ANativeWindow

ANativeWindow : opengl工作的绘图画布本地窗口，按标准定义好函数（下面好多代码都简化）

struct ANativeWindow

{

.....

//上层定义好函数指针，传给opengl后，opengl在必要的时候会调用相应的函数

int (* dequeueBuffer )( struct ANativeWindow * window ,

struct ANativeWindowBuffer ** buffer , int * fenceFd );

int (* queueBuffer )( struct ANativeWindow * window ,

struct ANativeWindowBuffer * buffer , int fenceFd );

int (* cancelBuffer )( struct ANativeWindow * window ,

struct ANativeWindowBuffer * buffer , int fenceFd );

}

ANativeWindowBuffer:绘制的图像缓冲区

struct ANativeWindowBuffer

{

int width ;

int height ;

int usage ;

.....

//通过这个handle就跟Gralloc模块申请的图片缓存关联起来了，可能在fb申请也能是共享内存中申请的（看他了 usage ）

buffer_handle_t handle ;

}

fenceFd：暂时把他当作这个buffer的锁，因为缓存区需要cpu,gpu,composer共享，普通锁不管用啊。

2. android中的本地窗口

(1.)操作显存的，surfaceflinger服务中应用的。最总渲染到屏幕的

FramebufferNativeWindow : public ANativeObjectBase <

ANativeWindow , FramebufferNativeWindow ,

LightRefBase < FramebufferNativeWindow > >

别看上面的这么复杂其实就是 FramebufferNativeWindow: public ANativeWindow,看名字就是包装了fb显存了，用它直接绘制到屏幕上的

构造函数:

FramebufferNativeWindow :: FramebufferNativeWindow ()

: BASE (), fbDev (0), grDev (0), mUpdateOnDemand ( false )

{

hw_module_t const * module ;

//打开Gralloc硬件抽象层模块

hw_get_module ( GRALLOC_HARDWARE_MODULE_ID , & module );

//获取抽象层中的fb设备定义，渲染到屏幕的

f ramebuffer_open ( module , & fbDev );

//获取抽象层图像缓存申请设备，获取一段内存或显存的

gralloc_open ( module , & grDev );

//看一下fb支持缓冲区大小，可能有多个离屏缓冲，初始化一下这些缓冲区

if ( fbDev -> numFramebuffers >= MIN_NUM_FRAME_BUFFERS && fbDev -> numFramebuffers <= MAX_NUM_FRAME_BUFFERS ){

mNumBuffers = fbDev -> numFramebuffers ;

} else {

mNumBuffers = MIN_NUM_FRAME_BUFFERS ;

}

for ( i = 0; i < mNumBuffers ; i ++)

{

// NativeBuffer : public ANativeWindowBuffer 从ANativeWindowBuffer继承

buffers [ i ] = new NativeBuffer ( fbDev -> width , fbDev -> height , fbDev -> format , GRALLOC_USAGE_HW_FB );

grDev -> alloc ( grDev , fbDev -> width , fbDev -> height , fbDev -> format , GRALLOC_USAGE_HW_FB , & buffers [ i ]-> handle , & buffers [ i ]-> stride );

}

//opengl需要的本地窗口定义了

const_cast < uint32_t &>( ANativeWindow :: flags ) = fbDev -> flags ;

const_cast < float &>( ANativeWindow :: xdpi ) = fbDev -> xdpi ;

const_cast < float &>( ANativeWindow :: ydpi ) = fbDev -> ydpi ;

const_cast < int &>( ANativeWindow :: minSwapInterval ) = fbDev -> minSwapInterval ;

const_cast < int &>( ANativeWindow :: maxSwapInterval ) = fbDev -> maxSwapInterval ;

ANativeWindow :: setSwapInterval = setSwapInterval ;

ANativeWindow :: dequeueBuffer = dequeueBuffer ;

ANativeWindow :: queueBuffer = queueBuffer ;

ANativeWindow :: query = query ;

ANativeWindow :: perform = perform ;

ANativeWindow :: dequeueBuffer_DEPRECATED = dequeueBuffer_DEPRECATED ;

ANativeWindow :: lockBuffer_DEPRECATED = lockBuffer_DEPRECATED ;

ANativeWindow :: queueBuffer_DEPRECATED = queueBuffer_DEPRECATED ;

}

int FramebufferNativeWindow :: setSwapInterval ( ANativeWindow * window , int interval )

{

return fb -> setSwapInterval ( fb , interval );

}

//opengl要一个图像缓冲区，要后台绘制了

int FramebufferNativeWindow :: dequeueBuffer ( ANativeWindow * window , ANativeWindowBuffer ** buffer , int * fenceFd )

{

//根据一系列条件找到一个空闲的缓冲区，如果没有空闲的了，还的等待queuebuffer释放一个缓存

int index =???

* buffer = self -> buffers [ index ]. get ();

* fenceFd = -1;

}

//这个buffer绘制完成，可以绘制到屏幕上了

int FramebufferNativeWindow :: queueBuffer ( ANativeWindow * window , ANativeWindowBuffer * buffer , int fenceFd )

{

//等待其他硬件都这个buffer操作完成

sp < Fence > fence ( new Fence ( fenceFd ));

fence -> wait ( Fence :: TIMEOUT_NEVER );

//绘制到屏幕上

fb -> post ( fb , handle );

}

egl中定义了:

typedef struct ANativeWindow * EGLNativeWindowType ;

（2.）app端，临时用的的ANativeWindow,最终这个buffer会间接的提交到Framebuffer那面，显示到屏幕上。

class Surface : public ANativeObjectBase < ANativeWindow , Surface , RefBase >

构造函数，跟上面的差不多吧，都先初始化ANativeWindow相关函数接口

Surface :: Surface ( const sp < IGraphicBufferProducer >& bufferProducer , bool controlledByApp )

: mGraphicBufferProducer ( bufferProducer )

{

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;

.....

}

//opengl要一个图像缓冲区，要后台绘制了

int Surface :: dequeueBuffer ( android_native_buffer_t ** buffer , int * fenceFd ) {

sp < Fence > fence ;

// producer(BufferQueue)中获取一段空闲的图像缓冲区,这个内部也是通过硬件抽象层的Gralloc申请的

status_t result = mGraphicBufferProducer -> dequeueBuffer (& buf , & fence , mSwapIntervalZero , reqW , reqH , mReqFormat , mReqUsage );

sp < GraphicBuffer >& gbuf ( mSlots [ buf ]. buffer );

if (( result & IGraphicBufferProducer :: BUFFER_NEEDS_REALLOCATION ) || gbuf == 0) {

result = mGraphicBufferProducer -> requestBuffer ( buf , & gbuf );

}

* fenceFd = fence -> dup ();

* buffer = gbuf . get ();

return OK ;

}

//这个buffer绘制完成，可以用了啊

int Surface :: queueBuffer ( android_native_buffer_t * buffer , int fenceFd ) {

Rect crop ;

mCrop . intersect ( Rect ( buffer -> width , buffer -> height ), & crop );

sp < Fence > fence ( fenceFd >= 0 ? new Fence ( fenceFd ) : Fence :: NO_FENCE );

IGraphicBufferProducer :: QueueBufferOutput output ;

IGraphicBufferProducer :: QueueBufferInput input ( timestamp , isAutoTimestamp ,

crop , mScalingMode , mTransform , mSwapIntervalZero , fence );

// producer(BufferQueue)添加一段填充好的buffer,需要渲染buffer的就看着办吧

status_t err = mGraphicBufferProducer-> queueBuffer(i , input, &output);

uint32_t numPendingBuffers = 0;

output . deflate (& mDefaultWidth , & mDefaultHeight , & mTransformHint ,

& numPendingBuffers );

return err ;

}

mGraphicBufferProducer （BufferQueue）入队，出队是一个跨进程的操作，他们通过Binder通讯。

BufferQueue是一个典型的生产消费结构，生产者加工好数据丢进来，消耗者发现有数据后马上消耗掉，这个以后再分析。

3.opengl如何使用这个ANativeWindow的呢

android中opengl环境的搭建是由EGL帮忙完成的，opengl是一组跨进程的api,

NativeWindowType就是一个 ANativeWindow

typedef struct ANativeWindow * EGLNativeWindowType ;

EGLSurface eglCreateWindowSurface ( EGLDisplay dpy , EGLConfig config , NativeWindowType window , const EGLint * attrib_list )

{

//保存了加载的opengl相关的so导出接口，egl接口

egl_connection_t * cnx = NULL ;

egl_display_ptr dp = validate_display_connection ( dpy , cnx );

//可以想象一下就是吧window包装成一个EGlSurface, cnx -> egl是so提供的一系类函数指针

EGLSurface surface = cnx -> egl . eglCreateWindowSurface ( iDpy , config , window , attrib_list );

}

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