Link connection ports

A connection port is the logical position where a link is attached to a node. Normally, this position is automatically determined by the link layout algorithm. Link connection ports provide a way to modify this behavior by forcing the links into a specific position that will be taken into account by the graph layout algorithm.

By default, connection ports are not visible on a node. However, you can display them by attaching to the view an interactor of type IltMakeLinkInteractor operating in pin mode.

Connection ports can be either directed or undirected. Links attached to a directed connection port originate from a specific direction given by the port, and are drawn either vertically or horizontally, depending on the direction. If the main segment of the link is neither horizontal nor vertical, a short segment is added to the extremity of the link to compensate for this. This is the normal behavior implemented by the direct link style of the link layout algorithm. On the other hand, links coming from an undirected connection port can go in any direction, defined randomly by the layout algorithm. In this case, no additional segment is appended to their extremities.

These two types of connection port are illustrated in the following figures:

A node with four directed connection ports

A node with an undirected link connection port (at the center of the cloud)

A link connection port is defined by the following:

The point on the node where the link should end. This point is specified with two floating point values, fx and fy , ranging between 0 and 1 . These are proportional values, relative to the link connection rectangle.

Note

The connection rectangle is generally represented by the bounding box of the node, except for groups for which this connection rectangle can be the group plinth.
- fx = 0 corresponds to the left side
- fx = 0.5 corresponds to the vertical center line
- fx = 1 corresponds to the right side
- fy = 0 corresponds to the top side
- fy = 0.5 corresponds to the horizontal center line
- fy = 1 corresponds to the bottom
  
  Note
  
  When there is more than one link, and the connection port is a directed one, the link bundling feature of the graph layout makes the link end in the vicinity of this point, not exactly on it.
The direction of the outgoing link. For directed link connection ports, this direction is generally defined by IlvDirection. Top, IlvDirection. Bottom, IlvDirection. Left, and IlvDirection. Right, depending on which side of the node the link starts from. For undirected links, this value is IlvDirection. Center.
Optionally, the distance between two links ending at the same link connection port. Negative values are ignored. This option is generally used to override the distance between two links set for the IltShortLinkLayout instance of a specific port.

When a link connection port is applied to a node, the target point is computed from the values of fx , fy , and the link connection rectangle.

The class IltLinkPort is an enumeration type that defines the following values: Top , Bottom , Left , Right , and Center . The first four values indicate that the link should connect to the center point of the corresponding node side. For example, Left specifies that the link will be attached to the center of the left side of the node. These values apply to directed link ports. The last value, Center , applies to undirected link ports. These values can be customized through CSS as illustrated in Customizing link port configuration in the Styling documentation. You can create your own instances of IltLinkPort by providing specific values to the fx , fy , and direction parameters.

Only the IltShortLinkLayout and IltLinkLayout (when set in short link mode) layout algorithms implement link connection ports. When used in an JViews TGO network component, these layouts use the following optional information through the IltDefaultNodeSideFilter that is installed automatically:

Each node can specify an array of pins as the linksPorts property. If no array is defined, the following set of values is used by default: {IltLinkPort.Top , IltLinkPort.Bottom , IltLinkPort.Left , IltLinkPort.Right} .

For information on how to configure link ports, refer to Customizing link port configuration in the Styling documentation.
Each link can specify the link port to which it will connect at both ends through the fromPort and toPort properties. If no link port is defined, the layout algorithm will select one among those that are allowed.

How to create link connection ports

Create an IltShortLinkLayout algorithm and attach it to the network component .
```
IltShortLinkLayout layout = new IltShortLinkLayout();
...
network.setLinkLayout(layout);
```
This layout algorithm allows you to handle link connection ports. You could also use IltLinkLayout.

Create new link connection ports using IltLinkPort.

...
IltLinkPort port1=
  new IltLinkPort("Right, above middle",1.0f,0.2f,1,0,-1);

Customizing the representation of links

For information on how to configure the link connection ports, refer to Customizing link port configuration in the Styling documentation.

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