The controller is split into two sections.  The callbacks subdirectory
contains the functions that are used as callbacks from the GLUT event
loop.  The actions subdirectory contains functions that operate on the
data and state.  To the extent possible callbacks should be empty
shells that transform information from hardware and the event loop to
the calling parameters of actions.  This design has the advantage of
facilitating the scripting of user actions in the future.  A script
should be able to call action functions and generate equivalent
behaviors as if the user had initiated the sequences of actions using
the user interface.  Another advantage is that multiple user interface
callbacks can share the same actions.  A common example of this is the
execution of the same function through either a menu selection
callback or a toolbar callback.  As per the "GNU Coding Standards"
section "5.4 Naming Variables, Functions, and Files
[http://www.gnu.org/prep/standards/html_node/Names.html#Names]"
underscores should be used to separate words in a name.

 LocalWords:  callbacks callback