BootAnimation使用surfaceflinger分析

首先，从BootAnimation开始分析，BootAnimation在启动脚本init。Rc被配置成一个服务

1.service bootanim /system/bin/bootanimation
2.    class main
3.    user graphics
4.    group system audio graphics cw_access
5.    disabled
6.    oneshot

而其代码在 frameworks/cmds/bootanimation

int main(int argc, char** argv)

{

#if defined(HAVE_PTHREADS)

    setpriority(PRIO_PROCESS, 0, ANDROID_PRIORITY_DISPLAY);

#endif

    char value[PROPERTY_VALUE_MAX];

    property_get("debug.sf.nobootanimation", value, "0");

    int noBootAnimation = atoi(value);

    ALOGI_IF(noBootAnimation,  "boot animation disabled");

    if (!noBootAnimation) {

        sp<ProcessState> proc(ProcessState::self());

        ProcessState::self()->startThreadPool();

        // create the boot animation object

        sp<BootAnimation> boot = new BootAnimation();

        IPCThreadState::self()->joinThreadPool();

    }

    return 0;

}

从代码可以看出，bootanimation的启动是通过new一个BootAnimation

BootAnimation::BootAnimation() : Thread(false)
{
    mSession = new SurfaceComposerClient();
}

首先 创建 SurfaceFilinger Client；

========================================

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);
    }
}

可以看出BootAnimation最终继承了RefBase，在main函数里的boot 是一个sp 的智能指针，

第一次对 BootAnimation 引用调用sp<BootAnimation>时 会调用 BootAnimation 的onFirstRef()方法；

最后 调用run，让BootAnimation线程跑起来，Thread会先跑到readyToRun（），然后再跑:threadLoop()

而SurfaceComposerClient的linkToComposerDeath函数获取了SurfaceFlinger服务，

linkTocomposerDeath的作用是 当surfaceflinger死掉时，当前Bootanimation service 就会得到通知，会自动调用 BootAnimation::binderDied。  

tatus_t BootAnimation::readyToRun() {
    mAssets.addDefaultAssets();

    sp<IBinder> dtoken(SurfaceComposerClient::getBuiltInDisplay(
            ISurfaceComposer::eDisplayIdMain));
    DisplayInfo dinfo;
    status_t status = SurfaceComposerClient::getDisplayInfo(dtoken, &dinfo);
    if (status)
        return -1;

    // create the native surface
    sp<SurfaceControl> control = session()->createSurface(String8("BootAnimation"),
            dinfo.w, dinfo.h, PIXEL_FORMAT_RGB_565);

    SurfaceComposerClient::openGlobalTransaction();
    control->setLayer(0x40000000);  //设置图层；
    SurfaceComposerClient::closeGlobalTransaction();

    sp<Surface> s = control->getSurface();

    // initialize opengl and egl
    const EGLint attribs[] = {
            EGL_RED_SIZE,   8,
            EGL_GREEN_SIZE, 8,
            EGL_BLUE_SIZE,  8,
            EGL_DEPTH_SIZE, 0,
            EGL_NONE
    };
    EGLint w, h, dummy;
    EGLint numConfigs;
    EGLConfig config;
    EGLSurface surface;
    EGLContext context;

    EGLDisplay display = eglGetDisplay(EGL_DEFAULT_DISPLAY);

    eglInitialize(display, 0, 0);
    eglChooseConfig(display, attribs, &config, 1, &numConfigs);
    surface = eglCreateWindowSurface(display, config, s.get(), NULL);
    context = eglCreateContext(display, config, NULL, NULL);
    eglQuerySurface(display, surface, EGL_WIDTH, &w);
    eglQuerySurface(display, surface, EGL_HEIGHT, &h);

    if (eglMakeCurrent(display, surface, surface, context) == EGL_FALSE)
        return NO_INIT;
   mDisplay = display;
    mContext = context;
    mSurface = surface;
    mWidth = w;
    mHeight = h;
    mFlingerSurfaceControl = control;
    mFlingerSurface = s;

    mAndroidAnimation = true;

    // If the device has encryption turned on or is in process
    // of being encrypted we show the encrypted boot animation.
    char decrypt[PROPERTY_VALUE_MAX];
    property_get("vold.decrypt", decrypt, "");

    bool encryptedAnimation = atoi(decrypt) != 0 || !strcmp("trigger_restart_min_framework", decrypt);

    if ((encryptedAnimation &&
            (access(SYSTEM_ENCRYPTED_BOOTANIMATION_FILE, R_OK) == 0) &&
            (mZip.open(SYSTEM_ENCRYPTED_BOOTANIMATION_FILE) == NO_ERROR)) ||

            ((access(USER_BOOTANIMATION_FILE, R_OK) == 0) &&
            (mZip.open(USER_BOOTANIMATION_FILE) == NO_ERROR)) ||

            ((access(SYSTEM_BOOTANIMATION_FILE, R_OK) == 0) &&
            (mZip.open(SYSTEM_BOOTANIMATION_FILE) == NO_ERROR))) {
        mAndroidAnimation = false;
    }

    return NO_ERROR;
}

首先，通过向surfaceflinger service发送

sp<IBinder> dtoken(SurfaceComposerClient::getBuiltInDisplay(
            ISurfaceComposer::eDisplayIdMain));

告诉surfaceflinger service 获取DisplayId的Binder

rameworks/native/libs/gui/ISurfaceComposer.cpp

class BpSurfaceComposer : public BpInterface<ISurfaceComposer>
{
   ...
virtual sp<IBinder> getBuiltInDisplay(int32_t id)
    {
        Parcel data, reply;
        data.writeInterfaceToken(ISurfaceComposer::getInterfaceDescriptor());
        data.writeInt32(id);
        remote()->transact(BnSurfaceComposer::GET_BUILT_IN_DISPLAY, data, &reply);
        return reply.readStrongBinder();
    }
 ....
};

status_t BnSurfaceComposer::onTransact(
    uint32_t code, const Parcel& data, Parcel* reply, uint32_t flags)
{
switch(code) {
case GET_BUILT_IN_DISPLAY: {
            CHECK_INTERFACE(ISurfaceComposer, data, reply);
            int32_t id = data.readInt32();
            sp<IBinder> display(getBuiltInDisplay(id));
            reply->writeStrongBinder(display);
            return NO_ERROR;
        } break;
}
}

接着获取一个 DisplayInfo dinfo;

status_t status = SurfaceComposerClient::getDisplayInfo(dtoken, &dinfo);

同样看SurfaceFlinger.cpp

status_t SurfaceFlinger::getDisplayInfo(const sp<IBinder>& display, DisplayInfo* info)
{
    int32_t type = NAME_NOT_FOUND;
    for (int i=0 ; i<DisplayDevice::NUM_DISPLAY_TYPES ; i++) {
        if (display == mBuiltinDisplays[i]) {
            type = i;
            break;
        }
    }

    if (type < 0) {
        return type;
    }

    const HWComposer& hwc(getHwComposer());
    float xdpi = hwc.getDpiX(type);
    float ydpi = hwc.getDpiY(type);

    // TODO: Not sure if display density should handled by SF any longer
    class Density {
        static int getDensityFromProperty(char const* propName) {
            char property[PROPERTY_VALUE_MAX];
            int density = 0;
            if (property_get(propName, property, NULL) > 0) {
                density = atoi(property);
            }
            return density;
        }
    public:
        static int getEmuDensity() {
            return getDensityFromProperty("qemu.sf.lcd_density"); }
        static int getBuildDensity()  {
            return getDensityFromProperty("ro.sf.lcd_density"); }
    };

    if (type == DisplayDevice::DISPLAY_PRIMARY) {
        // The density of the device is provided by a build property
        float density = Density::getBuildDensity() / 160.0f;
        if (density == 0) {
            // the build doesn't provide a density -- this is wrong!
            // use xdpi instead
            ALOGE("ro.sf.lcd_density must be defined as a build property");
            density = xdpi / 160.0f;
        }
        if (Density::getEmuDensity()) {
            // if "qemu.sf.lcd_density" is specified, it overrides everything
            xdpi = ydpi = density = Density::getEmuDensity();
            density /= 160.0f;
        }
        info->density = density;

        // TODO: this needs to go away (currently needed only by webkit)
        sp<const DisplayDevice> hw(getDefaultDisplayDevice());
        info->orientation = hw->getOrientation();
        getPixelFormatInfo(hw->getFormat(), &info->pixelFormatInfo);
    } else {
        // TODO: where should this value come from?
        static const int TV_DENSITY = 213;
        info->density = TV_DENSITY / 160.0f;
        info->orientation = 0;
    }

    info->w = hwc.getWidth(type);
    info->h = hwc.getHeight(type);
    info->xdpi = xdpi;
    info->ydpi = ydpi;
    info->fps = float(1e9 / hwc.getRefreshPeriod(type));

    // All non-virtual displays are currently considered secure.
    info->secure = true;

    return NO_ERROR;
}

接着，按返回的DisplayInfo创建一个native surface

/ create the native surface
    sp<SurfaceControl> control = session()->createSurface(String8("BootAnimation"),
            dinfo.w, dinfo.h, PIXEL_FORMAT_RGB_565);

接着

SurfaceComposerClient::openGlobalTransaction();  //增加一个 全局Transaction计数
    control->setLayer(0x40000000);  //设置图层；
SurfaceComposerClient::closeGlobalTransaction();  //减少一个全局Transaction计数,当这个全局Transaction计数减少至0的时候，把mStates发送给SurfaceFlinger处理

setLayer从代码里看是设置z-order，层级越高越接近客户

设置完Z-order后

sp<Surface> s = control->getSurface();

通过SurfaceControl获取了一个Surface

sp<Surface> SurfaceControl::getSurface() const
{
    Mutex::Autolock _l(mLock);
    if (mSurfaceData == 0) {
        mSurfaceData = new Surface(mGraphicBufferProducer);
    }
    return mSurfaceData;
}

Surface的创建则通过createsurface时创建的mGraphicBufferProducer(SurfaceTextureLayer)来初始化

Surface::Surface(
        const sp<IGraphicBufferProducer>& bufferProducer)
    : mGraphicBufferProducer(bufferProducer)
{
    // Initialize the ANativeWindow function pointers.
    ANativeWindow::setSwapInterval  = hook_setSwapInterval;
    ANativeWindow::dequeueBuffer    = hook_dequeueBuffer;
    ANativeWindow::cancelBuffer     = hook_cancelBuffer;
    ANativeWindow::queueBuffer      = hook_queueBuffer;
    ANativeWindow::query            = hook_query;
    ANativeWindow::perform          = hook_perform;

    ANativeWindow::dequeueBuffer_DEPRECATED = hook_dequeueBuffer_DEPRECATED;
    ANativeWindow::cancelBuffer_DEPRECATED  = hook_cancelBuffer_DEPRECATED;
    ANativeWindow::lockBuffer_DEPRECATED    = hook_lockBuffer_DEPRECATED;
    ANativeWindow::queueBuffer_DEPRECATED   = hook_queueBuffer_DEPRECATED;

    const_cast<int&>(ANativeWindow::minSwapInterval) = 0;
    const_cast<int&>(ANativeWindow::maxSwapInterval) = 1;

    mReqWidth = 0;
    mReqHeight = 0;
    mReqFormat = 0;
    mReqUsage = 0;
    mTimestamp = NATIVE_WINDOW_TIMESTAMP_AUTO;
    mCrop.clear();
    mScalingMode = NATIVE_WINDOW_SCALING_MODE_FREEZE;
    mTransform = 0;
    mDefaultWidth = 0;
    mDefaultHeight = 0;
    mUserWidth = 0;
    mUserHeight = 0;
    mTransformHint = 0;
    mConsumerRunningBehind = false;
    mConnectedToCpu = false;
}

接着通过这个surface对象初始化egl

surface = eglCreateWindowSurface(display, config, s.get(), NULL);

其他都是走egl流程

然后，继续分析BootAnimation，跑完systemReadyRun，则会跑threadloop循环

bool BootAnimation::threadLoop()
{
    bool r;
    if (mAndroidAnimation) {
        r = android();
    } else {
        r = movie();
    }

    // No need to force exit anymore
    property_set(EXIT_PROP_NAME, "0");

    eglMakeCurrent(mDisplay, EGL_NO_SURFACE, EGL_NO_SURFACE, EGL_NO_CONTEXT);
    eglDestroyContext(mDisplay, mContext);
    eglDestroySurface(mDisplay, mSurface);
    mFlingerSurface.clear();
    mFlingerSurfaceControl.clear();
    eglTerminate(mDisplay);
    IPCThreadState::self()->stopProcess();
    return r;
}

可以看出，如果mAndroidAnimation为true则跑Android，不成功则跑movie