TGraphLink.md

TGraphLink = class(TGraphObject)

This class represents links (edges) of a graph.

Properties

In addition to the properties of the TGraphObject class, the TGraphLink class has the following extra properties:

• public Polyline: TPoints
  Gets or sets the endpoint coordinates of the link's line segments.

• public Points[Index: Integer]: TPoint
  Determines the coordinate of a start, break, or end point of the link, by specifying its zero-based index.

• public PointCount: Integer read fPointCount (read-only)
  Gets the number of points in the Polyline and Points properties of the link.

• published TextPosition: Integer default -1
  Determines the index of the line segment, where the caption of the link appears parallel to it. A value of -1 for this property, indicates the longest line segment.

• published TextSpacing: Integer default 0
  Determines the distance between the caption of the link and the line segment parallel to it.

• published BeginStyle: TLinkBeginEndStyle default lsNone
TLinkBeginEndStyle = (lsNone, lsArrow, lsArrowSimple, lsCircle, lsDiamond)
  Specifies the begin style of the link.

  Value	Shape at the starting point of the link
  lsNone	Nothing
  lsArrow	An open-headed arrow
  lsArrowSimple	A simple arrow
  lsCircle	A circle
  lsDiamond	A diamond

• published BeginSize: Byte default 6
  Determines the size of the BeginStyle shape of the link.

• published EndStyle: TLinkBeginEndStyle default lsArrow
TLinkBeginEndStyle = (lsNone, lsArrow, lsArrowSimple, lsCircle, lsDiamond)
  Specifies the end style of the link.

  Value	Shape at the ending point of the link
  lsNone	Nothing
  lsArrow	An open-headed arrow
  lsArrowSimple	A simple arrow
  lsCircle	A circle
  lsDiamond	A diamond

• published EndSize: Byte default 6
  Determines the size of the EndStyle shape of the link.

• published LinkOptions: TGraphLinkOptions default []
TGraphLinkOptions = (gloFixedStartPoint, gloFixedEndPoint, gloFixedBreakPoints, gloFixedAnchorStartPoint, gloFixedAnchorEndPoint)
  Specifies the behavioral attributes of the node.

  Value	Description
  gloFixedStartPoint	The starting point of the link cannot be changed.
  gloFixedEndPoint	The ending point of the link cannot be changed.
  gloFixedBreakPoints	The breakpoints of the link cannot be changed.
  gloFixedAnchorStartPoint	If the starting point of the link is attached to a node, the point is fixed to the center of the node. If the starting point of the link is attached to a link, the point is fixed to the innermost breakpoint or line segment of the other link.
  gloFixedAnchorEndPoint	If the ending point of the link is attached to a node, the point is fixed to the center of the node. If the ending point of the link is attached to a link, the point is fixed to the innermost breakpoint or line segment of the other link.

  See also the Options property of TGraphObject class.

• public Source: TGraphObject
  Determines the graph object to which the starting point of the link is attached.

• public Target: TGraphObject
  Determines the graph object to which the ending point of the link is attached.

Methods

In addition to the methods of the TGraphObject class, the TGraphLink class has the following extra methods:

• constructor CreateNew(AOwner: TSimpleGraph; ASource: TGraphObject; const Pts: array of TPoint; ATarget: TGraphObject);
  Initiates a new instance of the link class.

  Parameter	Description
  AOwner	The TSimpleGraph instance that owns this link
  ASource	The GraphObject instance that is the source of a connection, or nil for none
  Pts	The control points of the link
  ATarget	The GraphObject instance that is the target of a connection, or nil for none

  A EGraphInvalidOperation exception will be raised if instance cannot be created.

• function AddPoint(const Pt: TPoint): Integer;
  Adds a point to the end of the Points list.

  Parameter	Description
  Pt	The coordinate of the new point

  Returns the index of the newly added point in the Points list.

• procedure InsertPoint(Index: Integer; const Pt: TPoint);
  Adds a point at a specified index of the Points list .

  Parameter	Description
  Index	The index of the new point in the Points list
  Pt	The coordinate of the new point

• procedure RemovePoint(Index: Integer);
  Removes the point at the specified index of the Points list.

  Parameter	Description
  Index	The index of the point in the Points list

• function IndexOfPoint(const Pt: TPoint; Neighborhood: Integer = 0): Integer;
  Finds index of a point in the Points list.

  Parameter	Description
  Pt	The coordinate of the point
  Neighborhood	The proximity tolerance as radius in pixels

  Returns the index of the point if the point is found; otherwise, returns -1.

• function AddBreakPoint(const Pt: TPoint): Integer;
  Inserts a breakpoint at the specified point on (or close to) a line segment of the link.

  Parameter	Description
  Pt	The coordinate of the point

  Returns the index of the inserted point in the Points list, or -1 if the point was not close to any line segment.

• function NormalizeBreakPoints(Options: TLinkNormalizeOptions): Boolean;
  Passes through the Points list and deletes the ineffectual ones.

  Parameter	Description
  Options	Determines how to select the candidate points for removal

  The Options parameter can have a combination of the following values:

  Value	Meaning
  lnoDeleteSamePoint	Remove the break points that produce tiny line segments
  lnoDeleteSameAngle	Remove the break points that produce parallel line segments

  Returns true if any point is removed; otherwise, returns false.

• function IsFixedPoint(Index: Integer; HookedPointsAsFixed: Boolean): Boolean;
  Determines whether the point at the specified index of the Points list, is fixed.

  Parameter	Description
  Index	The index of the point in the Points list
  HookedPointsAsFixed	Specifies whether the points attached to other graph objects should be considered fixed

  Returns true if the point is a fixed point; otherwise, returns false.

• function IsHookedPoint(Index: Integer): Boolean;
  Determines whether the point at the specified index of the Points list is attached to a graph object.

  Parameter	Description
  Index	The index of the point in the Points list

  Returns true if the point is attached to a graph object; otherwise, returns false.

• function HookedObjectOf(Index: Integer): TGraphObject;
  Gets the graph object to which the point at the specified index of the Points list is attached.

  Parameter	Description
  Index	The index of the point in the Points list

  Returns the graph object to which the point is attached, or nil if the point is attached to none.

• function HookedIndexOf(GraphObject: TGraphObject): Integer;
  Gets the index of a point in the Points list, to which a specified graph object is attached.

  Parameter	Description
  GraphObject	A TGraphObject instance

  Returns the index of the point, or -1 if the graph object is not attached to the link.

• function HookedPointCount: Integer;
  Returns the number of points in the Points list, which are attached to a graph object.

• function CanHook(Index: Integer; GraphObject: TGraphObject): Boolean;
  Examines whether the point at the specified index of the Points list can be attached to a given graph object.

  Parameter	Description
  Index	The index of the point in the Points list
  GraphObject	A TGraphObject instance

  Returns true if the link can be attached to the graph object at the specified point; otherwise, returns false.

• function Hook(Index: Integer; GraphObject: TGraphObject): Boolean;
  Attaches the point at the specified index of the Points list to a given graph object.

  Parameter	Description
  Index	The index of the point in the Points list
  GraphObject	A TGraphObject instance

  Returns true if the link could attach to the graph object at the specified point; otherwise, returns false.

• function Unhook(Index: Integer): Boolean; overload;
  Detaches the point at the specified index of the Points list from any graph object.

  Parameter	Description
  Index	The index of the point in the Points list

  Returns true if the link was attached to a graph object at the specified point; otherwise, returns false.

• function Unhook(GraphObject: TGraphObject): Integer; overload;
  Detaches the link from a given graph object.

  Parameter	Description
  GraphObject	A TGraphObject instance

  Returns the index of the attached point if the link was attached to the graph object; otherwise, returns -1.

• function CanLink(ASource, ATarget: TGraphObject): Boolean;
  Examines whether the link can connect two graph objects.

  Parameter	Description
  ASource	A TGraphObject instance as the source of the connection
  ASource	A TGraphObject instance as the target of the connection

  Returns true if the link can connect the graph objects; otherwise, returns false.

• function Link(ASource, ATarget: TGraphObject): Boolean;
  Connects two graph objects.

  Parameter	Description
  ASource	A TGraphObject instance as the source of the connection
  ASource	A TGraphObject instance as the target of the connection

  Returns true if the link could connect the graph objects; otherwise, returns false.

• function CanMove: Boolean;
  Returns true if all the points in the Points list of the link can move freely.

• function Rotate(const Angle: Double; const Origin: TPoint): Boolean;
  Rotates the link by an angle around a specified point.

  Parameter	Description
  Angle	The angle of rotation in radians
  Origin	The coordinate of the center of rotation

  Returns true if the link is rotated; otherwise, returns false.

• function Scale(const Factor: Double): Boolean;
  Scales the link by a scaling factor.

  Parameter	Description
  Factor	The scaling factor

  Returns true if the link is scaled; otherwise, returns false.

• procedure Reverse;
  Reverses the direction of the link.