One rumoured feature for the upcoming iPhone is that it may feature a larger, 4″ screen (compared with the current 3.5″ screen). This, in turn, as has raised a question: will this impact developers? The answer, as always, is “it depends”.
The potential impact depends on whether the screen ratio changes along with the size. Right now, the iPhone screen is 960×640, which doubled the length and width dimensions of the original iPhone (which was 480×320). If the new screen maintains this same 3:2 ratio, then for the vast majority of iPhone apps, it shouldn’t matter. If the ratio moves away from 3:2 height to width, then this could present some short-term challenges.
Points, Not Pixels
Maintaining the same relative ratio is not a problem for most iPhone apps, in part because many of them don’t work in absolute pixels, they work in “points”. This allowed apps built for the original 480×320 format to work without modification, simply because now a “point” represents a 2×2 pixel square on the retina displays. The relative size of screen objects, and their distances, didn’t change. The absolute size did, but most apps didn’t work with absolute size. To be sure, there were exceptions. There were certainly developers that ignored Apple’s advice about working in “points” rather than in “pixels”. But those were more the exception than the rule.
Even for those apps that do deal with pixels, many also dealt with them in relative ways. Rather than putting some object “10 pixels from the left”, then put the object a some percentage of the width of the screen from the left side. If it truly had to be “10” on a retina display (and “5” on a non-retina display), they would typically detect landscape vs. portrait mode, and calculate accordingly. This provided protection against further changes in resolution.
Ratio Is Important, Not Dimensions
Getting back to the ratio, this is another key concept that minimized the impact when the retina display first came out. Again, the key for the iPhone and iPod Touch is the 3:2 height to width ratio when in portrait orientation. If the new display adds 10% in both width and height (so, let’s say it moved to 1056×704), it would still be 3:2, and the relative layout and dimensions would remain largely unchanged. For some apps, this may still be an issue (because some do hard-code the dimensions to detect what screen they are on, and adjust calculations accordingly). I won’t claim that there will be zero impact. But for apps that use standard controls, and aren’t messing about with screen dimensions, the change should be transparent.
But If the Ratio Changes…
If the ratio of the new screen is different, then it is a different story. What I would expect is that apps that aren’t enabled for the new resolution (using through the properties of the app, developers will know the plist file I’m talking about), then I would expect that the new device will use some kind of letterboxing to present the app with the same size and screen ratio, with black bands in place of the unused pixels.
It does mean that app developers would need to add a new screen dimension and new layout files for the interfaces. It would be similar to when the iPad came out, which not only had new dimensions, but a different screen ratio (2048×1536 pixels, or 4:3). On the iPad, iPhone apps run in an emulator, which puts an iPhone screen in the middle of the iPad screen, and offers a 2x magnification option. But an app required a new layout (and an indication of use of the iPad screen size for layout) to take full advantage of the new screen. It is likely that a new iPhone screen, with a different pixel ratio, will add a 3rd layout specification.
Adding a new layout isn’t necessarily a big deal for most apps, but for some of the more complicated apps with a lot of screens, it does mean work. It isn’t necessarily trivial, and it certainly can be tedious. I have some apps I’ve finished (or that I’m working on) that have half-dozen different screen layouts. Having to reconstruct that isn’t hard. But it is a bit tiresome, and obviously there are opportunities for mistakes. A potentially bigger deal is whether this larger iPhone screen is still treated like an iPhone, or if it will be treated more as an iPad (so things like popovers and splitviews could be part of the equation). Worse, it could be some weird hybrid, where it may offer some iPad features (like popovers) but not all of them (like no splitviews). This not only means new layouts, but it means the potential to revisit the user workflow within the app (adding more work and more testing). The hope would be that a bigger screen with a different ratio would not change other aspects of the iPhone user experience, and that developers and designers can treat it as nearly the same as the current iPhone, just with a different screen resolution and dimensional ratio.
If I Were To Bet…
If I were to bet, I would guess that a newer, bigger screen, maintains the same screen ratio, and possibly even the same pixel dimensions. What we’ll probably see is an iPhone with thinner bezels (to keep the size of the device about the same), and a screen that goes closer, and possibly right up to, the edge of the device itself. Sticking with the same relative screen dimensions should mean the smallest impact on the apps in the iTunes App Store, and not messing with that revenue source.