On one side of the aisle, this fall will bring a new iPhone & iPad; on the other there’s a steady flow of Android handsets and tablets and in-betweens.

One thing about the Apple mobile line had been puzzling me till recently: There are only two form factors. The prognosticators think that the next iPhone will be about the same size and shape as it is now. The same is true of the iPad, except for maybe it’ll have a double-density “Retina” display.

It couldn’t be more different on the Android side, with devices of every size and shape imaginable, some of ’em real eye-rollers. Today, I laughed at a tweet from Sascha Segan: “Samsung now has: 2.8 3.2 3.5 3.7 4 4.3 4.5 5 7 7.7 8.9 10.1 inch screen Androids. Where's the 6-incher Sammy? Get on the case!” And Samsung is just one builder.

Theories of History · There are two possible explanations for this: First, Apple has ascertained that the 3½-inch and 10-inch diagonals constitute the Platonic ideals for screen size, and no others are worth building. Second, there are technical barriers to exploring new iOS form factors.

For a long time, I didn’t believe either theory. So when in 2010 I fell in love with the original Galaxy Tab, largely on account of its size, I confidently asserted “Apple will totally do a 7" device... This argument is over”. Clearly I’m eating those words.

John Gruber asserted repeatedly that a 7-inch (or other form factor) device was not in the cards because it would screw up the screen layouts; unless of course the new screen were an exact multiple of the number of pixels on its predecessor, as with the iPhone 4’s Retina Display.

Since I work on a daily basis with at least four different screen sizes, all of which are driven reliably by Apple software, this claim baffled me. Then I noticed that none of the iOS developers were pushing back; and also Gruber is always right when it comes to Apple whys and wherefores. (But these days, bizarrely bent out of shape on the subject of Google; every action is explained by some implausible combination of malice, hypocrisy, and intellectual-property knavery. Jeepers, John, unclench a bit. But I digress.)

I still didn’t really understand the technical issue.

The Real Reason · The scales fell from my eyes when I read Nick Farina’s An iOS Developer Takes on Android, which to my mind is the single best piece of comparative writing on this subject by anyone, anywhere. In particular, scroll down to the “A Real Box Model” section. (Hey Nick, real men put hashtags on their sections so people can link to them. That’s what hashtags are for, not the horrible things that Twitter and other miscreants are doing with them. But I digress.)

When I saw Nick’s sample iOS code, I initially shook my head in disbelief at all the little bits of hard-coded arithmetic, like y += 7 and MARGIN - 30. Clearly this logic is not resilient in the face of a different-shaped screen. But I bet it’s fast.

It’s not done that way in Android-land.

Android Assumptions · Just about the first one is that you have to deal with variations in shape, size, and density, but that you get lots of help from the framework. Check out Dianne Hackborn’s monumental New Tools For Managing Screen Sizes, a comprehensive introduction to screen geometries and the mighty “dp” unit that makes it all tractable. The repertoire of Layouts also helps, and is constantly being refreshed with things like ViewPager; which mostly Just Work in the face of any old set of screen dimensions.

It’s plausible, as Nick Farina implies, that iOS’ fixed-dimensions screen model is partly responsible for the astonishingly-fast performance Apple wrings out of the underlying hardware.

And I’m not even saying that Apple’s choice here is wrong. The trade-off, if I understand it correctly, is form-factor flexibility for performance and simplicity, and so far that’s been working out pretty well for them.

I Seem To Have Been Wrong · About Apple doing a 7-inch device, I mean. But I’m sure as anything that somebody is gonna sell a buttload of tablets at that size. I’ve got probably as much experience as anyone in the world carrying around large and small tablets simultaneously, and if I had to pick just one, it wouldn’t be ten inches in any dimension.


Comment feed for ongoing:Comments feed

From: Simon Wright (Sep 02 2011, at 01:10)

"real men put hashtags on their sections so people can link to them"

Perhaps the paragraph labelled "The Real Reason" isn't a section?!


From: Dave Walker (Sep 02 2011, at 02:18)

I think I may have mentioned this elsewhere, but my view is that devices around the 10" mark can be viewed as tablets, whereas anything smaller - if it doesn't also make 'phone calls - is a PDA.

For me, the critical thing about 10" is that this is pretty much the minimum size at which it's possible to get all 10 fingers on an adult-sized pair of hands down onto an on-screen keyboard, when the device is in landscape mode. This enables me to type at a pretty decent rate.

I actually do a fair amount of ad-hoc note-making on my iPad (I'm writing this comment on it); the main issue I have which prevents me writing longer comments on it, is its failure to handle scrolling within comment windows on a web page. The Notes app gets a lot of use, as does Mail.

Are users of smaller devices more comfortable typing one-handed, perhaps?


From: Ted Wise (Sep 02 2011, at 04:38)

I don't think Apple's approach has much to do with performance. I think it has everything to do with appearance. Apple seems to believe that in order to make excellent UIs you have to hand-tune them. Auto-layouts are thus anathema to them.


From: Andy Lee (Sep 02 2011, at 05:50)

>There are two possible explanations for this: First, Apple has ascertained that the 3½-inch and 10-inch diagonals constitute the Platonic ideals for screen size, and no others are worth building. Second, there are technical barriers to exploring new iOS form factors.

I think it's neither of these. Apple under Jobs 2.0 has always picked a small number of lines to draw in the sand. (I'm flailing for a better metaphor. Number of arrows behind which to put their wood?)

Look at the laptop market. Non-Mac laptops come in all the Apple sizes *plus* a whole bunch of other screen sizes. Meanwhile, Apple dropped their 12" PowerBook, much to the dismay of many users. It wasn't because OS X doesn't scale to 12". They just made a decision to prune it from their product line.

I do agree Apple's APIs for screen layout have long been overdue for an overhaul. Springs and struts served them well for a long time, but developers keep having to roll their own solutions to the limitations of that model.

Screen layout did get an overhaul with Lion and Xcode 4. My understanding is that it is a big improvement, though I don't know as much about it as I should.


From: Janne (Sep 02 2011, at 07:00)

A 10 inch tablet is 6-800 grams. That's too much weight to hold in one hand for longer periods.

A 10 inch tablet is also, well, 10 inches. Too large to hold in a crowded train without people bumping into it.

I agree on the 7 inches. And I think Google shot themselves in the foot to some extent by keeping the 3.x series closed and only releasing it for large, expensive high-end tablets. Let's hope Ice Cream Sandwich returns to the 2.x series trend of letting many manufacturers use it freely, in all kinds of formats and pricepoints.


From: Nelson (Sep 02 2011, at 07:41)

I think there's two things going on: a technical rendering constraint and marketing simplicity.

The technical constraint is real, stuff really is hand pixel positioned. It extends to MacOS too. MacOS has a long, sad history of failing to deliver a scalable user interface. As DPIs on their screens have increased, all those UI elements have gotten smaller and there's no way to make them bigger. Lion removed the old half-working arbitrary scaling system entirely and replaced it with a single 2x render mode. Apparently that one works (it's a hidden option), but it's awfully limited.

The marketing simplicity is important too. Too many choices can be overwhelming. It extends to the Mac products. There's 2 sizes of iMac, 2 sizes of laptop, and only 1 size of external monitor. The right size, I think.


From: Charles (Sep 02 2011, at 07:53)

The thing about 16:9 (which seems to be the favoured Android dimension - I haven't seen any Android tablets which aren't) is that in portrait it's too narrow, and in landscape too wide, to use effectively for typing or whatever.

By contrast the iPad and TouchPad at 4:3 seem much more sensible.

So, 4:3 is a ratio of length/side of 1.33.

Compare to A4 (or other A-ratio) sheet of paper: that has sides with a ratio of 1: sqrt2 or 1.414.

US legal sheet: 14: 8.5, or 1.64.

16:9 (most Android screens) is 1.77. That's really *very* thin and long. The 4:3 is closest to A4, and even more square than that. I think there's some subtle effect from it.

As to the selling lots of 7" tablets... well, RIM is trying. Lots are trying. TBH in trying the PlayBook I've never found there was anything its screen did so much better than my smartphone (4" Nexus S) that I needed the PB. Whereas a large tablet can do all the things that lots of real estate can.


From: Andy Lee (Sep 02 2011, at 07:55)

P.S. Having been on a project recently that involves (very) light use of a Nook Color, I agree that 7" is a nice size. I wouldn't rule out Apple doing it someday, no matter what they say.


From: Bud Gibson (Sep 02 2011, at 08:17)

I liked this analysis very much.

Re Apple fine tuning: Android's going to have to do more than a dose of that. I had two Android handsets on Verizon before switching to iphone 4 weeks ago. Figuring out device idiosyncrasies just got to be too much while I was on the go.

I do agree that there's a hole in apple's strategy around device size.


From: Colin Toal (Sep 02 2011, at 08:18)

I think Amazon's tablet with be 7". I have a Galaxy Tab 10.1 and a Kindle, and the Kindle is more comfortable for reading.

A 7" tablet with a PixelQi or Qualcomm Mirasol display please. It would be perfect.


From: Andrew (Sep 02 2011, at 08:44)

Having support in the framework for managing screen sizes, no matter how efficient and foolproof that framework is, still doesn't solve the testing problem. From the Android devs I've spoken to their #1 problem is getting bad reviews for their app because they didn't quite nail it for some specific phone model that had a unique quirk.

Compare that to the Apple ecosystem where even small developers can afford to own a complete set of hardware to test against.


From: Eduardo Pelegri-Llopart (Sep 02 2011, at 08:44)

You already know, but I really like the 7' factor. It's the largest device I can carry along in my pockets and its really easy to hold w/ one hand.

Personally I think we will see much more multi-device situations. Larger is not always better. You should try one of the small BlackBerry Curves - they are a pleasure to hold, and so small you forget they are in your pocket.


From: Phil WIlkins (Sep 02 2011, at 09:36)

It's not about speed of execution, it's about speed of development. Developing for a fixed platform is always easier than for a variable one.


From: Ed Davies (Sep 02 2011, at 10:36)

Real men, women and small furry creatures from Alpha Centauri use meaningful ids on their sections so if they later insert a paragraph "#p-5" doesn't suddenly point at what used to have id="p-4". Does your blogging system allow you to preserve the ids in those circumstances and, if so, how? I thought about it for mine and decided to put up with manually adding the ids.


From: Tim Bray (Sep 02 2011, at 10:46)

Ed Davies: Yes. It's just an emacs function that inserts an h2 and gives it an id= with the next free ID number.


From: ken (Sep 02 2011, at 10:52)

I agree that changing screen size would break huge numbers of existing apps, but the reason you're giving is not correct. I think I can even convince you!

The layout system of the iPhone (springs and struts) is copied from the Mac - it's the same. And it's not quite as manual as you may be thinking. It is, in general Apple style, simple. There isn't much to it, but it's rather shocking how well it works.

Clearly the mac has had resizable windows and varying screen sizes for essentially forever. Thus it is not the technology that is an issue here.

The issue is entirely this: If Joe developer is laying out a pane, and the pane is always fixed size, once it works, is he going to take additional care to make sure it works with a different size pane? Perhaps some might, but the vast majority, no. Now, the pane may work anyway, with fair probability. But only fair. How well do you think your Android interfaces would resize if you never tested resizing them? Many of them would probably work right off, but if 20% don't, that's way past unacceptable to users.

That's it. Existing apps aren't robust against screen size changes because they've never needed to be.


From: Michael Geary (Sep 02 2011, at 11:06)

> It’s plausible, as Nick Farina implies, that iOS’ fixed-dimensions screen model is partly responsible for the astonishingly-fast performance Apple wrings out of the underlying hardware.

I don't see where he implied that. Here's what he said about performance:

"The [Android] rendering system, that is, the method by which UI widgets like menus and buttons and such get painted on the screen, is primarily software-based... you only ever see the final result, so it looks like just a few pixels have changed, but in fact the whole screen must be reconsidered and redrawn... this is the basic method used in GDI, the rendering system introduced with Microsoft Windows 1.0. "

"When you’re using an iPhone, you’re playing a hardware-accelerated 3D game... everything on iOS is drawn using OpenGL. This is why animation on iOS is so hopelessly fast. You may have noticed that -drawRect is not called for each frame of an animation. It’s called once... All the final compositing for each frame is done in hardware by the GPU."


From: Jake Munson (Sep 02 2011, at 11:28)

"The trade-off, if I understand it correctly, is form-factor flexibility for performance and simplicity, and so far that’s been working out pretty well for [Apple]."

Really? Is that why Android has been spanking iOS in sales and market share over the last year? Apple's doesn't seem to understand that you can shove all consumers into the same box. People want different sizes, shapes, carriers, and prices. That is why Android succeeds. Inflexibility will get you a nice little corner of the market, just like what happened with the Mac vs. PC war.


From: Jonas (Sep 02 2011, at 16:21)

Could that "somebody" perhaps be Amazon?


From: Jack (Sep 02 2011, at 22:28)

I agree with the comment that 10" constitutes a tablet, anything less is a PDA.

In fact, I'd go as far as saying that in future anything 10" or above is a PC replacement, whereas less is a PDA/tablet, and I'm sure we will see 12, 13.3", even 14" and 15" tablets.

That's where all this is going. You need a decent sized screen to do real work, anything less than 10" is just for games, media/web consumption, or quick updates.

The tablet format will largely replace the clamshell laptop format, just as it has in phones, made possible because the innards of a laptop have become so small and light now.

Physical keyboards will be optional, though of course important for many tasks, but they can easily be carried with the tablet in a suitable case to make a laptop if that's what you want, no need to actually be attached to the tablet. This way you get the best of portability, while also being able to sit back in an easy chair and type, or read like a book, and of course compute in meetings without having the barrier of a laptop screen between you and other participants.


From: Jeremy Ruston (Sep 03 2011, at 02:10)

The current iPod nano is quite interesting: although the software is not iOS, I think it shows Apple exploring new UI conventions for much smaller screen sizes than the current iPhone. The Nano shows how they could strip away toolbars and status bars, using swiping for navigation, taking advantage of everyone now understanding multitouch.

A sub-3 inch screen might still be quite useful - there's a lot of people watching videos on older iPod Nanos. And perhaps iOS's increasing focus on voice input will deemphasise the need for a big luscious screen.


From: Carl (Sep 05 2011, at 13:47)

Apple are very design-centric. The problem with this is that most hard core graphic designers (the ones I've met are like this) have no idea how to program a computer. They specify their designs in terms of static images rather than any dynamic ideas. Even when they design dynamic graphics they design them in terms of fixed animations rather than interactive animations. They are typically either incapable of imagining dynamic interactive graphics or if they could they have no idea how to express such. They prefer decisions (this rather than that) over choices (this or that). Objects (instances) over classes. A concrete classical universe rather than a virtual quantum mechanical universe.


From: Paul (Sep 06 2011, at 15:37)

@Dave Walker, try two finger scrolling in the text area.


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