So 9to5 Mac’s going with the argument Apple’s next iPhone will have a 1704-by-960 display. The report might well turn out to be right, but there are some curious arguments within the text.

Apple claims that a display density over 300 PPI is considered “Retina” quality

Apple’s played fast and loose with what it deems a Retina display, and as Richard Gaywood pointed out long ago, high-res displays are reliant on context. Larger screens tend to be used further away, meaning they need a lower ppi to be considered Retina. The iPad Air, for example, clocks in at 264 ppi, but Apple’s hardly shied away from saying that device has a Retina display, despite the screen’s pixel density being lower than an iPhone’s. On that basis, there’s no reason Apple couldn’t keep much the same resolution as on the current iPhone, but just make the screen bigger.

9to5Mac, however, argues that we’re going to see 1704-by-960, and it rationalises this on the basis that it’s akin to a 3x mode; the logic is iOS has a base resolution (568-by-320), and existing Retina devices are 2x (1136-by-640). The suggestion is that in merely adding another ‘x’, things will be relatively easy for developers:

According to sources familiar with the new iPhone displays in testing, if an unoptimized iPhone 5 app is run on the iPhone 6, the app will fill the entire screen but the non-3X images within the app will be blurrier. Troughton-Smith’s applications scale well because they were built with vector graphics. This transition from 2X to 3X will be reminiscent to the transition from 1X to 2X when the first iPhones with Retina displays launched in 2010.

This seems hugely optimistic. The shift from 1x to 2x was relatively simple, in that apps could simply be doubled and still look reasonably OK. Today, however, all apps must be Retina, or they’re likely to be rejected from the App Store. Support for 1x is therefore now pretty ropey.

When it comes to 3x, then, we’d not see sharp but jagged upscaling from 1x, but a blurred mess as apps designed for existing Retina screens are upscaled to 150 per cent. Perhaps this is what Apple has in mind, but if so, countless games and apps are going to look like absolute crap on such a display. And even with iOS 7’s design dialling down reliance on texture-heavy raster-graphics, adding yet another resolution and, potentially, another scaling factor is something likely to have developers headdesking until their foreheads bleed.