Class
HierarchicGroupLayouter
is a
derived variant of the classic HierarchicLayouter that allows to layout
hierarchically organized graphs.
It recursively traverses a given graph bottom-up from the most nested groups to
the top-level nodes and calculates both position and dimension of the group
nodes in the hierarchical layout.
Class HierarchicGroupLayouter knows a number of data provider keys which are used to retrieve supplemental layout data for a graph's elements. The data is bound to the graph by means of a data provider, which is registered using a given look-up key. Table 5.18, “Data provider look-up keys” lists all look-up keys for HierarchicGroupLayouter.
Binding supplemental layout data to a graph is described in the section called “Providing Supplemental Layout Data”.
Table 5.18. Data provider look-up keys
| Key | Element Type | Value Type | Description |
|---|---|---|---|
| GROUP_DPKEY |
Node | boolean | For each node a boolean value indicating whether it is a group node or not. |
| NODE_ID_DPKEY |
Node | Object | For each node an Object that serves as a unique ID. |
| PARENT_NODE_ID_DPKEY |
Node | Object | For each node an Object indicating the group node it belongs to. The Object matches the unique ID of a group node that is in the same graph. |
| GROUP_NODE_INSETS_DPKEY |
Node | Insets | For each group node a java.awt.Insets object that encodes the group node's insets. |
Setup of a graph's hierarchical organization and using the grouping keys (GROUP_DPKEY, NODE_ID_DPKEY, and PARENT_NODE_ID_DPKEY) is described in detail in the section called “Setup for Layout”.
HierarchicGroupLayouter is an extension of the hierarchical layout algorithm. Beyond the options of this layouter, further support for the specific needs of hierarchically organized graphs is provided.
Additional size requirements of group nodes (e.g., special insets or space for
custom labels) can be specified in one of two different ways.
Either a custom implementation of interface
GroupBoundsCalculator can be
set using the method from API Excerpt 5.8, “Customizing insets calculation for group nodes”, or the
default implementation for that interface, class
InsetsGroupBoundsCalculator,
can be used.
API Excerpt 5.8. Customizing insets calculation for group nodes
// Method from class HierarchicGroupLayouter. void setGroupBoundsCalculator(GroupBoundsCalculator gbc)
Choosing the latter alternative additionally requires the use of a data
provider that provides java.awt.Insets objects for each
group node.
The data provider must be registered with the input graph using the key
GROUP_NODE_INSETS_DPKEY.
During layout calculation it is then used by class InsetsGroupBoundsCalculator.
The following yFiles tutorial demo programs demonstrate how to use class HierarchicGroupLayouter in an application context.