个函数，简单理解为处理layer或者display的事务和layer的bufferrefreshNeeded = handleMessageTransaction();refreshNeeded |= handleMessageInvalidate();...}// 帧率切换，SurfaceFlinger主线程执行ON_MAIN_THREAD(performSetActiveConfig());...// 若layer的事务有变化或者有新的buffer，则触发refreshsignalRefresh();
}

上述onMessageInvalidate概括来说，其主要处理的事情如下:

判断当前帧是否丢掉
handleMessageTransaction 处理layer或者display事务
handleMessageInvalidate 处理应用queue过来的Buffer
帧率切换
触发刷新流程

1.2 handleMessageTransaction

文件： frameworks/native/services/surfaceflinger/Surfaceflinger.cppbool SurfaceFlinger::handleMessageTransaction() {ATRACE_CALL();// 获取当前的mTransactionFlags，mTransactionFlags 由setTransactionFlags 赋值，比如CreateLayer时会给mTransactionFlags 赋值eTransactionNeeded// createDisplay 时会给mTransactionFlags 赋值 eDisplayTransactionNeededuint32_t transactionFlags = peekTransactionFlags();// flushTransactionQueues 会消费transactionQueue，transactionQueue 是上层通过SurfaceComposerClient 设的，然后再通过binder设置给sf这边// setDisplayStateLocked： 处理display的事务// setClientStateLocked： 处理layer的事务// 这两部分事务都存放在surfaceflinger的mCurrentState 里面bool flushedATransaction = flushTransactionQueues();// 有新的事务则要执行handleTransactionbool runHandleTransaction =(transactionFlags && (transactionFlags != eTransactionFlushNeeded)) ||flushedATransaction ||mForceTraversal;// 处理layer和display的事务if (runHandleTransaction) {handleTransaction(eTransactionMask);} else {getTransactionFlags(eTransactionFlushNeeded);}if (transactionFlushNeeded()) {setTransactionFlags(eTransactionFlushNeeded);}return runHandleTransaction;
}//来看下display和layer有哪些事务处理文件： frameworks/native/services/surfaceflinger/Surfaceflinger.cpp// display的事务，包括display Surface, layerStack , Projection , viewport, Size发生变化时附上eDisplayTransactionNeeded 这个flags
uint32_t SurfaceFlinger::setDisplayStateLocked(const DisplayState& s) {const ssize_t index = mCurrentState.displays.indexOfKey(s.token);if (index < 0) return 0;uint32_t flags = 0;DisplayDeviceState& state = mCurrentState.displays.editValueAt(index);const uint32_t what = s.what;if (what & DisplayState::eSurfaceChanged) {if (IInterface::asBinder(state.surface) != IInterface::asBinder(s.surface)) {state.surface = s.surface;flags |= eDisplayTransactionNeeded;}}if (what & DisplayState::eLayerStackChanged) {if (state.layerStack != s.layerStack) {state.layerStack = s.layerStack;flags |= eDisplayTransactionNeeded;}}if (what & DisplayState::eDisplayProjectionChanged) {if (state.orientation != s.orientation) {state.orientation = s.orientation;flags |= eDisplayTransactionNeeded;}if (state.frame != s.frame) {state.frame = s.frame;flags |= eDisplayTransactionNeeded;}if (state.viewport != s.viewport) {state.viewport = s.viewport;flags |= eDisplayTransactionNeeded;}}if (what & DisplayState::eDisplaySizeChanged) {if (state.width != s.width) {state.width = s.width;flags |= eDisplayTransactionNeeded;}if (state.height != s.height) {state.height = s.height;flags |= eDisplayTransactionNeeded;}}return flags;
}文件： frameworks/native/services/surfaceflinger/Surfaceflinger.cpp// layer的事务，包括ePositionChanged, eLayerChanged, eAlphaChanged 等等，跟上层的surface设置一样，同样的事务同步给layer
uint32_t SurfaceFlinger::setClientStateLocked(const ComposerState& composerState, int64_t desiredPresentTime, int64_t postTime,bool privileged,std::unordered_set<ListenerCallbacks, ListenerCallbacksHash>& listenerCallbacks) {
...  sp<Layer> layer = nullptr;if (s.surface) {layer = fromHandleLocked(s.surface).promote();...if (what & layer_state_t::eDeferTransaction_legacy) {layer->pushPendingState();}// Only set by BLAST adapter layersif (what & layer_state_t::eProducerDisconnect) {layer->onDisconnect();}if (what & layer_state_t::ePositionChanged) {if (layer->setPosition(s.x, s.y)) {flags |= eTraversalNeeded;}}
...
}

通过setDisplayStateLocked 和 setClientStateLocked 获取了display和layer的事务变化的flag，并且setClientStateLocked还将layer与surface进行了事务的同步。

文件：  frameworks/native/services/surfaceflinger/Surfaceflinger.cppvoid SurfaceFlinger::handleTransactionLocked(uint32_t transactionFlags)
{...if ((transactionFlags & eTraversalNeeded) || mForceTraversal) {mForceTraversal = false;// 遍历mCurrentState 里面的layer，对有事务变化的layer进行处理，doTransaction 主要的处理逻辑是对sync ponit的处理，// sync ponit用于延迟显示的一些layer，根据FrameNumber进行同步，如果当前帧数达到了设定值，latchBuffer就可以消费这个layermCurrentState.traverse([&](Layer* layer) {uint32_t trFlags = layer->getTransactionFlags(eTransactionNeeded);if (!trFlags) return;const uint32_t flags = layer->doTransaction(0);if (flags & Layer::eVisibleRegion)mVisibleRegionsDirty = true;if (flags & Layer::eInputInfoChanged) {mInputInfoChanged = true;}});}// 处理 display的 事务逻辑if (transactionFlags & eDisplayTransactionNeeded) {processDisplayChangesLocked();processDisplayHotplugEventsLocked();}...// SurfaceFlinger维持mCurrentState 和 mDrawingState 两个状态，是个大的结构体，mCurrentState 可以理解为下一帧的// layer和display的状态， mDrawingState 可以理解为当前帧的状态，commitTransaction 将 mCurrentState 更新到这一帧的状态commitTransaction();
}

handleMessageTransaction主要的作用是处理display和layer的事物，将上层的surface和底层的layer属性做个同步，涉及到很多的细节以后遇到具体场景来分析，最后将mCurrentState 赋给 mDrawingState 更新到当前这一帧的状态。

1.3 handleMessageInvalidate

我们接着继续往下看，累啊，学习，搞起来~

文件：frameworks/native/services/surfaceflinger/Surfaceflinger.cppbool SurfaceFlinger::handleMessageInvalidate() {ATRACE_CALL();// 处理queue过来的Bufferbool refreshNeeded = handlePageFlip();if (mVisibleRegionsDirty) {// 如果可见区域有变化，则重新计算layer的范围computeLayerBounds();}//判断需要刷新的layer是否属于当前Outputfor (auto& layer : mLayersPendingRefresh) {Region visibleReg;visibleReg.set(layer->getScreenBounds());invalidateLayerStack(layer, visibleReg);}mLayersPendingRefresh.clear();return refreshNeeded;
}bool SurfaceFlinger::handlePageFlip()
{...// 遍历 mDrawingState里面的layer，判断该layer是否可在当前vsync内显示，如果queueBuffer带过来的时间戳大于Vsync的时间戳，则表示该layer不能在当前vsync内显示// 能够显示的layer放到mLayersWithQueuedFrames 里面mDrawingState.traverse([&](Layer* layer) {if (layer->hasReadyFrame()) {frameQueued = true;if (layer->shouldPresentNow(expectedPresentTime)) {mLayersWithQueuedFrames.push_back(layer);} else {ATRACE_NAME("!layer->shouldPresentNow()");layer->useEmptyDamage();}} else {layer->useEmptyDamage();}});...// 遍历mLayersWithQueuedFrames 里面的layer，执行latchBuffer，在latchBuffer里面消费Buffer// 成功消费的layer放到mLayersPendingRefresh 里面for (auto& layer : mLayersWithQueuedFrames) {if (layer->latchBuffer(visibleRegions, latchTime, expectedPresentTime)) {mLayersPendingRefresh.push_back(layer);}layer->useSurfaceDamage();if (layer->isBufferLatched()) {newDataLatched = true;}...// 当有需要消费Buffer的layer则返回truereturn !mLayersWithQueuedFrames.empty() && newDataLatched;文件： frameworks/native/services/surfaceflinger/BufferLayer.cppbool BufferLayer::latchBuffer(bool& recomputeVisibleRegions, nsecs_t latchTime,nsecs_t expectedPresentTime) {...// 执行顺序BufferQueueLayer-> updateTexImage ==> BufferLayerConsumer-> updateTexImage,具体逻辑在// BufferLayerConsumer 里面status_t err = updateTexImage(recomputeVisibleRegions, latchTime, expectedPresentTime);// 更新mBufferInfo里的buffer，这个变量是在BufferQueueLayer里面维护err = updateActiveBuffer();if (err != NO_ERROR) {return false;}//更新mBufferInfo的FrameNumbererr = updateFrameNumber(latchTime);if (err != NO_ERROR) {return false;}// 更新到mBufferInfogatherBufferInfo();...
}文件： frameworks/native/services/surfaceflinger/BufferLayerConsumer.cppstatus_t BufferLayerConsumer::updateTexImage(BufferRejecter* rejecter, nsecs_t expectedPresentTime,bool* autoRefresh, bool* queuedBuffer,uint64_t maxFrameNumber) {...BufferItem item;// acquireBuffer：消费queue过来的Buffer,放到item里面status_t err = acquireBufferLocked(&item, expectedPresentTime, maxFrameNumber);...// 更新BufferLayerConsumer 状态，都是从queueBuffer设置而来err = updateAndReleaseLocked(item, &mPendingRelease);...
}status_t BufferLayerConsumer::acquireBufferLocked(BufferItem* item, nsecs_t presentWhen,uint64_t maxFrameNumber) {status_t err = ConsumerBase::acquireBufferLocked(item, presentWhen, maxFrameNumber);...if (item->mGraphicBuffer != nullptr) {std::lock_guard<std::mutex> lock(mImagesMutex);if (mImages[item->mSlot] == nullptr || mImages[item->mSlot]->graphicBuffer() == nullptr ||mImages[item->mSlot]->graphicBuffer()->getId() != item->mGraphicBuffer->getId()) {// 将acquire出来的Buffer做成EGLImage，为了后面GPU合成mImages[item->mSlot] = std::make_shared<Image>(item->mGraphicBuffer, mRE);}}return NO_ERROR;
}文件： frameworks/native/libs/gui/ConsumerBase.cppstatus_t ConsumerBase::acquireBufferLocked(BufferItem *item,nsecs_t presentWhen, uint64_t maxFrameNumber) {...// 实现在BufferQueueConsumer的 acquireBufferstatus_t err = mConsumer->acquireBuffer(item, presentWhen, maxFrameNumber);if (err != NO_ERROR) {return err;}if (item->mGraphicBuffer != nullptr) {if (mSlots[item->mSlot].mGraphicBuffer != nullptr) {freeBufferLocked(item->mSlot);}//更新Bufferslot里面的GraphicsBuffer，这个Buffer的owner是GPU在处理mSlots[item->mSlot].mGraphicBuffer = item->mGraphicBuffer;}// 更新Bufferslot里面的frameNumber和fence，与queueBuffer设置保持一致，这里的fence为acquireFencemSlots[item->mSlot].mFrameNumber = item->mFrameNumber;mSlots[item->mSlot].mFence = item->mFence;CB_LOGV("acquireBufferLocked: -> slot=%d/%" PRIu64,item->mSlot, item->mFrameNumber);return OK;
}文件： frameworks/native/libs/gui/BufferQueueConsumer.cpp//跳过一些特殊情况代码细节，把主线code拎出来分析
status_t BufferQueueConsumer::acquireBuffer(BufferItem* outBuffer,nsecs_t expectedPresent, uint64_t maxFrameNumber) {...// queueBuffer时入的队列BufferQueueCore::Fifo::iterator front(mCore->mQueue.begin());...// 拿到queueBuffer对应的slot和BufferItemslot = front->mSlot;*outBuffer = *front;...if (!outBuffer->mIsStale) {mSlots[slot].mAcquireCalled = true;// Don't decrease the queue count if the BufferItem wasn't// previously in the queue. This happens in shared buffer mode when// the queue is empty and the BufferItem is created above.if (mCore->mQueue.empty()) {mSlots[slot].mBufferState.acquireNotInQueue();} else {// 更新状态为acquiremSlots[slot].mBufferState.acquire();}// queueBuffer入队，acquireBuffer出队mCore->mQueue.erase(front);...
}

handleMessageInvalidate主要作用是执行 latchBuffer 去 acquire 应用queue过来的Buffer，然后拿到queueBuffer时设的Bufferslot一些状态属性给到BufferQueueLayer的mBufferInfo，同时还把这个Buffer做成EGLImage为后面的GPU合成做准备，期间都是数据之间的传递，所以说SurfaceFlinger并未真正触碰Buffer的内容。

写在最后

好了今天的博客Android下SF合成流程重学习之onMessageInvalidate就到这里了。总之，青山不改绿水长流先到这里了。如果本博客对你有所帮助，麻烦关注或者点个赞，如果觉得很烂也可以踩一脚！谢谢各位了！！

Android下SF合成流程重学习之onMessageInvalidate