When you're calling any library, that simple C call invariably goes somewhere else inside the library itself. For OpenGL this is because there's always hooks for introspection, or because the GPU driver wants to implement something themselves, etc. For many other libraries it's just because people don't feel like they've written "production quality code" unless it goes through a bunch of hoops and ends up in some method with five underscores in the name.
In Metal the Obj-C abstraction is part of the design and used to eliminate any other abstraction people would want to introduce. The objects you get back from the API are implemented straight in the GPU vendor code, and the debug tools can swap the methods out for extra validation, recording, etc.
In Metal the Obj-C abstraction is part of the design and used to eliminate any other abstraction people would want to introduce. The objects you get back from the API are implemented straight in the GPU vendor code, and the debug tools can swap the methods out for extra validation, recording, etc.