ShivaVG looks definitely as a way to ease the pain of porting to OpenGL.�
Some notes on the matter. The Cairo backend for OpenGL is opengl but yet its not opengl. �What it does is render cairo as a opengl texture. OpenGL true power is in the shaders so you dont get the kind of hardware acceleration you would expect.�
Speewise as surprising this may sound �opengl is not the ideal option, because opengl is mainly 3d orientated. The ideal solution from what I have seen would be something like CUDA or OpenCL, that give direct access to the GPU cores and allow you to do any kind of computation thus liberation from the restrictions of APIs. For example Blender takes advantage of both Opengl and CUDA , the CUDA renderer is phenomenal better because of its flexibility.�
The problem however is that all that are very technical and it takes quite some dedication to implement.�
A reason why I abandoned opengl as an idea is that I came to realise that Cairo was already fast enough for my needs. But I still keep that door open for the distant future, ShivaVG with OpenCL would be awesome for really intensive GUIs and complex Graphics and definitely would love to give it another try eventually. ��