The Cycles standalone GUI is a simple example of how to integrate interactive viewport rendering in an application. It uses SDL and OpenGL.

It could be improved in a few ways:

• Add text display support (requires a small embedded font + OpenGL shaders and vertex buffer setup)
• Alternatively, use a more complete GUI library like ImGUI. Needs to be decided if it's worth adding such a dependency for a simple example.
• Add OpenColorIO view transform support