LinkComp(3U)						    InterViews Reference Manual 					      LinkComp(3U)

NAME

       LinkComp, LinkView, PSLink - component subject, view, and PostScript external representation for lines with connectable endpoints

SYNOPSIS

       #include <Unidraw/Components/link.h>

DESCRIPTION

       LinkComp is a GraphicComp defining a line with two pins on each end.  The line's endpoints will always coincide with the pins, even if they
       are moved, thereby maintaining a graphical link between the objects to which it is connected.  LinkComp uses an Line graphic to define  its
       initial	geometry  and graphical attributes.  LinkView is a GraphicView for displaying the link.  PSLink is a PostScriptView that external-
       izes the subject's information in PostScript form.

LINKCOMP PUBLIC OPERATIONS

       LinkComp(Line* = nil)
	      The constructor takes an optional line graphic to define its initial appearance.

       virtual void Interpret(Command*)
       virtual void Uninterpret(Command*)
	      In addition to (un)interpreting the commands GraphicComp (un)interprets, LinkComp also (un)interprets DeleteCmd and CutCmd by  pass-
	      ing these commands to its pins for (un)interpretation.

       virtual void Update()
	      When the LinkComp's pins move to maintain connectivity, LinkComp will reorient the line so that its endpoints and the pins coincide.

       virtual void First(Iterator&)
       virtual void Last(Iterator&)
       virtual void Next(Iterator&)
       virtual void Prev(Iterator&)
       virtual boolean Done(Iterator)
       GraphicComp* GetComp(Iterator)
       void SetComp(GraphicComp*, Iterator&)
	      LinkComp	redefines  GraphicComp's traversal operations to make its pins accessible to the Unidraw library.  Thus Unidraw can deter-
	      mine the connectors that belong to the component and call its Update operation only once for efficiency.	 The  traversal  does  not
	      include the line.

       Line* GetLine()
	      Return the Line graphic that defines the link's attributes.  GetLine is simply a more specific form of the GetGraphic operation.

       void GetConnectors(Connector*&, Connector*&)
	      Return the LinkView's pins, which are stored in the _conn1 and _conn2 protected members.

LINKVIEW PUBLIC OPERATIONS

       LinkView(LinkComp* = nil)
	      Create an LinkView, optionally supplying the subject.

       virtual Manipulator* CreateManipulator(
	  Viewer*, Event&, Transformer*, Tool*
       )

       virtual void InterpretManipulator(Manipulator*)
	      LinkView	redefines  its response to manipulation with a GraphicCompTool.  The user clicks to specify the first endpoint of the link
	      and then drags to position the remaining endpoint.  (Up)clicking on an existing connector will establish a connection between it and
	      the  LinkComp's  first (second) pin.  LinkView uses a ConnectManip to produce a gravitational attraction between existing connectors
	      and the second pin as the user drags to position it.  The endpoints will not be constrained by  gravity.	 LinkView  will  use  Con-
	      nectCmds	to  connect the pin(s) to their target(s). Pin(s) connected in this way will receive floating mobility; unconnected pin(s)
	      will be fixed.

       virtual void First(Iterator&)
       virtual void Last(Iterator&)
       virtual void Next(Iterator&)
       virtual void Prev(Iterator&)
       virtual boolean Done(Iterator)
       GraphicView* GetView(Iterator)
       void SetView(GraphicView*, Iterator&)
	      LinkView redefines GraphicView's traversal operations to make its pins accessible to the Unidraw library.  Thus Unidraw  can  deter-
	      mine the connectors that belong to the component, for example, to support ConnectManip's gravitational attraction effect.

       virtual void GetEndpoints(Coord&, Coord&, Coord&, Coord&)
	      Return the link's endpoints, in canvas coordinates.

       LinkComp* GetLinkComp()
	      Return the subject.

LINKVIEW PROTECTED OPERATIONS

       virtual void CreateHandles()
	      LinkView redefines CreateHandles to use a RubberHandles object with two handles, one at each endpoint of the link.

       Line* GetLine()
	      Return the line that LinkView draws between its pins.

       virtual LinkComp* NewSubject(Line*)
	      A  helper  function  that creates a LinkComp subject with the given line graphic. This function produces the proper subject when the
	      GraphicCompTool's manipulator is interpreted.  Subclasses can redefine this operation to return a LinkComp subclass, thus  eliminat-
	      ing the need to reimplement InterpretManipulator.

       Manipulator* CreateLinkCompManip(
	   Viewer*, Event&, Transformer*, Tool*
       )

       Command* InterpretLinkCompManip(Manipulator*)
	      Helper functions that CreateManipulator and InterpretManipulator use to create and interpret the manipulator for GraphicCompTool.

PSLINK PUBLIC OPERATIONS

       PSLink(LinkComp* = nil)
	      Construct a PostScript external representation of the given subject, if any.

SEE ALSO

       Event(3I),  Graphic(3U), GraphicComp(3U), GraphicCompTool(3U), GraphicView(3U), Grid(3U), PinComp(3U), PostScriptView(3U), Transformer(3I),
       align(3U), edit(3U), manips(3U)

Unidraw 							  22 January 1991						      LinkComp(3U)