Seems silly to have one set of API's for small touch devices and a completely different one for large mouse-driven devices. Shuts the door to large touch devices and small mouse-driven devices.
iPad Pro is already awkward. At that size, a mouse would be nice, along with lots of other desktop UX paradigms.
> What has Microsoft shown with their multi-paradigm direction?
Seems to be working. Windows Shell, modern Office, Edge, and Xbox dashboard are all using the same UI framework.
Since the introduction of iOS, Apple has seen a lot more growth and profits than Microsoft, and became the largest corporation in the world (by market cap).
I do think Microsoft's latest multi-paradigm devices (like Surface Pro), are gaining traction. But overall Apple has outpaced Microsoft while having different UI frameworks for mobile and PC.
Other criteria come pretty far behind that.
You'd be getting neither the benefits of native nor the benefits of cross-platform.
The differences between touch/mouse incarnations of basic components, such as lists, buttons, scrollviews etc. can often be resolved with adaptive design. Apple has already put the basics in place to allow for adaptive apps that scale from the smallest iPhone to the largest iPad. Doing the same for touch -> keyboard/mouse UI is not unthinkable.
I think the baseline toolkit could be the same, with some extra components for different form factors.
We're working on something like that (multi form factor UI toolkit) for Ubuntu, with Qt. Will see how far it goes.
No! No they absolutely don't!
Almost every Android app is clearly design for use on a touch device. Every aspect of the design is intended to be touch-first. That's totally fine – but the fact that they can be used with a mouse on a desktop does not mean that they work pretty well. The user interface paradigms are really very different.