Apple is planning to add a split-screen multitasking mode to its iPads in iOS 8, according to "sources with knowledge of the enhancement in development" speaking to 9to5Mac . The feature will supposedly allow two applications to run side-by-side while the tablet is in landscape mode, not unlike the similar Snap feature in Windows 8.1 or the multi-window mode supported on many of Samsung's phones and tablets . iPad applications have always used the tablet's entire screen, which keeps things simple but can feel restrictive for heavy multitaskers.

Though 9to5Mac's sources have been accurate in the past, as with all rumors, this report should be taken with a continuous stream of salt until you actually see Apple get up on stage and announce it. If it's true, this new display mode implies big changes to the way that iPad apps are designed and the way that they interact with each other, and we wanted to take a look at the hurdles in iOS and the iPad hardware that would have to be dealt with to make this feature a reality. We'll also be making some informed guesses about how Apple might jump over them.

Resolution independence

Making a split-screen iPad UI wouldn't be as simple as plopping two app windows next to each other and shrinking them down to fit on the display. To be consistent with Apple's other guidelines—the ones about minimum sizes for buttons and other tappable elements, for example—applications are going to need to be redesigned to support split-screen mode.

Android and Windows 8 (and apps built for those platforms) already expect to encounter a wide variety of screen sizes, resolutions, and pixel densities. This makes those applications more elastic and better able to expand and contract to fill the available space, whether they're given 25, 50, 75, or 100 percent of the screen to work with. Current iOS apps, on the other hand, only need to support four different configurations in iOS 7: iPhone 4-style screens, iPhone 5-style screens, non-Retina iPad screens, and Retina iPad screens.

Adding a split-screen mode is either going to increase the types of "screens" developers will need to support—you'd at least need to add 50-percent-split designs to the existing full-screen designs, with more views added if 25- and 75-percent splits are also available—or it's going to necessitate better support for multiple resolutions. Given the rumors that the next iPhone will have a larger, higher-resolution screen than the current iPhone 5S, it seems like the right time to make iOS and its apps resolution independent.

Apple has introduced some developer features like Auto Layout that will help this potential project along (and others have written about the progress iOS 7 made toward resolution independence). Auto Layout makes applications more dynamic—instead of saying "I want UI element X to be 100 by 200 points wide and for it to be positioned here" you'd say "I want UI element X to be positioned 20 points from the top of the screen, and there should always be 20 points of padding between it and element Y." There's a nice rundown of the feature here.

This will, in theory, allow an application to display properly and look consistent on a screen being viewed in either portrait or landscape mode (or, in theory, on both an 1136×640 iPhone 5S screen and some hypothetical future 1080p iPhone screen). That's a good start, but remember that Auto Layout was only introduced in iOS 6—there are still going to be plenty of developers who aren't using it—up until now, they've been able to target a handful of exact screen sizes without problems. This is probably the biggest problem to overcome from a software design standpoint.

A more porous sandbox

iOS power users have long wanted third-party applications to be more capable—we want our apps to be able to do more things, and we want them to be able to communicate more directly with one another rather than through the half-measure that is the "share" button. The report says that the split-screen display mode "is designed to allow for apps to more easily interact... for example, a user may be able to drag content, such as text, video, or images, from one app to another." This is going to require applications that can talk to each other more freely.

Another rumor dump (also by 9to5Mac) suggested that Apple would introduce an "XPC" service to iOS that would facilitate communication between applications. The description makes it sound comparable to Android's Intents system—if application A tells the operating system "yes, I can upload photos," application B will be told about it if it tells the OS it wants to upload a photo.

iOS apps have historically been cordoned off from one another in the name of security, but a system like this one would make applications more capable without completely compromising them. An "XPC" system would be more permissive than what Apple allows now, but it would still only allow applications to interact with one another in certain well-defined ways. As for the split-screen feature itself, dragging content between one window and another sounds like a fancy way to copy and paste—something that iOS can already do.

More memory

Another hurdle is hardware. iPads have generally shipped with about half the RAM of contemporary Android and Windows tablets. Their restricted multitasking model is one of the reasons why—users are typically only interacting directly with one application at a time, and other apps can be suspended to RAM and reloaded as the operating system needs more resources. Background applications are limited in what they can do (and when they can do it) by the Background App Refresh service.

What happens if, all of a sudden, you have two applications that now need to be active simultaneously, fighting for the same pool of RAM and CPU time? Does battery life take a hit? What happens in the future when those applications go 64-bit to take advantage of the A7, but need to use more RAM as a result?

At least on iPads with 1GB of RAM, hardware limitations might not be a huge roadblock. It's kind of interesting to hook an iPad up to Xcode, fire up the Activity monitor, and watch just how aggressive Apple's memory management is—the above screenshot is from a fourth-generation iPad running iOS 7.1.1. The biggest memory hog on any system is a browser with a bunch of tabs open, but iOS appears to limit the amount of active RAM that Safari can consume to just above 200MB (open more tabs and the virtual memory usage will continue to climb while active memory use stays about the same). Other applications are ejected from memory aggressively, and Springboard and other system services and background tasks only need a couple hundred megabytes of active memory altogether.

Enabling multitasking on an iPad with 1GB of RAM might suspend other applications from memory more aggressively, which may cause more delays if you switch between many different applications rapidly. It's also a safe bet that older iPads like the iPad 2 and iPad mini wouldn't be able to handle the multitasking feature. Newer ones with reasonably fast CPUs and 1GB of RAM should be fine.

Of course, Apple could do what it has done before: restrict the hardware that can use the split-screen multitasking feature. It could choose to support the feature only on some brand-new iPad with a beefier CPU and 2GB of RAM instead of 1GB. This might limit developer support for the feature, at least initially—devs won't want to spend a lot of time on a feature that appeals to just a sliver of the user base. But it would skirt any problems related to hardware restrictions, and Apple has certainly introduced exclusive features with new devices before (see Touch ID and Siri, though third parties didn't need to do any work to support either of those since APIs weren't made available).

A split-screen display mode on the iPad is certainly possible, and the feature has been handled well by others—use Windows 8 on a tablet and you'll find that IM and e-mail clients, Twitter apps, word processors, and browser windows can all be useful even if confined to a quarter of the screen. Adding the feature would just require Apple and its developers to deal with a lot of challenges they haven't had to worry about before.

We're due to get our first look at iOS 8 at Apple's Worldwide Developers Conference in early June. If Apple is planning to bring this feature to iOS, we'll probably hear more about it then.