Surface在C++层的创建源码解析
源码为：android4.4.4
1、创建SurfaceComposerClient绘图客户端
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// create a client to surfaceflinger sp<SurfaceComposerClient> client = new SurfaceComposerClient(); //创建SurfaceFlinger的本地代理 |
展开SurfaceComposerClient源码：frameworks\native\libs\gui\SurfaceComposerClient.cpp
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SurfaceComposerClient::SurfaceComposerClient() : mStatus(NO_INIT), mComposer(Composer::getInstance()) // Composer::getInstance() 应该是一个单例模式 { } |
mStatus： 为status_t类型变量 ， mComposer：为Composer&的引用
Composer类为SurfaceComposerClient类的友元类。
Composer::getInstance()获取一个Composer对象赋值给mComposer。
现在client对象的两个变量mStatus和mComposer都有值了。
2、通过client对象获取屏幕信息
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DisplayInfo display; //获取屏幕的宽高等信息 client->getDisplayInfo(client->getBuiltInDisplay(HWC_DISPLAY_PRIMARY), &display); |
将获取到的屏幕信息存放发哦display这个结构体里。
看看client->getBuiltInDisplay(HWC_DISPLAY_PRIMARY)这个是什么意思。
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sp<IBinder> SurfaceComposerClient::getBuiltInDisplay(int32_t id) { return Composer::getInstance().getBuiltInDisplay(id); } //调用Composer的getBuiltInDisplay方法 |
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sp<IBinder> Composer::getBuiltInDisplay(int32_t id) { return ComposerService::getComposerService()->getBuiltInDisplay(id); }//再次调用ComposerService对象的getBuiltInDisplay方法 |
client-> getBuiltInDisplay最终获取到一个Ibinder对象
再看看client->getDisplayInfo这个方法
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status_t SurfaceComposerClient::getDisplayInfo( const sp<IBinder>& display, DisplayInfo* info) { return ComposerService::getComposerService()->getDisplayInfo(display, info); } |
根据HWC_DISPLAY_PRIMARY获取Ibinder对象，根据Binder对象获取ComposerSeveice对象调用取得屏幕信息。
3、根据SurfaceComposerClient对象创建SurfafeControl对象
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//创建SurfaceControl的本地代理 sp<SurfaceControl> surfaceControl = client->createSurface(String8("testsurface"), display.w, display.h, PIXEL_FORMAT_RGBA_8888, 0); |
看看createSurface源码
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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); //通知服务端申请surface ALOGE_IF(err, "SurfaceComposerClient::createSurface error %s", strerror(-err)); if (err == NO_ERROR) { sur = new SurfaceControl(this, handle, gbp); //如果申请成功就创建 } } return sur; } |
mClient是什么东西：sp<ISurfaceComposerClient> mClient; IsurfaceComposerClient是Binder的一个接口类。
先申请surface申请成功就创建一个surfaceControl的本地代理。
4、设置surface的图层Z轴
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SurfaceComposerClient::openGlobalTransaction(); surfaceControl->setLayer(120000); //设置z轴 surfaceControl->setSize(display.w, display.h); surfaceControl->setPosition(0, 0); //起始位置 SurfaceComposerClient::closeGlobalTransaction(); //默认false |
SurfaceComposerClient::openGlobalTransaction() 源码展开后：
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void SurfaceComposerClient::openGlobalTransaction() { Composer::openGlobalTransaction(); } |
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static void openGlobalTransaction() { Composer::getInstance().openGlobalTransactionImpl(); } |
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void Composer::openGlobalTransactionImpl() { { // scope for the lock Mutex::Autolock _l(mLock); mTransactionNestCount += 1; //最终是给这个变量加1 } } |
看看surfaceControl->setLayer(120000)设置z轴展开：
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status_t SurfaceComposerClient::setLayer(const sp<IBinder>& id, int32_t z) { return getComposer().setLayer(this, id, z); } |
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status_t Composer::setLayer(const sp<SurfaceComposerClient>& client, const sp<IBinder>& id, int32_t z) { Mutex::Autolock _l(mLock); layer_state_t* s = getLayerStateLocked(client, id);//状态加锁 if (!s) return BAD_INDEX; s->what |= layer_state_t::eLayerChanged; s->z = z; return NO_ERROR; } |
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layer_state_t* Composer::getLayerStateLocked( const sp<SurfaceComposerClient>& client, const sp<IBinder>& id) { ComposerState s; s.client = client->mClient; s.state.surface = id; //将设置的Z轴坐标存在ComposerState对象里 ssize_t index = mComposerStates.indexOf(s); //查看链表中是否有该坐标 if (index < 0) { //没有就添加 // we don't have it, add an initialized layer_state to our list index = mComposerStates.add(s); //将这个ComposerState对象存放到链表中 } ComposerState* const out = mComposerStates.editArray(); return &(out[index].state); } |
以上就是设置Z轴方法，调用Composer对象getLayerStateLocked进行加锁，创建一个ComposerState对象，将传递进来的值存进行检查，检查是否存在，如果不存在就直接储到mComposerStates链表中。
SurfaceComposerClient::closeGlobalTransaction()展开：
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void SurfaceComposerClient::closeGlobalTransaction(bool synchronous) { Composer::closeGlobalTransaction(synchronous); } |
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static void closeGlobalTransaction(bool synchronous) { Composer::getInstance().closeGlobalTransactionImpl(synchronous); } |
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void Composer::closeGlobalTransactionImpl(bool synchronous) { sp<ISurfaceComposer> sm(ComposerService::getComposerService()); Vector<ComposerState> transaction; Vector<DisplayState> displayTransaction; uint32_t flags = 0; { // scope for the lock Mutex::Autolock _l(mLock); mForceSynchronous |= synchronous; if (!mTransactionNestCount) { ALOGW("At least one call to closeGlobalTransaction() was not matched by a prior " "call to openGlobalTransaction()."); } else if (--mTransactionNestCount) { //和锁定时正好相反 return; 直接退出 } //后面是没有进行上面的锁定，才执行下面该部分 transaction = mComposerStates; mComposerStates.clear(); displayTransaction = mDisplayStates; mDisplayStates.clear(); if (mForceSynchronous) { flags |= ISurfaceComposer::eSynchronous; } if (mAnimation) { flags |= ISurfaceComposer::eAnimation; } mForceSynchronous = false; mAnimation = false; } sm->setTransactionState(transaction, displayTransaction, flags); } |
5、获取surface
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// 获取Surface本地代理 sp<Surface> surface = surfaceControl->getSurface();//获取surface |
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sp<Surface> SurfaceControl::getSurface() const { Mutex::Autolock _l(mLock); if (mSurfaceData == 0) { // This surface is always consumed by SurfaceFlinger, so the // producerControlledByApp value doesn't matter; using false. mSurfaceData = new Surface(mGraphicBufferProducer, false); } return mSurfaceData; } |
直接new一个suface对象返回
6、surface->lock() 和surface->unlockAndPost();
Lock从屏幕缓冲队列中申请屏幕，再使用unlockAndpost将申请的屏幕加入到缓冲队列中交给surfaceflinger进行组合并显示在屏幕上。其实这才是绘图显示最重要的阶段，绘图显示快慢和这里优化有直接关系。