One of the most iconic ships in all of Star Wars, the B-Wing resembles more of a t than a b. Other than that, its cockpit is located at one end of the ship and can be seen to being able to change orientations.
Q: Is there any source describing how the cockpit changes its orientation and how it decides what the correct orientation is?
Per the Star Wars Databank article on the B-Wing, the pilot decides whether to lock the gyro to a local horizon or, presumably, to let the cockpit align itself with the orientation of the ship itself.
The B-wing's command pod has a unique gyroscopic control system. The pilot can orient it so that it always stays level with a horizon line. No matter which way the B-wing may maneuver laterally, its pilot remains upright.
This is discussed at some length in the (Legends) video game Star Wars: Rogue Squadron II: Rogue Leader
Because the cockpit is surrounded by a unique gyro-stabilization system, the pilot always remains stationary, even as the rest of the ship rotates during flight.
And in this image from Star Wars: Card Trader. Note that the image was originally taken from a set of Legends blueprints found in the Essential Guide to Vehicles factbook.
And you can see how it would work in practice.
