Huh, it's more than just a rendering API: "can render to windows using an OS-native graphics pipeline and provides a browser-like UI event framework". They could add wgpu to get WebGPU support and ANGLE to get WebGL support.
Skia is a widely used library (off the top of my head, Chrome, Firefox, and LibreOffice use it) that supports lots of rendering targets, including WebGPU and ANGLE.
I don't mean WebGPU and WebGL as Skia backends. I mean WebGPU and WebGL as APIs that this library could expose to users in addition to the HTML canvas API.
That's very similar to what Qt already provides (QPainter, for raw image/windows, more sophisticated widgets with event support. Further- and this is something I've been looking for a while- they have a graphicsview that allows resolution-independent rendering of millions of objects, with events, in an larger-than-window graphics plane.