关于5.1 surfaceflinger最后一步postFB到显示的问题

[u013266076]

我是想在 像素没进显示之前，把像素数组给修改了
查了一些资料 说实在 surfaceflinger 的postFramebuffer 里面。

void SurfaceFlinger::postFramebuffer()
{
    ATRACE_CALL();

    const nsecs_t now = systemTime();
    mDebugInSwapBuffers = now;

    HWComposer& hwc(getHwComposer());
    if (hwc.initCheck() == NO_ERROR) {
        if (!hwc.supportsFramebufferTarget()) {
            // EGL spec says:
            //   "surface must be bound to the calling thread's current context,
            //    for the current rendering API."
            getDefaultDisplayDevice()->makeCurrent(mEGLDisplay, mEGLContext);
        }
        hwc.commit();
    }

    // make the default display current because the VirtualDisplayDevice code cannot
    // deal with dequeueBuffer() being called outside of the composition loop; however
    // the code below can call glFlush() which is allowed (and does in some case) call
    // dequeueBuffer().
    getDefaultDisplayDevice()->makeCurrent(mEGLDisplay, mEGLContext);

    for (size_t dpy=0 ; dpy<mDisplays.size() ; dpy++) {
        sp<const DisplayDevice> hw(mDisplays[dpy]);
#ifdef MTK_AOSP_ENHANCEMENT
        if (!hw->mustRecompose()) continue;
#endif
        const Vector< sp<Layer> >& currentLayers(hw->getVisibleLayersSortedByZ());
        hw->onSwapBuffersCompleted(hwc);
        const size_t count = currentLayers.size();
        int32_t id = hw->getHwcDisplayId();
        if (id >=0 && hwc.initCheck() == NO_ERROR) {
            HWComposer::LayerListIterator cur = hwc.begin(id);
            const HWComposer::LayerListIterator end = hwc.end(id);
             // 只有三帧
            	 ALOGI(" tyty-layout count = %8d",count);
            	//注释会出现黑屏
            	//一半的数据没丢进去也没有设置NULL，间歇性黑屏？好像是系统挂了
            	//cant connect activity manager
            	/*
            for (size_t i = 0; cur != end && i < count; ++i, ++cur) {
            	if(i < count/2)
            		{
            		currentLayers[i]->onLayerDisplayed(hw, &*cur);
                
            		}
            		else{
            		currentLayers[i]->onLayerDisplayed(hw, NULL);
                
            		}
                
            }*/
            
         
            for (size_t i = 0; cur != end && i < count; ++i, ++cur)
             {
             
             	currentLayers[i]->onLayerDisplayed(hw, &*cur);
            }
            
        } else {
            for (size_t i = 0; i < count; i++) {
                currentLayers[i]->onLayerDisplayed(hw, NULL);
                
            }
        }
        
    }

    mLastSwapBufferTime = systemTime() - now;
    mDebugInSwapBuffers = 0;

    uint32_t flipCount = getDefaultDisplayDevice()->getPageFlipCount();
    if (flipCount % LOG_FRAME_STATS_PERIOD == 0) {
        logFrameStats();
    }
}

而onLayerDisplayed函数是这样的

 virtual void onDisplayed() {
        hwc_region_t& visibleRegion = getLayer()->visibleRegionScreen;
        
        //把 bufferfromdata 修改
        SharedBuffer const* sb = SharedBuffer::bufferFromData(visibleRegion.rects);
        	
        if (sb) {
            sb->release();
            // not technically needed but safer
            visibleRegion.numRects = 0;	
            visibleRegion.rects = NULL;
        }

        getLayer()->acquireFenceFd = -1;
    }

那个getLayer() 又是一个模板类的一个函数，然后 我就不知道 visibleRegion.rects 是个什么了？
求相关大神指点。实在postFramebuffer里面修改吗？ 怎么才能拿到像素数据？