How to accommodate for the iPhone 4 screen resolution?

Question

This is a programming question! Read on before you vote to close!

According to Apple, the iPhone 4 has a new and better screen resolution:

3.5-inch (diagonal) widescreen Multi-Touch display
960-by-640-pixel resolution at 326 ppi

This little detail affects our apps in a heavy way. Most of the demo apps on the net have one thing in common: They position views in the believe that the screen has a fixed size of 320 x 480 pixels. So what most -if not all- developers do is: They designed everything in such a way, that a touchable area is -for example- 50 x 50 pixels big. Just enough to tap it. Things have been positioned relative to the upper left, to reach a specific position on screen - let's say the center, or somewhere at the bottom.

Edit: It seems Apple has integrated an switch that allows to tell if an app is highRes or not. Nice.

When we develop high-resolution apps, they probably won't work on older devices. And if they do, they would suffer a lot from 4-times the size of any image, having to scale them down in memory.

Answer 1

Engadget's reporting of the keynote included the following transcript from Steve Jobs

...It makes it so your apps run automatically on this, but it renders your text and controls in the higher resolution. Your apps look even better, but if you do a little bit of work, then they will look stunning. So we suggest that you do that

So I infer from that, if you use existing APIs your app will get scaled up. If you take advantage of new iOS4 APIs, you can get all groovy with the new pixels.

Answer 2

Yes it is true.

According to WWDC it appears that apple has build it some form of automatic conversion so that the resolution for applications will not be completely off. Think up-convert for dvd to HDTV's.

My guess would be that apple knows what most of the standards developers have been using and will already be using these for an immediate conversion. Of course if you are programming an application to take advantage of the new resolution it will look much nicer than whatever the result of apples auto-conversion is.

Answer 3

This is purely speculation, but if the resolution really is 960 x 640 - that's exactly twice as high a resolution as the current version. It would be trivially simple for the iPhone to check the apps build target and detect a legacy version of the app and simply scale it by 2. You'd never notice the difference.

Answer 4

It sounds like the display will be ok but I'm concerned about the logic in my game. Will touchesBegan positions return points in the new resolution? The screen bounds will be different, these types of things could potentially be problems for me.

Answer 5

Scaling to a double resolution for display purpose is straight forward, but will this scalling apply to all api's that input/output a screen coordinate? If not things are going to break aren't they?

Fair enough if it's been handled extensively throughout the framework.. I would imagine there are a lot of potential api's this effects.

Answer 6

Page 75 of the latest (2010-06-04) iPhone App Programming Guide.pdf:

https://developer.apple.com/iphone/prerelease/library/documentation/iPhone/Conceptual/iPhoneOSProgrammingGuide/SupportingResolutionIndependence/SupportingResolutionIndependence.html

You will get access to this if you are a registered Apple Developer. Any discussion of iOS4 and it's features is prohibited except on Apple's own forums.

Answer 7

For people who are coming to this thread looking for a solution to a mobile web interface, check out this post on the Webkit blog: http://webkit.org/blog/55/high-dpi-web-sites/

It seems that Webkit has solved this problem four years ago.

Answer 8

All of your labels and system buttons will be at 326dpi but your images will still be pixel doubled until you add the hi-res resources. I am currently updating my apps. If you build and run on the iPhone 4 sim then it is presented at 50%, go to Window > Scale > 100% to see the real difference! Labels are smooth, my images look shocking!