-- File:	AIS_TangentRelation.cdl
-- Created:	Thu Dec  5 10:43:26 1996
-- Author:	Jean-Pierre COMBE/Odile Olivier
--		<odl@sacadox.paris1.matra-dtv.fr>
---Copyright:	 Matra Datavision 1996

class TangentRelation from AIS inherits Relation from AIS
    	---Purpose: A framework to display tangency constraints between
    	-- two or more Interactive Objects of the datum type.
    	-- The datums are normally faces or edges.
uses Shape                 from TopoDS,
     Presentation          from Prs3d,
     PresentationManager3d from PrsMgr,
     Selection             from SelectMgr,
     Pnt                   from gp,
     Dir                   from gp,
     Projector             from Prs3d,
    Transformation        from Geom,
     PresentationManager2d from PrsMgr,
     GraphicObject         from Graphic2d,    
     Plane                 from Geom

is
    Create (aFShape     : Shape          from TopoDS;
    	    aSShape     : Shape          from TopoDS;
	    aPlane      : Plane          from Geom;
    	    anExternRef : Integer        from Standard = 0)
	    ---Purpose:  TwoFacesTangent or TwoEdgesTangent relation
    returns mutable TangentRelation from AIS;
    	---Purpose: Constructs an object to display tangency constraints.
    	-- This object is defined by the first shape aFShape, the
    	-- second shape aSShape, the plane aPlane and the index anExternRef.
    	-- aPlane serves as an optional axis.
    	-- anExternRef set to 0 indicates that there is no relation.
    
    ExternRef(me: mutable) returns Integer from Standard 
    is static;
    	---Purpose: Returns the external reference for tangency.
    	-- The values are as follows:
    	-- -   0 - there is no connection;
    	-- -   1 - there is a connection to the first shape;
    	-- -   2 - there is a connection to the second shape.
    	--   This reference is defined at construction time.
    
    SetExternRef(me: mutable;aRef : Integer from Standard)
    is static;
    	---Purpose: Sets the external reference for tangency, aRef.
    	-- The values are as follows:
    	-- -   0 - there is no connection;
    	-- -   1 - there is a connection to the first shape;
    	-- -   2 - there is a connection to the second shape.
    	-- This reference is initially defined at construction time.    

    Compute(me            : mutable;
    	    aPresentationManager: PresentationManager3d from PrsMgr;
    	    aPresentation : mutable Presentation from Prs3d;
    	    aMode         : Integer from Standard= 0) 
    is redefined static private;
    
    Compute(me:mutable;
    	        aProjector: Projector from Prs3d;
                aPresentation: mutable Presentation from Prs3d)
    is redefined static private;     

    Compute(me:mutable;
    	    aPresentationManager: PresentationManager2d from PrsMgr;
            aPresentation: mutable GraphicObject from Graphic2d;
            aMode: Integer from Standard = 0)
    is redefined static private;	    

    Compute(me            : mutable;
    	    aProjector    : Projector from Prs3d;
    	    aTrsf         : Transformation from Geom;
	    aPresentation : mutable Presentation from Prs3d)
    is redefined;
    	---Purpose: computes the presentation according to a point of view
    	--          given by <aProjector>. 
    	--          To be Used when the associated degenerated Presentations 
    	--          have been transformed by <aTrsf> which is not a Pure
    	--          Translation. The HLR Prs can't be deducted automatically
    	--          WARNING :<aTrsf> must be applied
    	--           to the object to display before computation  !!!

-- Methods from SelectableObject

    ComputeSelection(me         : mutable;
    	    	     aSelection : mutable Selection from SelectMgr;
    	    	     aMode      : Integer from Standard)is private;


--
--     Computation private methods
--

    ComputeTwoFacesTangent(me: mutable;
    	    	    	   aPresentation : mutable Presentation from Prs3d)
    is private;
    
    ComputeTwoEdgesTangent(me: mutable;
    	    	    	   aPresentation : mutable Presentation from Prs3d)
    is private;
    

fields

    myAttach      : Pnt   from gp;
    myDir         : Dir   from gp;
    myLength      : Real  from Standard;
    myExternRef   : Integer from Standard;  ---purpose: (0  no attachment,1  attachment with first shape, 2  attachment with second shape)
    
end TangentRelation;