Thank you for your post.
The screen size is the same. The resolution "retina display" just makes the image sharper.
Well that answer is incorrect. The screen is the same dimension in inches (which is rarely a relevant dimension), but it is 4 times the resolution (which is MUCH more relevant when it comes to building screens and interfaces). When I build a background in Photoshop for a FileMaker database, PIXEL dimensions are important... inches are irrelevant.
There are several problems.
1. FileMaker incorrectly reports the screen as 320 x 480 when it is, indeed, 960 x 640.
2. FileMaker Go ends up setting a view size of 200%. iOS takes over to make TEXT high res, but any bit-mapped images present on the layout will look pixelated... as is consistant with graphics in any iPhone app not developed for the retina display. More information needs to come from FileMaker on ways to resolve this... even if it means developing custom layouts for the iPhone 4.