SoPickAction(3) on Linux
The text 0f61489ca1a3, as Debian 8 (Jessie) shipped it.
The SoPickAction class is the base class for picking actions. The basis for all interaction features that Coin provides for the application programmer is the pick actions. Draggers, manipulators, SoSelection nodes, etc all make use of the functionality provided by the pick actions for selecting and manipulating scene geometry in various ways.