Demonstration of alpha blended compositing of opengl contexts via borderless windows using the Win32 API
Based on https://github.com/rossy/borderless-window and https://github.com/ocornut/imgui .
The application only creates an OpenGL 2 context, because creating a modern context is a PITA and out of scope here.