This feature might have been obvious to others, however for newcomers this might not be as self evident.
OCCT has a TurnTable functionality, even though on most samples the default viewer is set to a trackball:
TrackBall's are great when using a 3Dconnexion SpaceMouse and when objects can be viewed from any direction. However, while trackballs are great for looking at small objects, they are a bit disorienting to users when they are looking at objects which have fixed, defined orientations i.e:. car,motorcycle,building,etc
The function V3d_View->StartRotation(X,Y,zRotationThreshold) provides this functionality.
in your code simply replace "V3d_View->Rotate(X,Y)" with "V3d_View->StartRotation(X,Y,Threshold)", give the zThreshold variable a value of 1.
most likely you will have the rotation code inside a switch like this, below I replaced Rotate with StartRotation: