Class Controller

object --+
         |
        Controller

Known Subclasses:

ConstantController, EncapsulatedController, EvalStringController, ExecStringController, FunctionController, LPTTriggerInController, LPTTriggerOutController, PyroListenController, SocketListenController

Control parameters.

This abstract base class defines the interface to any controller.

Methods:

returns_type() -- Get the type of the value returned by the eval functions
during_go_eval() -- Evaluate controller during the main 'go' loop.
between_go_eval() -- Evaluate controller between runs of the main 'go' loop.

The during_go_eval() and between_go_eval() methods are called to
update a particular parameter such as the position of a stimulus
on the screen.  These methods must return a value specified by the
returns_type() method.  These methods are called at particular
intervals as specified by eval_frequency and with temporal
parameters specified by temporal_variables (see below for more
details).  Also, see the documentation for the Presentation class.

Attributes:

return_type -- type of the value returned by the eval functions
eval_frequency -- when eval functions called (see above)
temporal_variables -- what time variables used (see above)

A Controller instance's attribute "eval_frequency" controls when a
controller is evaluated. This variable is a bitwise "or" of the
following flags:

Controller.EVERY_FRAME    -- every frame
Controller.TRANSITIONS    -- on enter and exit from go loop
Controller.ONCE           -- as above and at the next chance possible
Controller.NOT_DURING_GO  -- as above, but never during go loop
Controller.NOT_BETWEEN_GO -- as above, but never between go loops

If none of these flags is set, the value is:

Controller.NEVER          -- this controller is never called

The Controller.ONCE flag is automatically unset after evaluation,
hence its name. As an example, if eval_frequency is set to
Controller.ONCE | Controller.TRANSITIONS (the bitwise "or"), it
will be evaluated before drawing the next frame and then only
before and after the go loop.

A Controller instance's attribute "temporal_variables" controls
what time variables are set for use. This variable is a bitwise
"or" of the following flags:

Controller.TIME_SEC_ABSOLUTE -- seconds, continuously increasing
Controller.TIME_SEC_SINCE_GO -- seconds, reset to 0.0 each go loop
Controller.FRAMES_ABSOLUTE   -- frames, continuously increasing
Controller.FRAMES_SINCE_GO   -- frames, reset to 0 each go loop

If none of these flags is set, the value is:

Controller.TIME_INDEPENDENT -- No temporal variables.

When the eval methods (during_go_eval and between_go_eval) are
called, attributes are set depending on the temporal variables
used:

temporal_variable   attribute set
-----------------   -------------
TIME_SEC_ABSOLUTE   self.time_sec_absolute
TIME_SEC_SINCE_GO   self.time_sec_since_go
FRAMES_ABSOLUTE     self.frames_absolute
FRAMES_SINCE_GO     self.frames_since_go

Other information:

Instances of Controller are called by instances of the
Presentation class.  during_go_eval() is called during a go()
loop, and between_go_eval() is called by between_presentations()
(during run_forever(), for example).  Before calling these
methods, attributes of the controller are set accoring to
ttribute{temporal_variables}.

Create instance of Controller. 

Arguments:

eval_frequency -- Int, bitwise "or" of flags
temporal_variables -- Int, bitwise "or" of flags
return_type -- Set to type() of the parameter under control

Called by Presentation. Evaluate between runs of the main 'go' loop.

Override this method in subclasses.

Called by Presentation. Evaluate during the main 'go' loop.

Override this method in subclasses.

Call this after updating the values of a controller if it's not evaluated EVERY_FRAME.

Called by Presentation. Get the return type of this controller.