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Comment by guyzero | Hacker News Reader

this isn't great design, it's tautology. of course the phone open is twice the size of it closed. it would be hard to make it otherwise.

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You have to understand 1:√2. It’s not merely folding in half. The test is the folded half has to be the same ratio as the parent. It’s same ratio all the way down.

“The mathematical brilliance of A*”

https://youtu.be/oQfzSt5bLVs

You are not answering the parent comment. If the original aspect ratio was a square, making the "full screen" aspect ratio 1:1, then folded out it would have aspect ratio 2:1, fitting two squares side by side.

The sqrt(2) aspect ratio allows a portrait full app to be scaled up to the exactly to the folded out screen. But does anyone want that? You probably want to fit more content on the bigger screen, so some layout necessarily changes.

It's still folding in half, so you can have have one app taking up the whole screen, or two half-screen apps, all with the same aspect ratio.

But its two states. What do you mean “all the way down?”

You can keep folding it and it keeps the same aspect ratio. Scaling becomesa simple matter of multiplying everything by 2^+/-n.

Everyone knows its impossible to fold a smartphone in half more than 7 times.

I failed at 2 times. My folding couch couldn't supply the required pressure beyond that point.

It isn't just twice the size.

Both sides have the same aspect ratio as the whole screen.

> this isn't great design, it's tautology. of course the phone open is twice the size of it closed.

Well, it sounds obvious now, but before Archimedes, ancient engineers split their screens 60-40, so the full screen wasn't twice the size of either side.

Yes, I do understand the issue with the aspect ratio, which is indeed good design, but parent comment's example is that "you can run two apps side by side" is the tautology. Well, at least since the invention of double-entry bookkeeping and getting rid of Archimedian phone design.

No, you can't, unless the apps are designed for different aspect ratios.

If the outer screen has dimensions X by Y, then you unfold it to have the inner screen with dimensions 2X by Y, which cleanly permits side by side apps at the original dimensions of X by Y. This is true for any ratio between X and Y.

If the user isn't going to be multitasking, then the app needs to additionally support the widescreen dimensions of 2X by Y, and the portrait orientation of Y by 2X. Both of these are so drastically larger overall that aspect ratio is a barely-relevant part of the UI layout problem, because nobody wants every button and text label to be double the size (which would mostly defeat the benefits of having the larger screen for anything other than multitasking).

The inside screen, when divided in two vertically, along the fold line, is exactly the same dimensions as the outer screen. Pretty much by definition. Any folding phone, of any aspect ratio, can run two apps on the interior display side by side.

The issue of the internal screen being the same aspect ratio as the external when rotated is completely separate.

But, the iPhone Duo has a different aspect ratio from a regular iPhone. So your app needs to be designed for multiple aspect ratios anyway.

which they have to be anyway, to support normal iphones and maybe ipads and in many cases a cackle of Android phones too. (but I still think this is brilliant design)

in this thread many people have clearly never developed for iOS

Here's just the screen sizes, not even taking into account actual resolution:

    iPhone (2007)     3.5" 74.0 × 49.3    36 cm²
    iPhone 5          4.0" 88.6 × 49.8    44 cm²
    iPhone 12 mini    5.4" 124.5 × 57.5   72 cm²
    iPhone Duo, cover 5.4" 113.4 × 77.2   88 cm²
    iPhone 6 Plus     5.5" 121.8 × 68.5   83 cm²
    iPhone X          5.8" 133.7 × 61.8   83 cm²
    iPhone Air        6.5" 150.0 × 69.1  104 cm²
    iPhone 18 Pro Max 6.9" 159.2 × 73.3  117 cm²
    iPhone Duo, inner 7.6" 157.6 × 111.5 176 cm²

Now, you can leave out a few of those as hopelessly obsolete like the OG iphone, 5, 12 mini, arguably the x, but it's still a pretty wide selection.

Good list. And if you support both portrait and landscape, you need to support twice that, and you need to be able to switch on the fly.

But for the apps that don't currently support both orientations, it's possible they don't have support for switching aspect ratio on the fly. This design might help with those apps not completely breaking when folding/unfolding.

Yeah to be fair I'm all for the 1/sqrt(2) aspect ratio, I just think it's funny that it's treated as some kind of holy design constraint when they're all over the map on phone sizing :)

And the extra irony is I'm currently shipping an app that doesn't deal well with different size phones (just pads the edges), heh, so do as I say, not as I do.

12 mini and 13 mini remain supported in iOS 27.

The missing piece that makes it not a tautology is that two apps side by side have the same aspect ratio as one app full screen (but 90 degrees rotated)

first - it's not hard to make. Outside screen size doesn't have to be half of the open screen.

second - main idea is about proportions, if you want to design apps that seamlessly transfer from one screen to another they have to have the same proportions of the sides. This is not a given and depends on the height and width.

If you take iPhone 18 Pro resolution : 2,622 x 1,206 doubling it would make the screen with 2,622 x 2,412 - almost a square screen.

They chose to have the folded phone to have 1.4:1 aspect ratio which is consistent when folded and when unfolded.

What app is going to design to flow nicely with a iPhone Duo but not a iPhone 18? Unless Apple has a 1.4:1 ratio across their entire product line, app designers have to deal with variation.

Also, when you rotate the device, the ratio changes. This is especially common when unfolding a foldable.

Folded and unfolded will both be designed for 2 aspect ratios. 1 for Portrait and 1 for Landscape. Opening the fold and rotating 90 deg will give you the larger version while keeping the aspect ratio

"larger version while keeping the aspect ratio" is of minimal benefit. You still need to present a different layout, because eg. any toolbar is going to be a different fraction of the available area depending on whether the app is on the small outer screen or the large inner screen in portrait orientation. Nobody wants a naive 2x scaling of the phone app on their iPad.

The tools can look however the dev wants them to. The utility is for content. It is an aesthetic choice

You don't seem to be engaging with the point, which is that the space available for content after subtracting out the space taken up by other UI elements is not going to have the same aspect ratio folded and unfolded. A real UI doesn't actually get this supposed benefit. Only something like a full screen video player might (depends on what kind of keep-out zone you need for the front camera), and maintaining the same aspect ratio folded vs unfolded for video content isn't particularly helpful when the aspect ratio in question isn't popular so you'll have letterboxing regardless.

You're right, it will only look the same for content where the other UI elements disappear

People keep saying it’s so an app can resize to the full interior screen but none of the marketing photos actually have this. So its hard to say “what a genius masterstroke by Apple.”

Most have the closed screen plus another view. Or the lock screen which is a full photo open and a small section closed.

Im not saying its not possible but it doesn’t seem like that is their intention.

A lot of people will look at this and say. Eh I already have an Ipad and a Imac why do I need a phone with such a large screen.

Their selling point is: Not having to switch from one app to another when Multitasking.

The difference is that it has the same aspect ratio folded and unfolded. If you look at other folding phones the inside screen is twice the area, but the shape of the phone is different. 1 : sqrt(2) is the only ratio where you can fold one side in half and the ratio stays 1:sqrt(2). Any other ratio of sides and the inside and outside have different ratios. Therefore, things have to move around, or scale.

Yes, but 1:√2 keeps the ratio even when you rotate the screen vertically. A folded 1:1 screen becomes 2:1 when "unfolded" and the area doubles, so you can go from showing one 1:1 window to two 1:1 windows side by side. But when rotated to a vertical orientation, you can't just scale that 1:1 window to double its size. With 1:√2 you can.

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