skia

[074]RenderEngineType简介

前⾔

RenderEngine是⼀个静态库，主要作⽤于SurfaceFlinger进⾏clientlayer合成。

简单理解就是将clientbufferlayer合成到FramebufferSurface

frameworksnativelibsrenderengine

⼀、RenderEngineType

RenderEngineType是指RenderEngine的合成⽅式实现类型，⽬前有四种类型实现如下。

enumclassRenderEngineType{

GLES=1,//opengl

THREADED=2,//opengl异步线程

SKIA_GL=3,//skia

SKIA_GL_THREADED=4,//skia异步线程

};

同步异步

skiaSKIA_GLSKIA_GL_THREADED

openglGLESTHREADED

异步的意思会另起⼀个名叫RenderEngine的线程中处理合成任务。

同步的意思是会在SurfaceFlinger的主线程中处理合成任务

如图：异步处理合成任务的Trace。

⼆、RenderEngine初始化流程

基于最新的代码安卓代码

SurfaceFlingerinit的时候会构建RenderEngine，并且确认RenderEngineType

frameworks/native/services/surfaceflinger/

voidSurfaceFlinger::init(){

...

//GetaRenderEngineforthegivendisplay/config(can'tfail)

//TODO(b/77156734):WeneedtostopcastinganduseHALtypeswhenpossible.

//SendingmaxFrameBufferAcquiredBuffersasthecachesizeistightlytunedtosingle-display.

mCompositionEngine->setRenderEngine(renderengine::RenderEngine::create(

renderengine::RenderEngineCreationArgs::Builder()

.setPixelFormat(static_cast(defaultCompositionPixelFormat))

.setImageCacheSize(maxFrameBufferAcquiredBuffers)

.setUseColorManagerment(useColorManagement)

.setEnableProtectedContext(enable_protected_contents(false))

.setPrecacheToneMapperShaderOnly(false)

.setSupportsBackgroundBlur(mSupportsBlur)

.setContextPriority(

useContextPriority

renderengine::RenderEngine::ContextPriority::REALTIME

:renderengine::RenderEngine::ContextPriority::MEDIUM)

.build()));//跳转到1.2

mMaxRenderTargetSize=

std::min(getRenderEngine().getMaxTextureSize(),getRenderEngine().getMaxViewportDims());

....

}

1.2RenderEngine

提供了setRenderEngineType的接⼝，默认缺省值是SKIA_GL_THREADED

frameworks/native/libs/renderengine/include/renderengine/RenderEngine.h

structRenderEngineCreationArgs::Builder{

...

Builder&setRenderEngineType(RenderEngine::RenderEngineTyperenderEngineType){

this->renderEngineType=renderEngineType;

return*this;

}

...

private:

//1meansRGBA_8888

intpixelFormat=1;

uint32_timageCacheSize=0;

booluseColorManagement=true;

boolenableProtectedContext=false;

boolprecacheToneMapperShaderOnly=false;

boolsupportsBackgroundBlur=false;

RenderEngine::ContextPrioritycontextPriority=RenderEngine::ContextPriority::MEDIUM;

RenderEngine::RenderEngineTyperenderEngineType=

RenderEngine::RenderEngineType::SKIA_GL_THREADED;//缺省值

};

}//namespacerenderengine

可以通过设置"d"，改变RenderEngineType。

配置项：gles,threaded,skiagl,skiaglthread分别对应四种类型

frameworks/native/libs/renderengine/

#definePROPERTY_DEBUG_RENDERENGINE_BACKEND"d"

std::unique_ptrRenderEngine::create(RenderEngineCreationArgsargs){

//KeeptheabilitytooverridebyPROPERTIES:

charprop[PROPERTY_VALUE_MAX];

property_get(PROPERTY_DEBUG_RENDERENGINE_BACKEND,prop,"");

if(strcmp(prop,"gles")==0){

EngineType=RenderEngineType::GLES;

}

if(strcmp(prop,"threaded")==0){

EngineType=RenderEngineType::THREADED;

}

if(strcmp(prop,"skiagl")==0){

EngineType=RenderEngineType::SKIA_GL;

}

if(strcmp(prop,"skiaglthreaded")==0){

EngineType=RenderEngineType::SKIA_GL_THREADED;

}

switch(EngineType){

caseRenderEngineType::THREADED:

ALOGD("ThreadedRenderEnginewithGLESBackend");

returnrenderengine::threaded::RenderEngineThreaded::create(

[args](){returnandroid::renderengine::gl::GLESRenderEngine::create(args);},

EngineType);

caseRenderEngineType::SKIA_GL:

ALOGD("RenderEnginewithSkiaGLBackend");

returnrenderengine::skia::SkiaGLRenderEngine::create(args);

caseRenderEngineType::SKIA_GL_THREADED:{

ALOGD("ThreadedRenderEnginewithSkiaGLBackend");

returnrenderengine::threaded::RenderEngineThreaded::create(

[args](){

returnandroid::renderengine::skia::SkiaGLRenderEngine::create(args);

},

EngineType);

}

caseRenderEngineType::GLES:

default:

ALOGD("RenderEnginewithGLESBackend");

returnrenderengine::gl::GLESRenderEngine::create(args);

}

}

三、⼩结

androidS以后原⽣配置的是SKIA_GL_THREADED，⽬前窗⼝的blurs效果，只在skia实现上

opengl模式不⽀持blurs。

Somenewfeatures(indowblurs)areonlyimplementedinSkia

evicescanstill

turnitoffwithPROPERTY_DEBUG_RENDERENGINE_BACKEND.

细⼼你可能会发现前⾯SKIA_GL_THREADED的drawlayers中并没有发挥异步的作⽤。本质上还是会BlockSF的主线程。

⽬前我只发现REThreaded::unmapExternalTextureBuffer这个⽅法是异步处理了，相⽐SKIA_GL，有⼀定程度上的性能提升。

但是据说可能⼀些极限情况的下并发读写的问题，我相信后续android会不断的完善SKIA_GL_THREADED，后续可能就渐渐放弃GLES了。