SPDX standardizes how source code conveys its copyright and licensing information. See https://spdx.github.io/spdx-spec/1-rationale/ . SPDX tags are adopted in many large projects, including things like the Linux kernel.
We need this because we need to pass the layer to MoltenVK, not the view handle. But the input subsystem still needs the window.
And the associated GLContext bits
