這里LayerBuffer的創(chuàng)建是在SurfaceFlinger中由SurfaceFlinger的友員類BClient調(diào)用createSurface函數(shù)new出LayBuffer對象。
數(shù)據(jù)流向過程，以opencore解碼舉例：opencore中調(diào)用ISuface的postBuff，實際ISurface的繼承類BpSurface中的postBuffer被調(diào)用，通過Binder機制向同樣是ISurface的繼承類的BnSurface請求服務(wù)（通過發(fā)送POST_BUFFER命令）：
virtual void BpSurface ::postBuffer(ssize_t offset)
{
……………………………………………….
remote()->transact(POST_BUFFER, data, &reply, IBinder::FLAG_ONEWAY);
}
BnSurface響應(yīng)相應(yīng)命令，同樣調(diào)用postBuffer函數(shù)：
case POST_BUFFER: {
…………………………….
postBuffer(offset);
…………………………….
}
實際將會調(diào)用BnSurface的繼承類Surface的postBuffer函數(shù)(class Surface : public BnSurface)，Surface是LayBaseClient的嵌入類，而Surface類的postBuffer函數(shù)未實現(xiàn)，這會導(dǎo)致最終調(diào)用Surface類的繼承類SurfaceBuffer的postBuffer函數(shù)(class SurfaceBuffer : public LayerBaseClient::Surface):
void LayerBuffer::SurfaceBuffer::postBuffer(ssize_t offset)
{
……………………………………………..
owner->postBuffer(offset);
}
SurfaceBuffer類是LayBaseClient的繼承類LayerBuffer的嵌入類，SurfaceBuffer的postBuffer最終會調(diào)用LayerBuffer的postBuffer函數(shù):
void LayerBuffer::postBuffer(ssize_t offset)
{
…………………………………………….
sp<Buffer> buffer;
if (heap != 0) {
buffer = new Buffer(heap, offset, w, h, hs, vs, f);
if (buffer->getStatus() != NO_ERROR)
buffer.clear();
setBuffer(buffer); //這個函數(shù)將會置mBuffer指針
invalidate();
}
}
在此函數(shù)中將會創(chuàng)建Buffer類用來存儲數(shù)據(jù)，LayerBuffer類中的mBuffer指針會指向這個數(shù)據(jù)區(qū)由BClient利用。
另一方面，關(guān)于LayerBuffer類的創(chuàng)建。 在Java層，我們調(diào)用Surface_init函數(shù)之后，會對應(yīng)于android_view_Surface.cpp函數(shù)中的Surface_init函數(shù)，此函數(shù)會調(diào)用SurfaceComposerClient類的createSurface函數(shù)，
sp<Surface> SurfaceComposerClient::createSurface(
int pid,
DisplayID display,
uint32_t w,
uint32_t h,
PixelFormat format,
uint32_t flags)
{
……………………………………………..
sp<ISurface> surface = mClient->createSurface(&data, pid,
display, w, h, format, flags);
if (surface != 0) {
if (uint32_t(data.token) < NUM_LAYERS_MAX) {
result = new Surface(this, surface, data, w, h, format, flags);
}
}
……………………………………………..
}
紅色代碼行將會調(diào)用BpSurfaceFlingerClient類的CreateSurface函數(shù)（mClient是BpSurfaceFlingerClient類指針）同樣使用Binder機制向BnSurfaceFlingerClient類請求服務(wù)（通過發(fā)送命令CREATE_SURFACE）：
virtual sp<ISurface> createSurface( surface_data_t* params,
int pid,
DisplayID display,
uint32_t w,
uint32_t h,
PixelFormat format,
uint32_t flags)
{
………………………………………..
remote()->transact(CREATE_SURFACE, data, &reply);
………………………………………..
}
BnSurfaceFlingerClient對CREATE_SURFACE的相應(yīng)將同樣調(diào)用CreateSurface函數(shù)。但此函數(shù)在這個類中未實現(xiàn)。
case CREATE_SURFACE: {
……………………………………………..
sp<ISurface> s = createSurface(¶ms, pid, display, w, h, format, flags);
………………………………………………..
}
因此這個函數(shù)會由其繼承類BClient來調(diào)用，BClient類調(diào)用CreateSurface時會導(dǎo)致其友員類 SurfaceFlinger類的createSurface函數(shù)被調(diào)用而new出LayerBuffer的對象：
sp<ISurface> BClient::createSurface(
ISurfaceFlingerClient::surface_data_t* params, int pid,
DisplayID display, uint32_t w, uint32_t h, PixelFormat format,
uint32_t flags)
{
//BClient類的調(diào)用會調(diào)用SurfaceFlinger類的createSurface
return mFlinger->createSurface(mId, pid, params, display, w, h, format, flags); //這里從JAVA層來看，將會完成對LayerBuffer對象的創(chuàng)建，這個對象是圖像合成的關(guān)鍵。
}
sp<ISurface> SurfaceFlinger::createSurface(ClientID clientId, int pid,
ISurfaceFlingerClient::surface_data_t* params,
DisplayID d, uint32_t w, uint32_t h, PixelFormat format,
uint32_t flags)
{
……………………………………………….
switch (flags & eFXSurfaceMask) {
case eFXSurfaceNormal:
if (UNLIKELY(flags & ePushBuffers)) {
layer = createPushBuffersSurfaceLocked(c, d, id, w, h, flags); //這個函數(shù)會new出LayerBuffer對象
} else {
layer = createNormalSurfaceLocked(c, d, id, w, h, format, flags); //Layer對象
}
break;
case eFXSurfaceBlur:
layer = createBlurSurfaceLocked(c, d, id, w, h, flags); //LayerBlur對象
break;
case eFXSurfaceDim:
layer = createDimSurfaceLocked(c, d, id, w, h, flags); //LayerDim對象
break;
}
…………………………………………..
}
在這里我們開始進入SurfaceFlinger的服務(wù)。
注意： 關(guān)于SurfaceComposerClient類的作用，它是用來產(chǎn)生Binder機制的，舉例：
status_t SurfaceComposerClient::freezeDisplay(DisplayID dpy, uint32_t flags)
{
const sp<ISurfaceComposer>& sm(_get_surface_manager());
return sm->freezeDisplay(dpy, flags);
}
const sp<ISurfaceComposer>& _get_surface_manager()
{
if (gSurfaceManager != 0) {
return gSurfaceManager;
}
sp<IBinder> binder;
sp<IServiceManager> sm = defaultServiceManager();
do {
binder = sm->getService(String16("SurfaceFlinger"));
if (binder == 0) {
LOGW("SurfaceFlinger not published, waiting...");
usleep(500000); // 0.5 s
}
} while(binder == 0);
sp<ISurfaceComposer> sc(interface_cast<ISurfaceComposer>(binder));
Mutex::Autolock _l(gLock);
if (gSurfaceManager == 0) {
gSurfaceManager = sc;
}
return gSurfaceManager;
}
這是一個全局函數(shù)，我們在Binder機制中說明過，這個函數(shù)的作用就是用來生成繼承自
ISurfaceComposer的BpSurfaceComposer繼承類對象。使得return sm->freezeDisplay(dpy, flags);調(diào)用的是BpSurfaceComposer類的函數(shù)。
SurfaceComposerClient另一個作用，它還可以調(diào)用BpSurfaceFlingerClient類的相應(yīng)函數(shù)，同時也可以設(shè)置其他類的類成員，也就是說它是一個對外的總接口。
這里先寫到這兒，Surfaceflinger也是非常復(fù)雜，我的工作筆記還有一半多的內(nèi)容，在貼完工作筆記后，我會給出一個總結(jié)來理順大家的思路！??！
