Unit Name : QTVRControl
 Comment   : QTVR player control for QT4Delphi
 Author    : George Birbilis
 History   :
  19Sep1998 - first creation
  20Oct1998 - added {$R *.DCR} to link an icon for design-time
  29Nov1998 - adding QTVR manager intercept proc handling (Events)
  17Dec1998 - now using the QTVREvents unit to expose QTVR manager events as
              our events
            - bug-fix: the set_filename method now checks if the
              inherited.set_filename
              just returned without doing anything (was caling QTVRGetQTVRTrack
              passing a nil movie instance!!!)
  18Jan1999 - Added implementation for FOVChange and TriggerHotSpot events
            - now event handler uses the params passed by QT and doesn't ask QT
              again for what is the new value of the param that changed
            - event handler passes by reference the "cancel" param to user's
              handler, so that he can do cancel:=true to cancel the intercepted
              QTVR action (if he returns nothing cancel is false - initially
              set so by the QTVR Manager)
  20Feb1999 - changed {$R *.DCR} to {$R *.RES} to link component's icon into
              the compiled code when having *.DCR files and removing a
              component from the package, when placing it back we get a
              {$R xxxComponent.DCR} in the package's source (.DPK) file... this
              results in a duplicate resource error message when linking the
              package, cause we import the resource for our unit and Delphi
              imports it again for the package (if we let the package to import
              it, the resource would be available only at the design package
              and not at runtime)
  23Feb1999 - overriden CloseMovie to set 'myInstance' (qtvrInstance) field to
              nil, so that we won't try to access a destroyed qtvr instance
            - made property accessor methods safe: now they check for
              myInstance<>nil before using it
            - not overriding setFilename method any more, overriding setMovie
            - In destroy, we're now doing TerminateQTVR only when
              qtvrInited=true (we're also setting qtvrInited=false before
              calling TerminateQTVR)
   7Mar1999 - not using the QuickTime unit any more, but using C_Types &
              qt_MacTypes
  26Jul1999 - changed closeMovie() method accesibility to public from
              protected, since was overriding it from TQTControl and it had it
              as public
   4Apr2000 - fixed type at "write" accessor for property "fieldOfView" (was
              setting the tiltAngle instead of the fieldOfView)
  13Oct2001 - removed any not needed units from the "uses" clauses
   7Nov2001 - added "getViewState" and "setViewState" utility methods
            - added "viewStateCount", "currentViewState", "defaultViewState"
              and "mouseDownViewState" properties
            - added "viewAnimation", "frameAnimation" properties
            - added PalindromeViewFrames, StartFirstViewFrame,
              DontLoopViewFrames, PlayEveryViewFrame, SyncViewToFrameRate,
              PalindromeViews, PlayStreamingViews properties
            - added WrapPan, WrapTilt, CanZoom, ReverseHControl,
              ReverseVControl, SwapHVControl, Translation properties
   8Nov2001 - added ShowDefaultView method
            - added UseDefaultView property (default is false for backwards
              compatibility)
   1Dec2001 - now calling RegisterClass too at the register procedure
   5Dec2001 - renamed "minQTVRTrack" property to "MinQTVRTrack"
            - renamed method "setTheMovie" to "setMovie"
            - converted "var" cancel parameter of events to an "out" parameter
            - "setMovie" method is now protected, assignment to QTMovie
              property is suggested to be used instead of calling "setMovie"
            - "closeMovie" renamed to "CloseMovie"
   6Dec2001 - now using "QTMovie" and "QTMovieController" properties of
              TQTControl instead of the now private field "FMovie" and
              "FMovieController" of that class
  18Dec2001 - now AngularUnits are set correctly after loading from saved state
  10Feb2002 - now AngularUnits property is set before PanAngle, TitleAngle and
              FieldOfView properties' values when loading a new movie
  25Feb2002 - fixed-bug: at "setQTVRTrack" now installing an intercept proc for
              HotSpot triggering events
            - made "setQTVRTrack" method virtual so that an ancestor component
              can add more events' interception code
            - added "GetVRWorld" public method
            - added "NodeID" property and protected methods
              "getNodeID" and "setNodeID"
            - added "goToDefaultNode" and "goToPreviousNode" public methods
            - added "CurrentNodeType" property and protected method
              "getCurrentNodeType"
            - added "GetNodeInfo" public method
            - at "InterceptProc" calling "Editor.modified" if Editor<>nil (that
              is if we're in design mode inside the Delphi IDE) and if not in
              loading state
            - added "triggerHotSpot" function (returns boolean if successful)
  13Apr2002 - removed {$R *.RES}, now using a .DCR file, linked into the delphi
              package, not into this unit
            - fixed TriggerHotSpotEvent, now working OK