BootAnimation使用surfaceflinger分析

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本文详细解析了Android系统中BootAnimation的启动流程，包括通过init.rc配置启动BootAnimation服务、创建Surface并设置图层，以及如何初始化OpenGL进行渲染。

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

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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

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

首先创建 SurfaceFilinger Client；

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

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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。

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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

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

告诉surfaceflinger service 获取DisplayId的Binder

rameworks/native/libs/gui/ISurfaceComposer.cpp

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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;

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

同样看SurfaceFlinger.cpp

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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

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

接着

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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