This started as a C++ wrapper around Apple's Metal API, but then I wanted to expand it to also use OpenGL as a backend to compile the same application on other platforms with (preferably) no code changes.
NOTE: The OpenGL backend is not complete.
I've included some examples to show usage. The hello_metal example must use the Xcode generator in order to compile the metal shaders. The hello_macgl example uses a NSOpenGLView for rendering, as glfw3 does not seem to create a view capable of rendering OpenGL on macOS mojave.