oracular (3) Manipulator.3U.gz

NAME

       Manipulator - base class for defining direct-manipulation semantics

SYNOPSIS

       #include <Unidraw/manip.h>

DESCRIPTION

       Tools  use  manipulator  objects  to encapsulate the mechanics of direct manipulation.  Manipulators turn
       user input events into an animation sequence that characterize the manipulation.   Manipulators  abstract
       the manipulation into three phases: the grasping phase, which occurs at the start of the manipulation and
       lets the manipulator initialize state it will need in later phases; the manipulating phase, during  which
       the  manipulator accepts input events and generates graphical output that characterizes successive frames
       of the animation; and finally the effect phase, which occurs at the end of the manipulation and lets  the
       manipulator  finalize  its  state.   Manipulator is an abstract base class.  Subclasses support different
       manipulation semantics.

MANIPULATOR PUBLIC OPERATIONS

       virtual void Grasp(Event&)
              Grasp is called once at  the  beginning  of  direct  manipulation  to  allow  the  manipulator  to
              initialize its internal state based on the initiating event.

       virtual boolean Manipulating(Event&)
              Manipulating  is  called repeatedly during the manipulation whenever a new event arrives, until it
              returns false.  Each call to Manipulating should  produce  a  new  frame  of  the  animation  that
              characterizes the manipulation.

       virtual void Effect(Event&)
              Effect  is  called once at the end of direct manipulation to allow the manipulator to finalize its
              internal state based on the last event supplied to the Manipulating operation.

       virtual void SetViewer(Viewer*)
       virtual Viewer* GetViewer()
       virtual void SetTool(Tool*)
       virtual Tool* GetTool()
              Get and set the viewer, in which the manipulator generates graphical output,  and  the  tool  that
              created  the  manipulator.   These  operations do nothing by default; subclasses that require this
              information must redefine these operations to assign and retrieve the state they require.

MANIPULATOR PROTECTED OPERATIONS

       Manipulator()
              The constructor is protected to disallow instantiation of abstract base class objects.

SEE ALSO

       Event(3I), Tool(3U), Viewer(3U)