前情提要
SurfaceFlinger 的架構十分龐大且複雜, 新手進入不易我們先從 BootAnimation 的實例分析來對 SurfaceFlinger 進行初步的了解 (｢･ω･)｢
bootanimation 做為一個可執行檔, 是在 init.rc 裡作為一個 service 帶起來的:
service bootanim /system/bin/bootanimation
查看bootanimation_main.cpp, 你可以發現它會察看一個 property (debug.sf.nobootanimation)來決定是否要執行 boot animation.
如果需要執行的話, 它會生成一個 BootAnimation 物件, 這就是真正運行起開機動畫的 class 了.
那麼, 我們首先從建構子開始下手!
BootAnimation::BootAnimation() : Thread(false), mZip(NULL) { mSession = new SurfaceComposerClient(); } void BootAnimation::onFirstRef() { status_t err = mSession->linkToComposerDeath(this); ALOGE_IF(err, "linkToComposerDeath failed (%s) ", strerror(-err)); if (err == NO_ERROR) { run("BootAnimation", PRIORITY_DISPLAY); } }
一開始生成了一個 SurfaceComposeClient 對象, 名為 mSession
可以想見的是要跟 SurfaceFlinger 溝通就是透過這個 mSession 來負責
我們看一下 SurfaceComposeClient 的建構子:
SurfaceComposerClient::SurfaceComposerClient() : mStatus(NO_INIT), mComposer(Composer::getInstance()) { } void SurfaceComposerClient::onFirstRef() { sp<ISurfaceComposer> sm(ComposerService::getComposerService()); if (sm != 0) { sp<ISurfaceComposerClient> conn = sm->createConnection(); if (conn != 0) { mClient = conn; mStatus = NO_ERROR; } } }
這邊可以看到 Composer 跟 ComposerService 都是一個 singleton 的模式
雖然大家透過不同的 SurfaceComoserClient 來跟 SurfaceFlinger 溝通, 但是一次只有一個人可以使用服務
mComposer
這裡的 mComposer 並不是真正意義上去負責做 Compose 的那個 Composer, 而是比較接近讓 SurfaceComoserClient 有了一個上鎖的機制, 並且跟 ComposerService 來溝通
sm(ComposerService::getComposerSerivce())
這個 getComposerService() 會去取得 SurfaceFlinger 這個 service
(又一個前情提要, SurfaceFlinger 的服務是由 main_surfaceflinger.cpp 加入的, 它也是從 init.rc 帶起來的一個 service)
這裡呼叫了 sm->createConnection(),
在 SurfaceFlinger中會創建一個 ISurfaceComposerClient 對象回來, 並記為 mClient
sp<ISurfaceComposerClient> SurfaceFlinger::createConnection() { sp<ISurfaceComposerClient> bclient; sp<Client> client(new Client(this)); status_t err = client->initCheck(); if (err == NO_ERROR) { bclient = client; } return bclient; }
簡單的初始化結束後, 目前 BootAnimation 已經透過了 SurfaceComposerClient 與 SurfaceFlinger 建立起關係
接下來回到 BootAnimation
因為 onFirstRef 呼叫了 run(), 所以這邊會依序執行 readyToRun() 跟 threadLoop()
status_t BootAnimation::readyToRun() { // create the native surface sp<SurfaceControl> control = session()->createSurface(String8("BootAnimation"), dinfo.w, dinfo.h, PIXEL_FORMAT_RGB_565); ... }
首先透過 SurfaceComposerClient 呼叫 createSurface, 並帶入了 Display 的寬高資訊
在這裡一定就是透過 mClient 對象去呼叫 SurfaceFlinger,
不過可以注意到這邊出現了一些新人物, 分別是:
handle, gbp, 以及 SurfaceControl
sp<SurfaceControl> SurfaceComposerClient::createSurface( const String8& name, uint32_t w, uint32_t h, PixelFormat format, uint32_t flags) { sp<SurfaceControl> sur; if (mStatus == NO_ERROR) { sp<IBinder> handle; sp<IGraphicBufferProducer> gbp; status_t err = mClient->createSurface(name, w, h, format, flags, &handle, &gbp); ALOGE_IF(err, "SurfaceComposerClient::createSurface error %s", strerror(-err)); if (err == NO_ERROR) { sur = new SurfaceControl(this, handle, gbp); } } return sur; }
先記得有這幾位新人, 我們看一下 createSurface 做了甚麼
status_t Client::createSurface( const String8& name, uint32_t w, uint32_t h, PixelFormat format, uint32_t flags, sp<IBinder>* handle, sp<IGraphicBufferProducer>* gbp) { /* * createSurface must be called from the GL thread so that it can * have access to the GL context. */ // 定義一個 Message +++ class MessageCreateLayer : public MessageBase { SurfaceFlinger* flinger; Client* client; sp<IBinder>* handle; sp<IGraphicBufferProducer>* gbp; status_t result; const String8& name; uint32_t w, h; PixelFormat format; uint32_t flags; public: MessageCreateLayer(SurfaceFlinger* flinger, const String8& name, Client* client, uint32_t w, uint32_t h, PixelFormat format, uint32_t flags, sp<IBinder>* handle, sp<IGraphicBufferProducer>* gbp) : flinger(flinger), client(client), handle(handle), gbp(gbp), name(name), w(w), h(h), format(format), flags(flags) { } status_t getResult() const { return result; } virtual bool handler() { result = flinger->createLayer(name, client, w, h, format, flags, handle, gbp); return true; } }; // 定義一個 Message --- // 生成 Message sp<MessageBase> msg = new MessageCreateLayer(mFlinger.get(), name, this, w, h, format, flags, handle, gbp); // 將 Message 放入 Queue, 並等待回傳 mFlinger->postMessageSync(msg); return static_cast<MessageCreateLayer*>( msg.get() )->getResult(); }
這是在 SurfaceFlinger 裡面一個很經典的呼叫, 這整段可以分成
1.) 定義一個 Message, 他用來呼叫 CreateLayer, 所以是 MessageCreateLayer
2.) 生成這個 Message, 並丟入 MessageQueue 中
3.) 等待 Message 處理完 (postMessageSync), 並回傳處理完的 Result
從這個 Message 的定義來看, 你會發現輪到處理它時, 就是執行這個 Message 的 handler
在這裡就是 SurfaceFlinger::createLayer();
各位的 SAN 值, 現在感覺如何呀?
(」・ω・)」SAN値！(／・ω・)／ピンチ！
初次看這段的同學應該會覺得東西怎麼又多又亂,
我的建議是先大略看過一次了解每個部件的關鍵是甚麼, 再回頭熟讀.
那麼, 下面繼續展開 createLayer:
status_t SurfaceFlinger::createLayer( const String8& name, const sp<Client>& client, uint32_t w, uint32_t h, PixelFormat format, uint32_t flags, sp<IBinder>* handle, sp<IGraphicBufferProducer>* gbp) { status_t result = NO_ERROR; sp<Layer> layer;
switch (flags & ISurfaceComposerClient::eFXSurfaceMask) { case ISurfaceComposerClient::eFXSurfaceNormal: result = createNormalLayer(client, name, w, h, flags, format, handle, gbp, &layer); break; case ISurfaceComposerClient::eFXSurfaceDim: result = createDimLayer(client, name, w, h, flags, handle, gbp, &layer); break; default: result = BAD_VALUE; break; } result = addClientLayer(client, *handle, *gbp, layer); setTransactionFlags(eTransactionNeeded); return result; }
這裡因為預設的 flags 是 0, 所以會走 createNormalLayer
status_t SurfaceFlinger::createNormalLayer(const sp<Client>& client, const String8& name, uint32_t w, uint32_t h, uint32_t flags, PixelFormat& format, sp<IBinder>* handle, sp<IGraphicBufferProducer>* gbp, sp<Layer>* outLayer) { // initialize the surfaces switch (format) { case PIXEL_FORMAT_TRANSPARENT: case PIXEL_FORMAT_TRANSLUCENT: format = PIXEL_FORMAT_RGBA_8888; break; case PIXEL_FORMAT_OPAQUE: format = PIXEL_FORMAT_RGBX_8888; break; } *outLayer = new Layer(this, client, name, w, h, flags); status_t err = (*outLayer)->setBuffers(w, h, format, flags); if (err == NO_ERROR) { *handle = (*outLayer)->getHandle(); *gbp = (*outLayer)->getProducer(); } ALOGE_IF(err, "createNormalLayer() failed (%s)", strerror(-err)); return err; }
前面的format不會影響 (我們帶入的是 PIXEL_FORMAT_RGB_565)
因此這邊就是再生成了一個 Layer 對象, 並且把前面的 handle 跟 gbp 也一併賦址了
見到老朋友的感覺真好 (ﾉ∀`*)
讓我們看看 Layer 的建構子吧:
Layer::Layer(SurfaceFlinger* flinger, const sp<Client>& client, const String8& name, uint32_t w, uint32_t h, uint32_t flags) : contentDirty(false), sequence(uint32_t(android_atomic_inc(&sSequence))), mFlinger(flinger), mTextureName(-1U), mPremultipliedAlpha(true), mName("unnamed"), mFormat(PIXEL_FORMAT_NONE), mTransactionFlags(0), mQueuedFrames(0), mSidebandStreamChanged(false), mCurrentTransform(0), mCurrentScalingMode(NATIVE_WINDOW_SCALING_MODE_FREEZE), mCurrentOpacity(true), mRefreshPending(false), mFrameLatencyNeeded(false), mFiltering(false), mNeedsFiltering(false), mMesh(Mesh::TRIANGLE_FAN, 4, 2, 2), mProtectedByApp(false), mHasSurface(false), mClientRef(client), mPotentialCursor(false), mQueueItemLock(), mQueueItemCondition(), mQueueItems(), mLastFrameNumberReceived(0), mUpdateTexImageFailed(false) { mCurrentCrop.makeInvalid(); mFlinger->getRenderEngine().genTextures(1, &mTextureName); mTexture.init(Texture::TEXTURE_EXTERNAL, mTextureName); uint32_t layerFlags = 0; if (flags & ISurfaceComposerClient::eHidden) layerFlags |= layer_state_t::eLayerHidden; if (flags & ISurfaceComposerClient::eOpaque) layerFlags |= layer_state_t::eLayerOpaque; if (flags & ISurfaceComposerClient::eSecure) layerFlags |= layer_state_t::eLayerSecure; if (flags & ISurfaceComposerClient::eNonPremultiplied) mPremultipliedAlpha = false; mName = name; mCurrentState.active.w = w; mCurrentState.active.h = h; mCurrentState.active.crop.makeInvalid(); mCurrentState.z = 0; mCurrentState.alpha = 0xFF; mCurrentState.layerStack = 0; mCurrentState.flags = layerFlags; mCurrentState.sequence = 0; mCurrentState.transform.set(0, 0); mCurrentState.requested = mCurrentState.active; // drawing state & current state are identical mDrawingState = mCurrentState; nsecs_t displayPeriod = flinger->getHwComposer().getRefreshPeriod(HWC_DISPLAY_PRIMARY); mFrameTracker.setDisplayRefreshPeriod(displayPeriod); }
好在我們甚麼 flags 都沒有帶進來呢~
這邊看起來比較重要的人是 mDrawingState, 不過現在還不知道它能做甚麼
這種時候呢...
(ㆆᴗㆆ)
就是先不管它
姑且先看一下 onFirstRef 做了甚麼
void Layer::onFirstRef() { // Creates a custom BufferQueue for SurfaceFlingerConsumer to use sp<IGraphicBufferProducer> producer; sp<IGraphicBufferConsumer> consumer; BufferQueue::createBufferQueue(&producer, &consumer); mProducer = new MonitoredProducer(producer, mFlinger); mSurfaceFlingerConsumer = new SurfaceFlingerConsumer(consumer, mTextureName); mSurfaceFlingerConsumer->setConsumerUsageBits(getEffectiveUsage(0)); mSurfaceFlingerConsumer->setContentsChangedListener(this); mSurfaceFlingerConsumer->setName(mName); mSurfaceFlingerConsumer->setDefaultMaxBufferCount(3); const sp<const DisplayDevice> hw(mFlinger->getDefaultDisplayDevice()); updateTransformHint(hw); }
野生的 BOSS 出現啦 (((ﾟДﾟ;)))
這個 Producer 跟 Consumer 非常重要, 我建議各位在這裡先存個檔
然後播放激昂的戰鬥配樂 (像是Granblue Fantasy マグナ戦 BGM)
我們, 下一篇見!
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