gtk:snapshot-rotate (snapshot angle)

snapshot -- a gtk:snapshot object
angle -- a number coerced to a single float for the rotation angle, in degrees (clockwise)

Rotates the coordinate system of the snapshot by angle degrees in 2D space - or in 3D speak, rotates around the Z axis. The rotation happens around the origin point of (0,0) in the current coordinate system of the snapshot.

Use the gtk:snapshot-rotate-3d function to rotate around axes other than the Z axis.