This method retrieves a back buffer from the device's swap chain.
HRESULT GetBackBuffer( UINT BackBuffer, D3DMBACKBUFFER_TYPE Type, IDirect3DMobileSurface** ppBackBuffer );
[in] Index of the back buffer object to return. Back buffers are numbered from 0 to the total number of back buffers - 1. A value of 0 returns the first back buffer, not the front buffer. The front buffer is not accessible through this method. If BackBuffer exceeds or equals the total number of back buffers, the method fails with D3DMERR_INVALIDCALL.
[in] A D3DMBACKBUFFER_TYPE value.
[out] Address of a pointer to an IDirect3DMobileSurface interface that represents the returned back buffer surface.
Calling this method will increase the internal reference count on the IDirect3DMobileSurface interface. Failure to call IUnknown::Release when finished using this IDirect3DMobileSurface interface results in a memory leak.