Android Graphics 2

1 Surface Structure

This figure is based on froyo, and does not give detail about synchronization between Client and Server.
ISurface provide RPC interface between Client and Server.
GraphicBuffer encapsulate the memory shared by Client and Server
Surface in Client part transform the request for the upper framework and application to the Server Part Object SurfaceLayer.
SurfaceLayer in Server part will actually handle the request.

For ISurface,
It provide two group interface, one for SurfaceLayer, the other is used for SurfaceLayerBuffer.
SurfaceLayer means the memory for Surface is allocated in Server part, While SurfaceLayerBuffer means memory for Surface is transferred from the client.

For Surface:
For Surface, there exists two GraphicBuffer object, backBuffer for drawing and frontBuffer for displaying. The following invocation sequence display the first time to invoke Surface.lock function to get the addr of graphics memory

2 Surface Flinger

the main work of SurfaceFlinger is compose dirtry region of all layer to the backBuffer of current framebuffer, and then flip this backBuffer to display.

(I got this image from the web, thanks to the writer :) ) 

The following invocation sequence give more detail.

handlePageFlip;
In this function, SurfaceFlinger will invoke lockPageFlip of every Layer.
lockPageFlip is a very import function for Layer, it will create texture object used by Opengl library to do the composition, more details will be discripted in other document

if any layer need recomputeVisibleRegions, computeVisibleRegions will be invoked to re-compute every layer’s visible region on the framebuffer. this is a complex algorithm

ComposeSurface
general it will invoke draw function of every layer with the its visible region as parameter in Z-order

postFramebuffer
invoke eglSwapBuffers to display the final framebuffer

3 Gralloc&CopyBit

gralloc encapsulate the memory and framebuffer operation

GraphicsBuffer, GraphicsBufferMapper and GraphicBufferAllocator encapsulate memory operation of gralloc module.

These three class will help system to allocate graphics memory and map the shared graphics memory to the App process space. 

For framebuffer operation, it is related to FramebufferNativeWindow and DisplayHardware

copyBits module has be removed from 2.3 or 3.0 version,

and it mainly defined the following interface
int blit_copybit(
struct copybit_device_t *dev,
struct copybit_image_t const *dst,
struct copybit_image_t const *src,
struct copybit_region_t const *region)

int stretch_copybit(
struct copybit_device_t *dev,
struct copybit_image_t const *dst,
struct copybit_image_t const *src,
struct copybit_rect_t const *dst_rect,
struct copybit_rect_t const *src_rect,
struct copybit_region_t const *region) 

copyBits module is mainly used in andord software EGL/Opengl ES impl,

blit_copybit is mainly used in software EGL/Opengl ES eglSwapBuffers impl to copy minimum unchanged range from front buffer to back buffer. and blit_copybit does not take alpha into consideration .

stretch_copybit is mainly used software EGL/Opengl ES impl to draw Texture on the draw surface, It need take alpha value into consideration.