The best example of RI is printing. If you print the same page at 300 dpi, 600 dpi and 1200 dpi you get the same content but different quality. The support for this was first implemented by Adobe. Adobe's PostScript is what made them a big company and where they started from. Photoshop and InDesign were much later.
Back then, when the laser printers were 300 dpi the main issue which needed to be addressed were fonts. At the time, non-PostScript printers were using bitmap fonts. Rendering fonts on 300 dpi printer had the following problems to be addressed:
- The stems of a letter which were supposed to be equal could be different. For example, when printing the letter H you could get 3 pixels for the left stem and 4 pixels for the right stem. This was visible and unpleasant.
- the letters could go above or below the baseline by 1 pixel. This was visible and unpleasant.
- at certain sizes, some letters could break. For example, the letter o could end up not being closed.
- The fonts needed to be rendered on-screen at much lower resolution and still look good.
These problems were resolved.
The problems with RI now are related to the UI elements quality and alignment. The problem of pixel number and processor load is non-existent. The pathetic iPhone CPU (compared to the notebook and desktop CPUs) can handle very high resolution display acceptably. Why worry about the much more powerful (in an order of magnitude) dual/quad core CPUs and GPUs?
The amount of work for developers is also overestimated on this board. To begin with, Mac OS drawing engine is resolution independent from 10.0. Remember, NEXT was using Display PostScript, and Quartz uses PDF.
To get an idea what are the problems to be fixed, install Developer Tools (on your Mac OS CD). Then find an app called Quartz Debug and browse the menus to locate the right one (I am on XP right now). It has the word scaling in it. Change the scaling and (re-)start some apps. You will notice that 99% or more of the problems are with Finder, menu bar icons and standard UI elements. It's all in Apple's basket. Most apps need to do close to nothing to work absolutely fine.
Take a look at this document:Resolution Independence Guidelines
. Note the revision history. It was first written in 2006 for god's sake! So Apple does not need to do ANYTHING
to "bring developers on board". Apple is telling them to get ready for RI for three years now!
If the Marble UI rumor is correct, the folks at Apple should be complete and utter idiots to make the new UI not RI ready. All evidence is that they are not idiots. Carbon is dead as well. Finder is supposed to be re-written. What's left? There might be show-stopper issues of course, but I hope not. If the Marble UI is not coming with SL but planed for 10.7, it does not make sense to fix the old UI if a new one is in the works.