宜宾商城网站建设,网站改版方案案例,建企业门户网站,网站改备案一、Surface 概述
OpenGL ES/Skia定义了一组绘制接口的规范#xff0c;为什么能够跨平台#xff1f; 本质上需要与对应平台上的本地窗口建立连接。也就是说OpenGL ES负责输入了绘制的命令#xff0c;但是需要一个 “画布” 来承载输出结果#xff0c;最终展示到屏幕。这个…一、Surface 概述
OpenGL ES/Skia定义了一组绘制接口的规范为什么能够跨平台 本质上需要与对应平台上的本地窗口建立连接。也就是说OpenGL ES负责输入了绘制的命令但是需要一个 “画布” 来承载输出结果最终展示到屏幕。这个画布就是本地窗口。
因此每个平台的有着不一样的本地窗口的实现。Android平台上是 ANativeWindow。
疑问
那么如何将OpenGL本地化 通过 EGL来对OpenGL ES来进行配置。关键点就是提供本地化窗口。本地化窗口的作用是什么 本地窗口是OpenGL ES和 物理屏幕之间的桥梁。
1.1 Android本地窗口简述
Android图形系统提供的本地窗口可以分为两类
FrameBufferNativeWindow
面对SF(SurfaceFlinger)。它通过HAL层的Gralloc系统调用(alloc/free)来分配内核中的FrameBuffer帧缓冲区。 这个帧缓冲区就代表了物理屏幕(fb驱动节点表示屏幕数。如fb0主屏幕、fb1等)。 FrameBuffer的数量一般情况下是2也就是双缓冲。当然还有三倍缓冲。
Surface
面向应用程序。对应的是内存中一块缓冲区称为GraphicBuffer。是由SF来进行分配。app从SF中获取一块GraphicBuffer 通过OpenGL/Skia将图形数据绘制(软件/硬件)到GraphicBuffer上。最终SF会把各个应用的GraphicBuffer数据进行合成最终 通过 FrameBufferNativeWindow 输出到屏幕上。
有了一个整体的概念接下来就好理解很多。
二、引出SurfaceSession
2.1 从WindowManagerImpl的addView()说起
app
WindowManagerImpl.addView()WindowManagerGlobal.addView()ViewRootImpl的setView()IWindowSession.addToDisplay()
WMS:new WindowStateWindowState.attach()session.windowAddedLocked()new SurfaceSession()复制代码
view添加到window的过程中 从WindowManagerImpl 的 addView()到WindowManagerGlobal(构造方法中会在system server 进程中创建一个Session对象)的addView()。最后会调用 ViewRootImpl的setView()方法。 内部会调用 IWindowSession 的addToDisplay() 方法。IWindowSession是WMS提供的一个binder服务(实现类就是Session)。
2.2 IWindowSession.windowAddedLocked()
内部会创建一个WindowState 对象。 调用 WindowState的 attach()方法。最终调到Session中的windowAddedLocked()会创建 一个SurfaceSession对象。这就是我们要找的的跟SurfaceFlinger建立联系的地方。 SurfaceSession mSurfaceSession;
void windowAddedLocked(String packageName) {mPackageName packageName;mRelayoutTag relayoutWindow: mPackageName;if (mSurfaceSession null) {// 一个进程只有一个session因此也只创建一次 SurfaceSession 对象
// 创建 SurfaceSession 对象mSurfaceSession new SurfaceSession();
// 每个session 都存入WMS中的mService.mSessions.add(this);
if (mLastReportedAnimatorScale ! mService.getCurrentAnimatorScale()) {mService.dispatchNewAnimatorScaleLocked(this);}}mNumWindow; // 进程中所有窗口的数量1
}复制代码
一个应用进程对应一个Session对象一个Session对象对应一个SurfaceSession。 WMS会把 这个Session 存储起来。也就是说WMS 会把所有跟SurfaceFlinger保持连接状态的应用Session存储起来。
2.3 SurfaceSession 创建过程
这个类的实例代表了和SurfaceFlinger的一个连接。我们可以通过它 创建一个或多个 Surface 对象。
2.3.1 构造方法 SurfaceSession.java
private long mNativeClient; // SurfaceComposerClient*
public SurfaceSession() {//native 方法mNativeClient nativeCreate();
}
frameworks/base/core/jni/android_view_SurfaceSession.cpp
static jlong nativeCreate(JNIEnv* env, jclass clazz) {// 新建一个 SurfaceComposerClient 对象SurfaceComposerClient* client new SurfaceComposerClient();client-incStrong((void*)nativeCreate);//返回SurfaceComposerClient对象的引用到java层。return reinterpret_castjlong(client);
}复制代码
SurfaceComposerClient 是什么呢
2.3.2 SurfaceComposerClient
在 SurfaceComposerClient第一次被引用的时候会走onFirstRef()方法。 frameworks/native/libs/gui/SurfaceComposerClient.cpp
void SurfaceComposerClient::onFirstRef() {//创建sf代理binder对象sf类型为 ISurfaceComposerspISurfaceComposer sf(ComposerService::getComposerService());if (sf ! nullptr mStatus NO_INIT) {spISurfaceComposerClient conn;//创建一个 ISurfaceComposerClient 对象用来跨进程调用conn sf-createConnection();if (conn ! nullptr) {mClient conn;mStatus NO_ERROR;}}
}复制代码
ISurfaceComposer 实现类就是 SurfaceFlinger对象。在server进程的代理对象是 ComposerService。This class defines the Binder IPC interface for accessing various SurfaceFlinger features.通过SF.createConnection(),创建一个 ISurfaceComposerClient 对象 mClient用来跨进程调用。
那么 ISurfaceComposerClient的实现类是哪个呢 继续看看 SF.createConnection()。
2.3.3 SurfaceFlinger.createConnection()
注意此时是在SF进程。frameworks/native/services/surfaceflinger/SurfaceFlinger.cpp
spISurfaceComposerClient SurfaceFlinger::createConnection() {// new client对象。return initClient(new Client(this));
}
static spISurfaceComposerClient initClient(const spClient client) {status_t err client-initCheck();if (err NO_ERROR) {// 返回该对象return client;}return nullptr;
}frameworks/native/services/surfaceflinger/Client.h
class Client : public BnSurfaceComposerClient{...class BnSurfaceComposerClient : public SafeBnInterfaceISurfaceComposerClient {...复制代码
原来ISurfaceComposerClient的实现类就是 SF中定义的 Client。也是一个binder服务。 我们回到 SurfaceComposerClient 类它持有 ISurfaceComposerClient的binder引用 mClient。通过 mClient实现与SF通信。
2.3 小结
Session 类中创建了一个 SurfaceSession 对象内部引用c层的 SurfaceComposerClient 对象。SurfaceComposerClient 对象是通过SF创建的另一个binder服务。减轻SF的工作量。SurfaceComposerClient 对象则通过 mClient成员(ISurfaceComposerClient)代理binder后续用来创建 Surface。
Surface绘制原理
Surface的Buffer是从哪里来的
源码frameworks/base/core/java/android/view/ViewRootImpl.java View触发绘制是通过requestLayout()函数或者setLayoutParms()函数 performTravsersals()函数实现
private void performTraversals() {……performMeasure(childWidthMeasureSpec, childHeightMeasureSpec);performLayout(lp, mWidth, mHeight);performDraw();……
}perfomrDraw()函数调用draw()函数开始绘制
private void performDraw() {……boolean canUseAsync draw(fullRedrawNeeded);……
}ViewRootImpl.draw()函数实现
private boolean draw(boolean fullRedrawNeeded) {Surface surface mSurface;……if (!drawSoftware(surface, mAttachInfo, xOffset, yOffset, scalingRequired, dirty, surfaceInsets)) {return false;}……return useAsyncReport;
}drawSoftware()软件绘制默认是软件绘制。
drawSoftware()函数软件绘制流程
private boolean drawSoftware(Surface surface, AttachInfo attachInfo, int xoff, int yoff,boolean scalingRequired, Rect dirty, Rect surfaceInsets) {
// Draw with software renderer.final Canvas canvas;……canvas mSurface.lockCanvas(dirty);……mView.draw(canvas);……surface.unlockCanvasAndPost(canvas);
}获取通过lockCanvas函数获取Canvas对象
绘制再通过mView.draw(canvas)函数向在canvas上绘制
提交最后通过surface.unlockCanvasAndPost(canvas)函数提交Canvas。
通过lockCanvas()函数获取Canvas对象lockCanvas()函数如何获取Canvas对象。
lockCanvas()函数实现
/*** Gets a {link Canvas} for drawing into this surface.** After drawing into the provided {link Canvas}, the caller must* invoke {link #unlockCanvasAndPost} to post the new contents to the surface.** param inOutDirty A rectangle that represents the dirty region that the caller wants* to redraw. This function may choose to expand the dirty rectangle if for example* the surface has been resized or if the previous contents of the surface were* not available. The caller must redraw the entire dirty region as represented* by the contents of the inOutDirty rectangle upon return from this function.* The caller may also pass codenull/code instead, in the case where the* entire surface should be redrawn.* return A canvas for drawing into the surface.** throws IllegalArgumentException If the inOutDirty rectangle is not valid.* throws OutOfResourcesException If the canvas cannot be locked.*/
public Canvas lockCanvas(Rect inOutDirty)throws Surface.OutOfResourcesException, IllegalArgumentException {synchronized (mLock) {checkNotReleasedLocked();if (mLockedObject ! 0) {// Ideally, nativeLockCanvas() would throw in this situation and prevent the// double-lock, but that wont happen if mNativeObject was updated. We cant// abandon the old mLockedObject because it might still be in use, so instead// we just refuse to re-lock the Surface.throw new IllegalArgumentException(Surface was already locked);}mLockedObject nativeLockCanvas(mNativeObject, mCanvas, inOutDirty);return mCanvas;}
}通过Native层android_view_Surface.cpp的nativeLockCanvas(mNativeObject, mCanvas, inOutDirty)函数获取mNativeOjbect参数是Java层的Surface在Native层对应的Surface对象的指针。mCanvas是Surface的变量在lockCanvas()函数调用时mCanvas是空的。
在调用nativeLockCanvas()函数后mCanvas就有值了最后返回mCanvas对象。
static jlong nativeLockCanvas(JNIEnv* env, jclass clazz,jlong nativeObject, jobject canvasObj, jobject dirtyRectObj) {// (1)spSurface surface(reinterpret_castSurface *(nativeObject));……// (2)ANativeWindow_Buffer buffer;status_t err surface-lock(buffer, dirtyRectPtr);……// (3)graphics::Canvas canvas(env, canvasObj);canvas.setBuffer(buffer, static_castint32_t(surface-getBuffersDataSpace()));……// (4)// Create another reference to the surface and return it. This reference// should be passed to nativeUnlockCanvasAndPost in place of mNativeObject,// because the latter could be replaced while the surface is locked.spSurface lockedSurface(surface);lockedSurface-incStrong(sRefBaseOwner);return (jlong) lockedSurface.get();
}(1) 获取Native层的Surface对象。
(2) 获取Native层的Surface对象的Buffer。
(3) 将Buffer设置给Canvas这里Canvas就有一个Buffer了。在每次都申请一个新的Buffer给Canvas对象。
(4) 向Java层返回Native的Surface对象这里返回的是一个Long型数据这个Long型数据是Surface指针。
获取Buffer实现surface - lock(buffer, )这里传入Buffer地址
源码frameworks/native/libs/gui/Surface.cpp
status_t Surface::lock(ANativeWindow_Buffer* outBuffer, ARect* inOutDirtyBounds)
{……// (1)ANativeWindowBuffer* out;status_t err dequeueBuffer(out, fenceFd);……// (2)spGraphicBuffer backBuffer(GraphicBuffer::getSelf(out));……// (3)void* vaddr;status_t res backBuffer-lockAsync(GRALLOC_USAGE_SW_READ_OFTEN | GRALLOC_USAGE_SW_WRITE_OFTEN, newDirtyRegion.bounds(), vaddr, fenceFd);……// (4)mLockedBuffer backBuffer;// (5)outBuffer-bits vaddr;……
}(1) 获取dequeueBuffer()函数在SurfaceFlinger的Buffer队列中获取Buffer。
(2) 创建GraphicBuffer对象backBuffer。在SharedBufferStack中有双缓冲机制分别为FontBuffer和BackBuffer。
FontBuffer代表当前将显示在屏幕的Buffer数据。属于前台Buffer。 BackBuffer代表绘制的Buffer数据是准备渲染的数据Buffer。属于后台Buffer。 (3) 锁定Buffer并将Buffer地址返回将返回的Buffer地址给Canvas的Buffer。
(4) 切换Buffer将后台BackBuffer切换到前台交给mLockedBuffer。FontBuffer的变量就是mLockedBuffer。
(5) 将vaddr赋值给outBuffer-bitsbits最后赋值给Canvas的Buffer就是BkBitmap作为Canvas的缓冲区。
dequeteBuffer()是如何获取Buffer的dequeteBuffer()函数实现
int Surface::dequeueBuffer(android_native_buffer_t** buffer, int* fenceFd) {……int buf -1;// (1)status_t result mGraphicBufferProducer-dequeueBuffer(buf, fence, reqWidth, reqHeight,reqFormat, reqUsage, mBufferAge,enableFrameTimestamps ? frameTimestamps: nullptr);……// (2)spGraphicBuffer gbuf(mSlots[buf].buffer);……// (3)if ((result IGraphicBufferProducer::BUFFER_NEEDS_REALLOCATION) || gbuf nullptr) {if (mReportRemovedBuffers (gbuf ! nullptr)) {mRemovedBuffers.push_back(gbuf);}result mGraphicBufferProducer-requestBuffer(buf, gbuf);if (result ! NO_ERROR) {ALOGE(dequeueBuffer: IGraphicBufferProducer::requestBuffer failed: %d, result);mGraphicBufferProducer-cancelBuffer(buf, fence);return result;}}……// (4)*buffer gbuf.get();
}(1) 通过mGaphicBufferProducer-dequeteBuffer()函数在远端的Buffer slots中获得一个空闲的Buffer返回远端Buffer地址指针。
(2) 通过gbp从本地Buffer Slots里获取Buffer在(1)中从远端在(2)中从本地这里涉及远端Buffer queue与本地Buffer queue同步问题。
(3) 负责本地Buffer与远端Buffer同步远端返回的Buffer的result是BUFFER_NEEDS_REALLOCATION或者本地的gbp是null通过gbp的requestBuffer()获取新的远端Buffer指针地址。mGaphicBufferProducer-requestBuffer()函数。
(4) 获取Buffer。
Surface的Buffer是如何提交的
通过surface.unlockCanvasAndPost(canvas)向远端提交更新的BufferunlockCanvasAndPost()函数实现
/*** Posts the new contents of the {link Canvas} to the surface and* releases the {link Canvas}.** param canvas The canvas previously obtained from {link #lockCanvas}.*/
public void unlockCanvasAndPost(Canvas canvas) {synchronized (mLock) {unlockSwCanvasAndPost(canvas);}
}
private void unlockSwCanvasAndPost(Canvas canvas) {try {nativeUnlockCanvasAndPost(mLockedObject, canvas);} finally {nativeRelease(mLockedObject);mLockedObject 0;}
}最后调用到Native层的nativeUnlockCanvasAndPost(mLockedObject, canvas)。
Native层nativeUnlockCanvasAndPost()函数实现
static void nativeUnlockCanvasAndPost(JNIEnv* env, jclass clazz,jlong nativeObject, jobject canvasObj) {// (1)spSurface surface(reinterpret_castSurface *(nativeObject));
// (2)// detach the canvas from the surfacegraphics::Canvas canvas(env, canvasObj);canvas.setBuffer(nullptr, ADATASPACE_UNKNOWN);// (3)// unlock surfacestatus_t err surface-unlockAndPost();
}(1) 获取对应Java层的Native层的Surface对象。
(2) 获取对应Java层的Native层的Canvas对象。
(3) 将本地Buffer更新到远端的Buffer queue中。
Native层更新远端Buffer queuesurface-unlockAndPost()函数实现
源码frameworks/native/libs/gui/Surface.cpp
status_t Surface::unlockAndPost()
{if (mLockedBuffer nullptr) {ALOGE(Surface::unlockAndPost failed, no locked buffer);return INVALID_OPERATION;}
int fd -1;status_t err mLockedBuffer-unlockAsync(fd);ALOGE_IF(err, failed unlocking buffer (%p), mLockedBuffer-handle);err queueBuffer(mLockedBuffer.get(), fd);ALOGE_IF(err, queueBuffer (handle%p) failed (%s),mLockedBuffer-handle, strerror(-err));mPostedBuffer mLockedBuffer;mLockedBuffer nullptr;return err;
}通过函数queueBuffer(mLockedBuffer.get(), )函数实现更新
int Surface::queueBuffer(android_native_buffer_t* buffer, int fenceFd) {……// (1)int i getSlotFromBufferLocked(buffer);……// (2)status_t err mGraphicBufferProducer-queueBuffer(i, input, output);……return err;
}(1) 获取Buffer的index。
(2) 通过mGraphicBufferProducer-queueBuffer(i, )函数将本地的Buffer同步到远端Buffer queue中。 以上为车载技术中Window Display板块的surface的绘制过程与原理更多车载技术参考可点击《车载技术手册》查看类目学习。
Android车载学习手册docs.qq.com/doc/DUldvclB5d0JZSVFn
三、总结
