This is a re-implementation of the loupes (magnifying glass) that Apple uses for text selection. DTLoupeView represents the “magnifying glass” shown when positioning a caret or ranged selection. It has three different styles: the regular round loupe, a ranged selection loupe with an arrow at the bottom and a rectangual loupe without arrow.
The loupe is using it's own private UIWindow so that it can always stay in front of other views.
Documentation for DTLoupe can be browsed online or installed in your Xcode Organizer via the Atom Feed URL.