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.

▲ guyzero 3 hours ago | parent [-]

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.

▲ Wowfunhappy 2 hours ago | parent [-]

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

▲ wtallis 23 minutes ago | parent | next [-]

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).

▲ guyzero 44 minutes ago | parent | prev | next [-]

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.

▲ wavemode 33 minutes ago | parent | prev | next [-]

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.

▲ mrmanner an hour ago | parent | prev [-]

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)

▲ jaggederest an hour ago | parent [-]

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.