You already told me what the patent was. I saw it. No part of it resembles an invention in any way. It's vague enough that anything that sends content to a display will inherently violate it. Google argued it's not valid because it's not a fucking invention and has literally nothing in common with one. It's the exact same horseshit as "a shopping cart, but online" or "volume control multiple devices, but online". Almost no software can possibly justify a patent being awarded and this is an especially offensive example of it.
ARM designed a complex instruction set and explicit hardware implementations. That't not the same as owning trivial features.
"Rounded corners" is one small element of a design patent. Design patents are an entirely different, unrelated category not connected to utility patents at all and only protect against companies deliberately ripping off your entire package of branding choices. That's not the same as pretending you can own a very basic idea that thousands of people had before you did.
Utility patents for basic software features are fundamentally broken and massively detrimental to society. If the actually innovative algorithms over time had been patented and enforced, we probably wouldn't even have an OS yet, let alone the rich ecosystem modern software is, all built on the fact that you don't own basic features, only the code of your specific implementation of it.