This is great, but I don't see it being useful for most use cases.

Most high-level charting libraries already support downsampling. Rendering data that is not visible is a waste of CPU cycles anyway. This type of optimization is very common in 3D game engines.

Also, modern CPUs can handle rendering of even complex 2D graphs quite well. The insanely complex frontend stacks and libraries, a gazillion ads and trackers, etc., are a much larger overhead than rendering some interactive charts in a canvas.

I can see GPU rendering being useful for applications where real-time updates are critical, and you're showing dozens of them on screen at once, in e.g. live trading. But then again, such applications won't rely on browsers and web tech anyway.