In Stretchy Thumbs, Casey Liss wonders if the new system wide back gesture in iOS 7 (obviating the need to constantly reach to the top left of the screen) is a step towards supporting the idea of a larger screened iPhone Plus. I would say that in most of the new patterns in iOS 7, Apple are telegraphing much more than that: clear steps towards proper resolution independence for iOS.
These changes would pave the way not for an iPhone Plus with bigger pixels, but one with a new screen resolution at current Retina iPhone DPI levels that can display more content on screen. And once resolution independence is established, who knows what other larger or smaller devices it would pave the way for?
The first thing to consider is the removal of not just most, but all visual ornamentation. As I noted in my previous post, this is a little bit like the transition from sprite to polygon based videogames. In that world too, moving to polygon based graphics also provided resolution independence.
As long as your textures can be stretched easily (hello simple gradients and flat translucency) you can scale the underlying shapes freely and maintain sharpness and pixel perfect visual accuracy. In contrast, in iOS 6 world, almost every asset has pixel level graphical treatments: drop shadows and glows that scale horribly and need to be re-drawn and pixel-fitted to support resolutions that aren't simple divisors or multiples of the original.
Secondly, iOS 7 takes a giant step towards layouts that aren't strongly tied to precise pixel positions. The move towards more dynamic physics based layouts encourages designs that are a result of interactions between objects, springs and layers rather than pixel perfect placement.
I completely agree with Rene Ritchie over at iMore when he says:
Where everything in iPhone OS 1 to iOS 6 looked rendered, everything on iOS 7 looks on-the-fly. Animation, interaction, color, type, control, everything.
In addition, Apple has been encouraging developers to use auto layout for some time now. It's not out of the question that at some point in the future a new device might only natively support apps created with auto layout, with older apps constrained to appearing in an iPhone-apps-on-iPad style frame. Auto layout makes layouts more fluid and based on relative placements -- the resultant apps could theoretically scale well and stay looking good.
Thirdly, there are already a number of areas in iOS 7 where views are rendered independently or only loosely coupled to the viewport. The new multitasking interface is a great example of this:
The app snapshots aren't exactly half the size of the full screen (they're slightly smaller) and the left-right scrolling is fluid. When the user lifts their finger, the list floats to a natural stop with an item centred. All of these things are compatible with both an arbitrary viewport and aspect ratio -- this view could easily adapt to changes in either.
The Phone app's interface shown above displays similar traits. The simple circular buttons, the full width flat colour Call button -- both could easily be scaled or laid out in a different space and remain perfectly rendered.
You can see this sort of thinking throughout Apple's other stock apps too. The new Safari is good example of another UI amenable to arbitrary scaling -- every element is either centred or anchored to a corner and there are no visual effects that aren't simple to scale (from the line-drawn buttons to the trapezoidal tab previews).
Finally, there's the new TypeKit typography rendering engine (more here). A key part of this is Dynamic Type -- the engine knows how to scale fonts such that the weight dynamically adjusts as the size changes. iOS 7 uses this most obviously to power an accessibility slider that allows users to adjust the base OS text size manually across the board, and see this reflected in all apps that support it. It's only a short leap to imagine this engine also being used to scale type for a variety of different screen resolutions. The deliberate decision to move from icons to (dynamically sized) text for a lot of controls will also enable those apps to scale easily with minimal rework.
A disproportionate amount of what's been written about iOS 7 since the reveal at WWDC has focused on relatively trivial details such as the aesthetic qualities of the new app icons. Almost no one has stepped back and looked at what the collection of changes mean when taken as a whole. Once you do that and consider TypeKit, UIKit Dynamics, the new gestures, the continual pushing of auto layout and the wholesale removal of ornamentation the clues become too obvious to ignore. It was inevitable that Apple was going to have to move iOS towards resolution independence but I think it's now pretty clear how they're going to do it too.