The inclusion of an accelerometer allowed the original iPhone to detect changes in its physical orientation; reflowing its on-screen content to suit the user's preference for either portrait or landscape viewing. Offering this, however, meant that an application had to be designed and coded for two screen aspect ratios—one for the portrait and another for landscape.
As the iOS family has grown, so too has the number of screen resolutions that must be supported. With the launch of the iPad and the introduction of Retina display devices, there are now three separate resolutions. If you also take into consideration the two aspect ratios, then screen layout management for your application can become daunting.
This chapter provides recipes that will help you render content properly on any iOS device, regardless of its screen resolution and physical orientation.