Most of these guidelines are exactly what you’d expect, but there are a few intriguing nuggets. For example, about the notch:
Don’t mask or call special attention to key display features. Don’t attempt to hide the device’s rounded corners, sensor housing, or indicator for accessing the Home screen by placing black bars at the top and bottom of the screen.
Apple wants developers to treat the display as though it were still a perfect rectangle, but to be mindful of the notch1 and rounded corners. They do advise developers not to place controls near the edges of the display, particularly at the very top and bottom; but, the display’s extremities are treated more like padding, which ought to give the display a more immersive experience.
This is very different from the way Apple has treated the OLED display in the Apple Watch, which is “designed to blur the boundaries between device and software”. Designers and developers are advised to use the full display, edge-to-edge, because the “Apple Watch bezel provides a natural visual padding around your content that eliminates the need for additional padding”. The iPhone X has a similar edge bezel; I’m curious about the choice not to embrace similar ideas. Perhaps it’s simply because iOS primarily uses white or near-white UI components — if that’s the case, will this change, maybe in iOS 12?
Don’t duplicate system-provided keyboard features. On iPhone X, the Emoji/Globe button and Dictation button automatically appear beneath the keyboard—even when using custom keyboards. Your app can’t affect these buttons, so avoid causing confusion by repeating them in your keyboard.
You can see this in action about a third of the way down the iOS on iPhone X page in the iMessage screenshot. The area around the keyboard switcher has long been cramped; this is a terrific refinement, and I’m glad to see Apple taking over the keyboard switcher functionality in third-party keyboards.
Update: Something to consider from Ian Parker’s 2014 interview with Jony Ive:
[…] He picked up his iPhone 6 and pressed the home button. “The whole of the display comes on,” he said. “That, to me, feels very, very old.” (The iPhone 6 reached stores two weeks later.) He went on to explain that an Apple Watch uses a new display technology whose blacks are blacker than those in an iPhone’s L.E.D. display. This makes it easier to mask the point where, beneath a glass surface, a display ends and its frame begins. An Apple Watch jellyfish swims in deep space, and becomes, Ive said, as much an attribute of the watch as an image. On a current iPhone screen, a jellyfish would be pinned against dark gray, and framed in black, and, Ive said, have “much less magic.”