title: 2d drawing primitives and images: OpenGL, Cairo or Agg
body: <p>I'm making a game and thought about using vector shapes for the UI. I want to know what the best renderer for this. I think Agg is faster than Cairo, but Cairo can use hardware acceleration if it's available. And how about opengl? Is a good idea I use gl textures for images and lines to do rectangles, rounded rectagles and circles? Or is better I render cairo surfaces in opengl?
  Other alternatives I found are Google Skia and SFML. What do you think of Skia? The SFML also draws polygons. I can make rounded shapes using polygons. I'm even thinking of using SDL or SFML to control events. In both I can create an OpenGL context and I've gotten used to their roles in control of events, which are crossplatforms.
  I want a cross-platform solution. It should work in linux, mac and windows.</p>