Resolution independence (sort of) today

[Graham Samuel]

Thanks Colin Holgate for your excellent explanation of what resolution independence is and isn't, or rather what it could be when implemented. I have an issue in this area right now, and I suppose I will find the answer in the docs somewhere, but meanwhile could some one give me a quick answer?

I have an app that works in Landscape only on an iPad 2. I want to adapt it for the most recent iPads, which of course have twice the number of pixels in both directions (Retina). I'm quite happy to re-work my app to fill this larger space properly - there are quite a few images, which I need to revise to make them properly sharp etc. I am confident that I can make the app look good on the Retina screen.

The issue is, what happens when a retina-style app like this runs on an iPad with the lower resolution? Can the reduction be achieved automatically, or do I have to create in effect two versions of the app to get it to work? Obviously what I want is for all the objects on the screen to be automagically reduced in size, while retaining the original location information - so far example an object at the centre of the retina screen would be at (1024,768): if I show this on a pre-retina screen, do I have to change the loc to (512,384) and by implication change all the locs of all the visible objects, or will iOS do it for me?

Sorry if this obvious to everyone else.

TIA

Graham