However, using this method will require current-sized Mac displays, which max out at about 130 pixels per inch, to double their X-by-Y resolution numbers.

So a 13-inch MacBook Air would have a 2880×1800 display (currently 1440×900). A 27-inch iMac would have a 5120×2880 display (currently 2560×1440). Using “HiDPI” mode, things on the screen (including the Menu Bar and icons) will have the same apparent size as on current Macs, but everything that supports “HiDPI” mode will be twice as sharp.

Whether such displays can be produced today at the volume and price needed by Apple…? That’s a separate question. But Apple managed to do it for iPad, and still sell it for $499, so it may happen sooner than I imagined possible.

One interesting side-benefit of having pixels that are too small to distinguish, is using the “non-native” resolution settings. For example, someone with weaker eyes may want use a 27-inch iMac set at 1920×1080, instead of the native 2560×1440. This looks reasonably good, even with the current display, because the pixels are already pretty small. But imagine how good it would look, if the pixels became too small to distinguish individually. It would look as good as native 1920×1080 on a true 1920×1080 display.

So, “HiDPI mode” is paving the way (as an interim step) toward true resolution independence in the Mac’s OS.

iOS for iPad had Retina resolution support since last spring. Jobs probably personally used Retina screen test model for like half year.

So the question is whether production will be able to make these screens in value for reasonable price this year, or rather next year.

Also, IGZO-made screens might significantly ease power consumption problem of big Retina displays, but it is not ready yet.

If Apple would want to make Macbook Air with Retina screens now — 2779 × 1800 resolution — they would have to make these devices thicker and heavier because of backlight consumption problem. Only IGZO process would be able to resolve this issue without increase of weight and thickness.