VWLib 1.1 REFERENCE MANUAL INDEX
Modifications from version 1.0.
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1.1 Example Programs
- vwLib is a C++ widget class library for virtual reality applications. It requires both
OGL Performer and CAVElib. The event model used by vwLib is based on an Observer Pattern
in conjuction with a Mediator Pattern as described in "Design Patterns: Elements
of Reusable Object-Oriented Software" by Erich Gamma, et.al. The three primary
abstract base classes are vwSubject, vwObserver and vwMediator. vwWidget (the abstract widget class) inherits publically from
vwSubject. Since all widgets are subclasses of vwWidget, all widgets are in turn
non-abstract vwSubjects (concrete subjects). Concrete
subjects generate events. An event occures when a concrete subject calls the notify() method. All non-abstract subclasses of
vwObserver (concrete observers) which have been attached, via
attach(), to the notifying subject will generate
an update() call. In short, concrete subjects call
notify(). notify() generates an update() in all concrete observers attached to that
particular concrete subject. A subclass of vwMediator (concrete
mediator), manages the subject - observer mappings and handles the event
propogation. The concrete mediator's relationship to concrete subjects (widgets) and
concrete observers is illustrated in the following interaction diagram.
- Normally, an application would have only one concrete mediator managing all of the
widgets. However, it is possible to have multiple concrete mediators handling different
groups of widgets. Each widget can only be associated with a single concrete mediator.
This is also the case with concrete observers. Both widgets and observers require the
concrete mediator as an argument to their respective constructors.
- notify() is not public. It is a protected method
which is called from within the event routines of all but one of the generic widgets. The
generic widgets (direct subclasses of vwWidget) are vwButton, vwSlider, vwIncrementor and vwFrame.
vwFrame does not have an event interface. The public method that generates an event in
vwButtons is setPressed(). The public method that
generates an event in vwSliders is drag(). And the public
methods that generate events in vwIncrementor are increment()
- All widgets have a Performer grouping node assocated with them. pfDCS in the case of
vwButton and vwSlider. pfSCS in the case of vwIncrementor and vwFrame.
- As illustrated in the class diagram, below, widgets can act as both vwSubjects and
vwObservers. The vwRadioButton is a good example of this.
An application can have numerous non-widget concrete observers. Through their update() methods, they may take direct action or act as
intermediaries between an interface and other portions of the application.
- ABSTACT CLASSES
GENERIC WIDGET CLASSES
NON-GENERIC WIDGET CLASSES
INTERFACE CONFIGURATION FILES
- Configuration File