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Comment by jeswin | Hacker News Reader

It was useful for paper because it helped save time in cutting, folding, printing etc. None of that matters for a phone.

This is such a non issue given that iOS developers already have so many resolutions to test.

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> None of that matters for a phone.

Of course it does. They show the most basic example right on the page, which is that you can side-by-side full screen apps.

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.

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.

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 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.

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 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)

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.

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.

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.

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

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.

Apps already work on Apple devices with many different aspect ratios.

This way you don't need to design your app to work with different aspect ratios, because it's always the same.

But you still do need to support different aspect ratios if you want your app to work on any other iPhone models, because many of them differ.

Ok? I didn't say this iphone would solve all aspect ratio issues ever. It can only solve the problem for the space it controls, e.g. itself.

that still means it's effectively useless to app developers. who here is creating apps solely for the duo?

Even if it were true you would also have to design the app for when the device is rotated.

Easier to support one more aspect-ratio then two.

Unless these things start selling like hot-cakes (unlikely at the price) a lot of developers just might not bother.

Hm, my folding phone doesnt have this aspect ratio and I can still do that.

I think they intended to continue "... without changing their aspect ratios".

I.e. an aspect ratio of Sqrt(2)is the only one where the inner screen (full) and inner screen (half) match, and they seem to have tried to make the outer screen share a nearly identical aspect ratio too. I guess it's a nice consideration for more consistency in layouts for apps targeting the device. Not sure I'm particularly excited about that myself though.

it's a neat tidbit, but not important in the slightest imo. Probably helps with smoothly transitioning between modes, but that's not been a particular pain from my foldable use.

Android devs have always had to handle different screen sizes. Not the case for iPhone devs e.g. I have a game "Ridiculous Fishing" (from 2013) which is a mess layout-wise on my iPhone because it seemingly hardcoded some pixel values and used percentages for the others. They have a fixed version for Apple Arcade.

The first new resolution for an iPhone was 2012 which also saw the introduction of Auto Layout. The second new resolution was in 2014 which added size classes. It's entirely possible that the 2013 game was built before they actually started caring about this. This is a non-issue for almost all apps you're realistically going to encounter.

>I think they intended to continue "... without changing their aspect ratios"

but the context was "see, you can have two different apps running side by side, each with the same aspect ratio as either of the apps when run in the space of the folded screen. not only the same aspect ratio, but the same dimensions"

the whole A3/4/5 scheme is completely overblown as a feature for consumers. You format a document for A4, ok, but you wouldn't print that document A5 because the fonts would be completely shrunken. nobody does that. We use word processors to format documents for the space we have, and we don't ever print wedding invites on A3 or A4

This would matter for bigger versions of the same thing. For side-by-side, the aspect ratio is unimportant since you naturally unfold to have two of them.

Not sure if I'm misunderstanding you, but of course the aspect ratio is important. If you unfold a square, you don't get two squares.

I think the person you are responding to is not thinking visually. They basically seem (to me) to think reformat-flowed fixes this, and that having the view of a web page alter because you open a book, is "not a bad thing" when you (and I) are of the view, if you maintain the aspect ratio and simply decimate how many pixels are available to show it, the actual "change" in the layout is kept to a minimum WHICH IS THE INHERENT GOOD HERE -the whole point of the A, B and C series is that the scaling function preserves the ratio of sizes of the contents, under the quality change of bigger or smaller fidelity of presentation.

Unless there is some upsight I am missing, I think the OP just "doesn't get it"

The upsight is that they are responding to a point about side by side apps, not a single full screen app on the unfolded screen

I don't think this is a killer logic either. If you consider that the apps were both running, both full screen on the folded state and alternate which is in view, and now can come into view side by side when you open, surely the "good" is that nothing positional in the layout or styling changes, when you move from swipe-and-select to side-by-side.

>If you unfold a square, you don't get two squares.

yes, you do. Two squares will fold together into the space of one square, and the same with 2 A4 sheets of paper, or two 8½x11 sheets of paper, two of them will fold together to make one of them.

I'm not exactly sure what you're trying to say, or what would refute what I said.

You said: "If you unfold a square, you don't get two squares."

In the context of this discussion, it is reasonable to assume that any "square" available to be unfolded is something approximately like the folding phone, consisting of two layers joined by a hinge. When you unfold that, you go from having a square to having a rectangle equivalent to two adjacent squares, and usable as two adjacent squares.

I see. I agree (obviously, it's a fact), but in the context of this discussion about aspect ratios and why the golden ratio would be relevant to this situation, it is reasonable to assume that the point here is that a full-screen, unfolded image would scale exactly to a half-screen/folded image with no change in aspect ratio.

>it is reasonable to assume that the point here is that a full-screen

wrong. you answered under the context of yunwal's comment https://news.ycombinator.com/item?id=49630931#49634166

  > None of that matters for a phone.
  Of course it does. They show the most basic example right 
  on the page, which is that you can side-by-side full screen 
  apps.

which is talking about the case of two separate apps running side-by-side (unfolded), as was shown in one of the pictures of the device.

Right, which is under the context of hbarka’s comment

> The iPhone Duo is designed with this in mind. The aspect ratio any way you view it, folded or open, is preserved. Apple design knows a thing or two.

which is talking about the aspect ratio being preserved in the open and folded/half modes.

that's not how threading works

there were plenty of other threads under that comment in that direction

> it is reasonable to assume that the point here is that a full-screen, unfolded image would scale exactly to a half-screen/folded image with no change in aspect ratio.

Sure, but aside from being interesting from a mathematical standpoint, there are no practical implications from that fact. When the user unfolds the phone and rotates it by 90 degrees, the fact that they're left with about the same aspect ratio (modulo whatever changes with status bars, etc.) means very little for UI design in light of the much more important fact that the screen doubled in size and thus the application's layout should be using the extra screen space to show more information, and should not assume that a majority of the screen is easily reachable by a thumb.

But apps can just rejigger into widths that fit. It would be more of an issue back when mobile sites were first becoming responsive and we pragmatically chose 2 or 3 media query widths to serve different layouts and then applied the same thinking to mobile apps. Of course the initial mobile apps, particularly on iPhone, stuck to just one and later just a few sizes themselves. As there was a wider range we did things more responsively on a continuum.

I still think the broader point of there being design reasons to hit these ratios stands and is great. I just think the idea that it needed to be precisely twice the width so apps can fit full-sized doesn't hold too much because there isn't really a "full size" notion. Or if there is, the full-size is probably the double width one. If it wasn't exactly twice the width, most apps are already built to fit into varying iPhone/mobile screen widths.

App rejiggering is not an exact science, and is often poorly done.

Even if apps transition well between aspect ratio / screen size breakpoints, there is a cognitive load to maintain 2+ UI configurations.

Preserving aspect ratios eliminates these issues. It'll make every app better.

^^This.

Despite all the responsive design tools and declarative layouts to ensure a great layout even on an oddball resolution... the fact is that in practice it's nontrivial, and remember that the companies that make most of the apps you use have finite design and QA budgets. They need to actually use the resolution in question in order to really do a good job of designing for it, and giving them double the work, for a $2000 and up phone which probably won't be super highly adopted, is a recipe for getting apps that end up with layouts that aren't optimized properly on one (or both) of the screen sizes.

My point is largely that the nontrivial work you've described is the norm today. What's being asked for tomorrow is not new. Most apps are already set. Not just because of work Apple does to make it easier for apps to "port" out of the box, but because the multiple sizes that apps are already prepared to handle across iPhones, iPads, and resizeable iPad apps (and to the extent that devs are having React Native handle this, then across Android too).

So it's a lot of work, yes, but it's work that's already been done and that engineering teams already assume in their processes. The future is the same because this has been the status quo for a few years. Whether the Duo has a 2:1 ratio or something slightly different, the apps are at about the same readiness for it.

I'm not calling you a liar or anything, I get that yeah, no apps really survive today that are laid out statically for each resolution.

I'm just saying that they don't release a new version of Uber, Instagram, etc. without checking to see what that flexible and responsive layout looks like on the most popular devices and, where important UI ends up suboptimal on one of them, it'll be tweaked before release. And I'm saying that nobody really wants more of these 'significant formfactors' to check.

Uber Eats is a good example of a website that handles different screen sizes poorly.

This is already something every app needs to deal with on iPad, where users can arbitrarily resize apps and windows. And apps that support landscape layout on phones have always needed to support their UI being rendered in different aspect ratios.

At WWDC this year, Apple introduced a tool[0] to let developers arbitrarily resize their simulated iOS device screens.

Flexibility and adaptivity are more front-and-center for iOS devs than ever.

[0]https://developer.apple.com/documentation/xcode/configuring-...

I agree it will feel super nice to go from the front screen to the dual screen and have nothing "move". And similarly it will feel "mildly infuriating" if it doesn't do that.

I also think that I (personally) don't need a front screen and would love to have whatever cost savings or improvements would come if there weren't one. This last sentence is of course a me thing, but I mention it because I think that if people start on the front screen and then open the Duo, they may just want the full screen app or something else entirely. I'm not sure the use case of being in your banking app device folded, deciding midway through flow to open it, and wanting to be in the same UI is really what I want. The part I question is what's going on that step 2 came about—I think it's either you want to go into more depth on it or you're just opening the device the way you would had you not been in your banking app.

The case where I open it to find the app using half the screen and then I have to press something or drag something to make it full screen is not that great (and isn't great today with current iPad window resizing). The best case I can think of for wanting the app in the same size format when I open it is for is something like multitasking, I guess we'll see how that looks or feels and how you get the second app open (or whether it's very common use case anyway).

In general, I've long felt the folding tech is for tablet use cases not for phone use cases. I think Apple's foray (finally) into it more or less validates that. Even though there will be a meaningful number of people buying it to replace their phone, I think this is largely because their phone use is already tablet use case-y (for entertainment especially). I assume many people will also buy it as a(n expensive) tablet replacement in addition to their phone, which is perhaps related to the timing of iPhone Handoff (same SIM on two phones) too.

Proportions absolutely matter for displays, both for aesthetic comfort and for efficient scaling. Most of the world uses ISO216 and its pleasing 1:sqrt(2) proportions. Leveraging aspect ratios with wide acceptance is a win both psychologically and for graphic designers.

The algebra proving why "halving long side H and flipping maintains aspect ratio" implies a ratio of 1:sqrt(2):

    H/W = W/(H/2)       (halving long side H and flipping maintains aspect ratio)
        = 2W/H          (multiply numerator and denominator by 2)
    H²  = 2W²           (multiply both sides by HW)
    H   = √2·W ≈ 1.41 W (take the positive square root; H, W > 0)

Our world is full of artifacts from a previous ages and using some of those as standards is useful/convenient.

We still use QWERTY keyboards even though our highly futuristic typewriters don't jam anymore. We type commands on tty teleTypeWriter, we save files with buttons using a floppy disk icon, etc etc.

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