That's not what I'm saying. I'm not pitching scaling up from 1024 x 768. I'm talking about scaling down from full-sized iPad retina: 2048 x 1536. Unless I'm missing something, scaling down to- say- 82% of the resolution should work as good as scaling down a 1080p movie to fit- say- a 1024X768 screen now (only my suggested scale would not be nearly so much and would maintain the exact same full-size retina aspect ratio).
You're point is about points. Could the pixel resolution scale to about 82% but the point model work in fractions? In other words, can it definitely NOT work or could the pixel resolution slide down to- say- 1679 X 1259 for a iPad Mini 2 while the point system just adapts to approx. 82% of full-sized iPad retina points. If the coordinate system is just the model to track where buttons begin & end, it seems like this could work. Graphics would be just as sharp- just smaller- and coordinates would just scale accordingly.
Conceptually, this would be like taking a full-sized iPad with retina screen and trimming it down to 7.9" for an iPad Mini 2. This would lop off a bunch of pixels in both dimensions and result in a screen that is about 82% of the original. That yields the same ppi metric (the remaining pixels would still be packed in exactly as before) only a smaller resolution (to about 1679 x 1259 rounded up or down a few points to get it exactly right for byte sizes, etc.
Or maybe the coordinate system must be integer based (no fractions)? I'm not a iOS developer, so I don't know. I just have a harder time imagining the iPad Mini 2+ has only 2 options for a new display- stay at 1024 x 768 or double to 2048 X 1536. Nobody expects the former. Everybody expects "retina" for version 2, but if 2048 is the ONLY option for retina, then the iPad Mini 2 will have the sharper screen vs. the iPad 5 (pixels will be more densely packed). I just don't see the smaller, cheaper iPad ending up with the (arguably) sharper screen.
So, if we assume THAT, then maybe Apple officially picks another size somewhere in the middle. Does that mean the coordinate system of points requires a big overhaul to support a new Apple-selected retina screen resolution somewhere in the middle? If Apple picked iPad Mini 2 resolution around 1679 x 1259, what happens?
You're still not getting the distinction about iOS screens being mapped to points not pixels.
It works if you scale a movie because most screens work in a 1:1 ratio - a 1920x1080 screen really has 1920x1080 'points'. If you scale that down to a smaller screen, you are able to retain quality because you retain the 1:1 ratio - the file is just down-converted to a lower resolution and then displayed with that many pixels. This works very well for pictures and movies.
With iOS's point system, this doesn't work. Each point is defined by a mapping to pixels. Again, a non-retina screen has a 1:1 mapping - on an iPad, that's 1024x768 pixels and 1024x768 points. On a retina screen it's a 2:1 mapping - again, on an iPad, that's 2048x1536 pixels and still 1024x768 points.
This is why the screen is so sharp. 2 pixels = 1 point.
I'll say it again because this is the crux of the issue - a retina iPad does not have 2048x1536 points to work with, it is merely displaying content with 1024x768 points with extra clarity because it uses more pixels to draw the same points.
You can't scale that to 1679x1259 because you only have 1024x768 points to work with. That's what all iPad apps are designed with; they are not designed to scale down because they don't assume a 1:1 mapping to screen pixels. In order to display your proposed resolution, you'd have to be able to map the 1024 vertical points to 1.6396... pixels, and you can't activate a fraction of a pixel.
Now there IS a way to do what you are talking about, in fact this is exactly what Apple is doing in the existing retina Macbooks. Natively the 15" model has a panel 2880x1800 but everything is scaled as if it were 1440x900 (same 2:1 mapping as in iOS). They do, however, offer options to render the desktop at 1680x1050 or 1920x1200 giving you more useful workspace. However, in order to do this, they must perform some trickery.
From
this article at Anandtech:
If you select the 1680 x 1050 or 1920 x 1200 scaling modes, Apple actually renders the desktop at 2x the selected resolution (3360 x 2100 or 3840 x 2400, respectively), scales up the text and UI elements accordingly so they arent super tiny (backing scale factor = 2.0), and downscales the final image to fit on the 2880 x 1800 panel. The end result is you get a 3360 x 2100 desktop, with text and UI elements the size they would be on a 1680 x 1050 desktop, all without sacrificing much sharpness/crispness thanks to the massive supersampling. The resulting image isnt as perfect as it would be at the default setting because you have to perform a floating point filter down to 2880 x 1800, but its still incredibly good.
As you might expect, this takes a massive amount of power as the system is having to render 4x as many pixels as it was ever intended to. Apple put a ton of work into getting this working in the Macbook line, but even still if you choose those resolutions that are not direct multiples, performance and image quality starts to suffer. In order to do this on your hypothetical 1679x1259 pixel display, it would first have to render the display at 3358x2518 and then downscale the image to fit on your 1679x1259 panel.
Eventually the graphics power needed to perform this kind of work will be available on the mobile platforms, but I wouldn't count on it for next year. Maybe a couple of years from now.
