The Bus Layout uses generic parameters, common to other graph layouts, and specific parameters applicable in bus layouts only. Refer to the following sections for general information on parameters among the graph layouts:

The Bus Layout parameters are described in detail in this topic under:

The IlvBusLayout class supports generic parameters defined in the IlvGraphLayout class. The following comments describe the particular way in which these parameters are used by this subclass:

The layout algorithm uses the layout region setting (either your own or the default setting) to control the size and the position of the graph drawing. All three ways of specifying the layout region are available for this subclass. (For a description of this parameter in the IlvGraphLayout class, see Layout Region.)

Remember that if you are using the default settings, there must be a view (an instance of IlvView) attached to the grapher. If no view is attached, and no layout region is explicitly specified, the layout algorithm cannot produce reasonable results.

If a layout region is specified, this region is used. If no layout region is specified but a view is attached, the size and position of the graph drawing is computed to approximately fill the view.

The size of the layout is chosen with respect to the layout region (see Figure 4.42). The height of the layout region is not taken into account. The height of the layout will be smaller or larger, depending on the number of nodes, the size of the nodes, and the other specified parameters.

The layout algorithm does not reshape the links that are specified as fixed. (For more information on link parameters in the IlvGraphLayout class, see Preserve Fixed Links.)

The layout algorithm does not move the nodes that are specified as fixed. (For more information on node parameters in the IlvGraphLayout class, see Preserve Fixed Nodes.)

The following parameters are specific to the IlvBusLayout class:

The order parameter specifies how to arrange the nodes.

To specify the ordering option for the nodes, use the method:

The valid values are:

To obtain the current value, use the method:

The index is an integer value associated with a node and is specified using the method:

The values of the indexes cannot be negative. To obtain the current index of a node, use the method:

If no index is specified for the node, the value NoIndex is returned.

The ordering options for the Bus Layout are illustrated in Table 4.5.

To represent bus topologies, the algorithm reshapes a special node, called the “bus node”, and gives it a “serpent” form. This bus node must be an instance of the IlvPolyline class. Before performing the layout, you must create this object and add it to the grapher as a node. (The number of points in the object you create is not important.) Then, you must specify the node as “bus node” using the method:

To obtain the current selection for the bus node, use the method:

You can also use subclasses of IlvPolyline. (See the code provided in Code Sample.)

When the layout algorithm moves the nodes, straight-line links, such as instances of IlvLinkImage, will automatically “follow” the new positions of their end nodes. If the grapher contains other types of links (for example, IlvPolylineLinkImage or IlvDoubleSplineLinkImage), the shape of the link may not be appropriate because the intermediate points of the link will not be moved. In this case, you can ask the layout algorithm to automatically remove all the intermediate points of the links (if any). To do this, the following method is provided:

The valid values are:

To obtain the current choice, use the following method:

Figure 4.42 illustrates the dimensional parameters used in the Bus Layout algorithm. These parameters are:

This parameter represents the horizontal distance between two nodes. To specify the horizontal offset, use the method:

To obtain the current value, use the method:

This parameter represents the vertical distance between a row of nodes and the next horizontal segment of the bus node. To specify this parameter, use the method:

To obtain the current value, use the method:

This parameter represents the vertical distance between a row of nodes and the previous horizontal segment of the bus node. To specify this parameter, use the method:

To obtain the current value, use the method:

This parameter represents the offset distance between the layout region and the bounding rectangle of the layout. To specify this parameter, use the method:

To obtain the current value, use the method:

On the odd horizontal levels (first, third, fifth, and so on) of the bus starting from the top, this parameter represents the offset distance between the left side of the first node on the left and the left side of the bus object.

On the even horizontal levels (second, fourth, sixth, and so on) of the bus starting from the top, this parameter represents the offset distance between the right side of the last node on the right and the right side of the bus object. (See Figure 4.42 for an illustration of the margin-on-bus parameter.)

To specify this parameter, use the method:

To obtain the current value, use the method: