ViewRoot中surface的创建

阳光穿透心脏的1/2处 2022-05-22 10:29 130阅读 0赞

`ViewRootImpl`的`mSurface`变量指向`Surface`对象，这个surface对象是硬件渲染UI时`OpenGL`所使用的`ANativeWindow`，本文记录了这个surface时如何创建的。

ViewRoot，WMS，SurfaceFlinger三者的binder连接。

![Image 1][]

Surface.png

ViewRootImpl构造时会创建到wms的连接:

public ViewRootImpl(Context context, Display display) { mContext = context; mWindowSession = WindowManagerGlobal.getWindowSession();

ViewRootImpl.setView里会跨进程调用wms的addwindow将当前窗口添加到wms中:

res = mWindowSession.addToDisplay(mWindow, mSeq, mWindowAttributes, getHostVisibility(), mDisplay.getDisplayId(), mAttachInfo.mContentInsets, mAttachInfo.mStableInsets, mAttachInfo.mOutsets, mInputChannel); @Override public int addToDisplay(IWindow window, int seq, WindowManager.LayoutParams attrs, int viewVisibility, int displayId, Rect outContentInsets, Rect outStableInsets, Rect outOutsets, InputChannel outInputChannel) { return mService.addWindow(this, window, seq, attrs, viewVisibility, displayId, outContentInsets, outStableInsets, outOutsets, outInputChannel); }

wms.addWindow中创建WindowState，WindowState包装了client的跨进程回调接口，用来通知ViewRootIml一些消息。

WindowState win = new WindowState(this, session, client, token, attachedWindow, appOp[0], seq, attrs, viewVisibility, displayContent); ...... win.attach();

`WindowState.attach`

void attach() { if (WindowManagerService.localLOGV) Slog.v( TAG, "Attaching " + this + " token=" + mToken + ", list=" + mToken.windows); mSession.windowAddedLocked(); }

Session.windowAddedLocked中创建了SurfaceSession

void windowAddedLocked() { if (mSurfaceSession == null) { if (WindowManagerService.localLOGV) Slog.v( TAG_WM, "First window added to " + this + ", creating SurfaceSession"); mSurfaceSession = new SurfaceSession(); if (SHOW_TRANSACTIONS) Slog.i( TAG_WM, " NEW SURFACE SESSION " + mSurfaceSession); mService.mSessions.add(this); if (mLastReportedAnimatorScale != mService.getCurrentAnimatorScale()) { mService.dispatchNewAnimatorScaleLocked(this); } } mNumWindow++; }

SurfaceSession的构造函数中调用native方法nativeCreate中连接`SurfaceFlinger`创建`SurfaceComposerClient`，SurfaceFlinger中对应的BnBinder是Client。

public SurfaceSession() { mNativeClient = nativeCreate(); }

连接是建立好了，接下来就要创建surface了

ViewRootImpl.relayoutWindow中调用windowSession的relayout。将mSurface传入函数作为outSurface。

private int relayoutWindow(WindowManager.LayoutParams params, int viewVisibility, boolean insetsPending) throws RemoteException { ...... int relayoutResult = mWindowSession.relayout( mWindow, mSeq, params, (int) (mView.getMeasuredWidth() * appScale + 0.5f), (int) (mView.getMeasuredHeight() * appScale + 0.5f), viewVisibility, insetsPending ? WindowManagerGlobal.RELAYOUT_INSETS_PENDING : 0, mWinFrame, mPendingOverscanInsets, mPendingContentInsets, mPendingVisibleInsets, mPendingStableInsets, mPendingOutsets, mPendingBackDropFrame, mPendingConfiguration, mSurface);

wms的`relayout`会调用

result = createSurfaceControl(outSurface, result, win, winAnimator); private int createSurfaceControl(Surface outSurface, int result, WindowState win, WindowStateAnimator winAnimator) { if (!win.mHasSurface) { result |= RELAYOUT_RES_SURFACE_CHANGED; } WindowSurfaceController surfaceController = winAnimator.createSurfaceLocked(); if (surfaceController != null) { surfaceController.getSurface(outSurface); if (SHOW_TRANSACTIONS) Slog.i(TAG_WM, " OUT SURFACE " + outSurface + ": copied"); } else { // For some reason there isn't a surface. Clear the // caller's object so they see the same state. outSurface.release(); } return result; }

`WindowStateAnimator.createSurfaceLocked()`

mSurfaceController = new WindowSurfaceController(mSession.mSurfaceSession, attrs.getTitle().toString(), width, height, format, flags, this); public WindowSurfaceController(SurfaceSession s, String name, int w, int h, int format, int flags, WindowStateAnimator animator) { mAnimator = animator; mSurfaceW = w; mSurfaceH = h; title = name; // For opaque child windows placed under parent windows, // we use a special SurfaceControl which mirrors commands // to a black-out layer placed one Z-layer below the surface. // This prevents holes to whatever app/wallpaper is underneath. if (animator.mWin.isChildWindow() && animator.mWin.mSubLayer < 0 && animator.mWin.mAppToken != null) { mSurfaceControl = new SurfaceControlWithBackground(s, name, w, h, format, flags, animator.mWin.mAppToken); } else if (DEBUG_SURFACE_TRACE) { mSurfaceControl = new SurfaceTrace( s, name, w, h, format, flags); } else { mSurfaceControl = new SurfaceControl( s, name, w, h, format, flags); } }

SurfaceControl的构造函数里会请求SurfaceFlinger创建surface

public SurfaceControl(SurfaceSession session, String name, int w, int h, int format, int flags) throws OutOfResourcesException { if (session == null) { throw new IllegalArgumentException("session must not be null"); } if (name == null) { throw new IllegalArgumentException("name must not be null"); } if ((flags & SurfaceControl.HIDDEN) == 0) { Log.w(TAG, "Surfaces should always be created with the HIDDEN flag set " + "to ensure that they are not made visible prematurely before " + "all of the surface's properties have been configured. " + "Set the other properties and make the surface visible within " + "a transaction. New surface name: " + name, new Throwable()); } mName = name; mNativeObject = nativeCreate(session, name, w, h, format, flags); if (mNativeObject == 0) { throw new OutOfResourcesException( "Couldn't allocate SurfaceControl native object"); } mCloseGuard.open("release"); }

SurfaceControl.nativeCreate

static jlong nativeCreate(JNIEnv* env, jclass clazz, jobject sessionObj, jstring nameStr, jint w, jint h, jint format, jint flags) { ScopedUtfChars name(env, nameStr); sp<SurfaceComposerClient> client(android_view_SurfaceSession_getClient(env, sessionObj)); sp<SurfaceControl> surface = client->createSurface( String8(name.c_str()), w, h, format, flags); if (surface == NULL) { jniThrowException(env, OutOfResourcesException, NULL); return 0; } surface->incStrong((void *)nativeCreate); return reinterpret_cast<jlong>(surface.get()); }

具体SurfaceFlinger怎么创建surface的，可以参考[这篇文章][Link 1]

简单来说，就是在SurfaceFlinger中创建了Layer对象

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. */ 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), result(NO_ERROR), 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; } }; sp<MessageBase> msg = new MessageCreateLayer(mFlinger.get(), name, this, w, h, format, flags, handle, gbp); mFlinger->postMessageSync(msg); return static_cast<MessageCreateLayer*>( msg.get() )->getResult(); }

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) { ...... result = createNormalLayer(client, name, w, h, flags, format, handle, gbp, &layer); break; ....... }

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) { *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(); } }

Layer对象其实是包装了`IGraphicBufferProducer`和`IGraphicBufferConsumer`，consumer应该是指SurfaceFlinger，producer会传到应用那边，作为UI图像的生产者。

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); mProducer->setMaxDequeuedBufferCount(2); } sp<IBinder> Layer::getHandle() { Mutex::Autolock _l(mLock); LOG_ALWAYS_FATAL_IF(mHasSurface, "Layer::getHandle() has already been called"); mHasSurface = true; return new Handle(mFlinger, this); } sp<IGraphicBufferProducer> Layer::getProducer() const { return mProducer; }

SurfaceControl包装了handle和gbp

sp<SurfaceControl> SurfaceComposerClient::createSurface( const String8& name, uint32_t w, uint32_t h, PixelFormat format, uint32_t flags) { .... sur = new SurfaceControl(this, handle, gbp); ..... return sur; }

回到wms的relayout中，WindowSurfaceController会调用getSurface去填充outSurface。

WindowSurfaceController.getSurface

void getSurface(Surface outSurface) { outSurface.copyFrom(mSurfaceControl); }

Surface.java

public void copyFrom(SurfaceControl other) { .... long newNativeObject = nativeCreateFromSurfaceControl(surfaceControlPtr); synchronized (mLock) { if (mNativeObject != 0) { nativeRelease(mNativeObject); } setNativeObjectLocked(newNativeObject); } }

nativeCreateFromSurfaceControl将SurfaceControl中的surface拷贝到Surface中。这样ViewRootImpl就拥有了自己的Surface。

static jlong nativeCreateFromSurfaceControl(JNIEnv* env, jclass clazz, jlong surfaceControlNativeObj) { sp<SurfaceControl> ctrl(reinterpret_cast<SurfaceControl *>(surfaceControlNativeObj)); sp<Surface> surface(ctrl->getSurface()); if (surface != NULL) { surface->incStrong(&sRefBaseOwner); } return reinterpret_cast<jlong>(surface.get()); }

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; }

另外一个有趣的地方是，虽然ViewRoot的Surface和WMS的Surface在两个进程，所以这两个Surface是两个完全不同的东西。Surface在序列化传输时是吧GraphicBufferProducer这个binder进行序列化传输了。

[Image 1]: 
[Link 1]: https://link.jianshu.com?t=http%3A%2F%2Fblog.csdn.net%2Fluoshengyang%2Farticle%2Fdetails%2F7884628