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The Hierarchical Layout allows you to specify the level index and the position index of a node.

In CSS

Specify the level and position index of a node with ID “ node1 ” in the following way:

#node1 {
   SpecNodeLevelIndex: "5";
   SpecNodePositionIndex: "33";   
}

In Java™

You specify the level and position index of a graphic node in the following way:

layout.setSpecNodeLevelIndex(node, 5);
layout.setSpecNodePositionIndex(node, 33);

How these indexes are used depends on the graph topology and the additional constraints. For example, the specified level index can be in conflict with some IlvLevelRangeConstraint or IlvSameLevelConstraint. In this case, the constraint priorities determine how the conflict is resolved (see Constraint priorities (HL)). If the incremental mode is enabled, the specified node level and position index are ignored, since the incremental mode tries to preserve old node positions. It is also possible to obtain the indexes of nodes that were calculated during layout.

Calculated level index

The layout algorithm allows you to access the level index that was calculated for a node by a previous layout. Use the method:

int getCalcNodeLevelIndex(Object node)

If the node was never laid out, this method returns -1 . Otherwise, it returns the previous level index of the node.

In an application that specifies layout parameters entirely in Java, the method can be used to specify the level index for the next layout in the following way:

int index = layout.getCalcNodeLevelIndex(node); 
layout.setSpecNodeLevelIndex(node, index);

It ensures that the node is placed at the same level as in the previous layout.

If the graph is detached from the layout algorithm, the calculated level index of a node is set back to -1 .

Note

Be aware of the difference between the methods getCalcNodeLevelIndex and getSpecNodeLevelIndex. The first one returns the level index calculated by the previous layout. The second one returns the specified level index, even if there was no previous layout.

For instance, consider two nodes A and B. Node A has no specified level index and node B has a specified level index 5. Before the first layout, the method getCalcNodeLevelIndex returns -1 for both nodes because the levels have not been calculated yet. However, getSpecNodeLevelIndex returns -1 for A and 5 for B. After the first layout, node A can be placed at level 4. Now, getCalcNodeLevelIndex returns 4 for node A and 5 for node B and getSpecNodeLevelIndex still returns -1 for A and 5 for B.

Calculated position index

The layout algorithm allows you to access the position index within a level that was calculated for a node by a previous layout. Use the method:

getCalcNodePositionIndex

If the node was never laid out, this method returns -1. Otherwise, it returns the previous position index of the node within its level.

To ensure that the node is placed at the same level at the same relative position as in the previous layout, use the following code in an application that specifies layout parameters entirely in Java:

layout.setSpecNodeLevelIndex(node,
    layout.getCalcNodeLevelIndex(node));

This example code works only if the generic connected component layout is disabled and the port sides EAST or WEST are not used in the layout.

If the graph is detached from the layout algorithm, the calculated position index of a node is set back to -1.

Note

Be aware of the difference between the methods getCalcNodePositionIndex and setSpecNodePositionIndex.The first one returns the position index calculated by the previous layout and -1 if there was no previous layout. The second one returns the specified position index even if there was no previous layout. This behavior is similar to the behavior of the specified and calculated level index (see Calculated level index).

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Hierarchical Layout (HL)