It seems to me that from a UI perspective, the problem of multitasking in iPhone OS has already been solved. Both Safari and the Springboard (Home) app have the ability to slide from window to window, or screen to screen. A similar solution could be used to switch between running applications. Let’s call it ‘App Switching Mode.’

The only major UI detail to sort out is how to enter App Switching Mode. Presumably it would be triggered by some touch gesture. For example, perhaps you could hold the home button while swiping left or right on the screen. What the exact gesture might be is anyone’s guess; for the purposes of this proposal let’s just call it the ‘App Switching Gesture.’

Performing the App Switching Gesture would shrink the current app screen down, revealing the screens of other running apps on the left and right. Then you’d use the familiar left and right swipes to move from app to app, and then tap an app to bring it forward. Like I said, very similar to pages in Safari.

See it in action

Here’s a quick demo I put together with the helpful magic of jQuery. Since it’s a pain to imitate multitouch gestures in Javascript, I just created buttons as stand-ins. Click ‘App Switching Gesture’ to see the demo, then click ‘Swipe Left’ or ‘Swipe Right’ to move from screen to screen. Then tap an app to bring it forward. (I only tested this demo in Safari and Firefox, so I make no guarantees that it will work in other browsers.)

Clicking the ‘x’ on an app would close that app, just as pressing the home button does currently. Switching to the Home app would allow you to launch any other app, which would then show up as another screen in the app switcher. If you launch an app that’s already running, it would just switch to that app rather than spawn a new process, similar to Spaces on Mac OS X. In fact this whole concept is similar to Spaces, except that there is only one app per space, and only one space per app.

One nice thing about this solution is that it wouldn’t require users to change their existing behavior whatsoever. They can click the home button and use the Springboard app as a rudimentary app switcher, just as we all currently do.

One thing this demo does not address is how to limit the number of running applications. (If Apple ever implements multitasking on the iPhone, I assume they’ll still place a limit on the number of running apps, similar to the limit of 8 pages open in Safari.) Say they set the limit at 8 running applications. What happens when you try to launch a ninth? That’s a bit of a stumper. Hopefully they’re working on it.

One thing that might help solve that problem is a more robust notifications framework. Hopefully they’re working on that too.

Obviously there are some technical hurdles, specifically CPU usage and battery life, that make multitasking on the current iPhone impractical. Presumably those issues will be mitigated with time. But it may also be the case that Apple doesn’t feel that the convenience that multitasking provides would outweigh the UI complexities that accompany it. The iPad, which has a killer CPU and great battery life, doesn’t have multitasking either — which may be an indicator that Apple doesn’t plan to implement multitasking even when CPU usage and battery life aren’t an issue. I hope I’m wrong on that count.

Traditionally, making power user features accessible to regular users has been one of Apple’s fortés, and they’ve usually managed to do so while still maintaining the flexibility that power users require. With Spaces, however they’ve fallen short of that mark. It’s a new feature, so hopefully they’ll improve it with future updates. Here’s one way I think they could improve it dramatically.

The above screenshot shows the Spaces prefpane with one simple addition: a checkbox, selected by default, which reads “Switch Spaces automatically.” With this checkbox on, Spaces would behave as it currently does, automatically switching Spaces when you switch to an app whose frontmost window is hidden in another space. (Perhaps they could smarten it up a bit so it wouldn’t automatically switch if the given app already has a window open in the current space, but I digress.)

With this checkbox off, Spaces would never switch spaces for you. Instead you would stay in the current space until you decide to switch spaces yourself, either by invoking the meta-view and clicking another space, or by using the modifier keys defined in the Spaces prefpane.

So suppose you’re in space 3 and all your currently-open Safari windows are in space 1. If you switch to Safari, it would act as if there were no windows open and open a new one for you. So each space is truely like a new monitor, a new workspace, oblivious of its partners.

Let’s follow this through a bit more. There are certain window types that you’d want to have available in every space. For example, Safari’s Preferences window, or its Downloads window, or Mail’s Activity window. These would be useful to have in every space. But what if Safari’s Downloads window is already open in space 1, and you press Command-Option-L while in space 3? With auto-switching off, invoking any window that is already open in another space would bring it to you in the current space, rather than swooping you over to it. So if you’re in space 3 and you want to look at that Ebay auction item that’s open in some other space, you could choose the window from Safari’s Windows menu, or from Safari’s Dock menu, and it would swoop into view in your current space, keeping you in place, not disrupting your workflow or your context.

I think this simple change would go a long way toward making Spaces work for the power users who are most likely to get the most use out of it, while still keeping it simple and accessible for folks like my dear old Mom.

[Hat tip to @philoye for thinking this through with me.]

[Digg this story]

The current state of affairs is clearly an unfinished work. I feel pretty certain that Apple will issue an iPhone update (perhaps as part of firmware 1.1.2 that is rumored to be coming soon) which will include a new To Do iPhone application to accompany the Notes application that shipped with the iPhone. The new firmware will also update the iPhone mail client so it won’t display the Apple Mail To Do folder created by Mail.app. Instead, it will use this folder (behind the scenes) to serve as a conduit for syncing To Do’s between the iPhone and Mail.app on the desktop. My hope is that they’ll also bring Notes syncing along for the ride.

I’m not sure how Apple might carry this functionality over to iPhone owners who use Windows — or those who use pre-Leopard versions of Mac OS X, for that matter. Perhaps Apple will tout To Do and Notes syncing as a Leopard-only feature.