Radial Tree Layout (formerly: Balloon Layout)

This chapter describes the major API changes to the RadialTreeLayout (formerly called BalloonLayout) introduced with yFiles for HTML 3.0 and how to migrate from the older version.

Like all major layout algorithms, the class no longer inherits from MultiStageLayout, but implements ILayoutAlgorithm directly. The layout stages are now managed by a LayoutStageStack, which can be obtained via the layoutStages property; see the migration chapter Layout Stages and Multi-Stage Layouts for more details.

Renamed, Moved, and Removed Classes and Members

The following table lists the renamed, moved, and removed classes and members of the major classes of the RadialTreeLayout.

Renamed, moved, and removed members of classes related to the RadialTreeLayout (classes are bold)
yFiles for HTML 2.6	yFiles for HTML 3.0	Remarks
BalloonLayout	RadialTreeLayout
Properties in class RadialTreeLayout
comparer	removed	Use childOrder instead
componentLayoutEnabled	componentLayout.enabled
considerNodeLabels	nodeLabelPlacement	Has been combined with properties IntegratedNodeLabeling and NodeLabelingPolicy.
fromSketchMode	removed	Use the new enum value FROM_SKETCH instead.
hideGroupsStage	removed	The GroupHidingStage is enabled by default and can be accessed via the stack layoutStages.
hideGroupsStageEnabled	removed
integratedEdgeLabeling	edgeLabelPlacement	Is now enabled by default (value INTEGRATED).
integratedNodeLabeling	nodeLabelPlacement	Has been combined with properties ConsiderNodeLabeling and NodeLabelingPolicy.
interleavedMode	removed	Interleaved placement is automatically activated for nodes that are specified via property interleavedNodes.
labeling	removed	To influence the labeling, use the nodeLabelPlacement and edgeLabelPlacement properties.
labelingEnabled	removed
layoutOrientation	removed	Changing the layout orientation does not make sense for an undirected layout algorithm.
nodeLabelingPolicy	nodeLabelPlacement	Has been combined with properties ConsiderNodeLabeling and IntegratedNodeLabeling.
orientationLayout	removed	Changing the layout orientation does not make sense for an undirected layout algorithm.
orientationLayoutEnabled	removed
parallelEdgeRouterEnabled	removed	Use property Enabled on parallelEdgeRouter instead.
preferredChildWedge	preferredChildSectorAngle
preferredRootWedge	preferredRootSectorAngle
rootNodePolicy	removed	A custom root is now always used if defined in treeRoot.
selfLoopRouterEnabled	removed	Use property Enabled on selfLoopRouter instead.
subgraphLayout	removed	If necessary, the SubgraphLayoutStage can be accessed and enabled via method get<T> of property layoutStages, but this may lead to overlaps.
subgraphLayoutEnabled	removed

BalloonLayoutData	RadialTreeLayoutData<TNode,TEdge,TNodeLabel,TEdgeLabel>
Properties in class RadialTreeLayoutData
abortHandler	removed	A LayoutAbortController is exposed by the LayoutExecutor; see Section Maximum Duration and Aborting of Algorithms for more details.
edgeLabelPreferredPlacement	edgeLabelPreferredPlacements
nodeHalos	nodeMargins
outEdgeComparer	childOrder

Changed Default Values and Behavior Changes

If non-tree graphs are provided as input, the layout algorithm now temporarily reduces them to trees by applying the TreeReductionStage. The non-tree edges are then routed using the router specified via the TreeReductionStage.nonTreeEdgeRouter. The TreeReductionStage used by the RadialTreeLayout is accessible via the property RadialTreeLayout.treeReductionStage.

The from-sketch mode (ordering policy FROM_SKETCH) does no longer take precedence over orders specified via layout data properties childOrder or nodeTypes.

Node labels are now considered by default. To change this behavior, set the nodeLabelPlacement property to the desired value. It is now also easier to place the node labels with GenericLabeling by setting the value to GENERIC.

Edge labels are now placed by default using an integrated edge labeling algorithm. To change this behavior set the edgeLabelPlacement property to the desired value. It is now also easier to place the edge labels with GenericLabeling by setting the value to GENERIC.

The default component arrangement style has been changed to PACKED_CIRCLE. The style can be specified via the ComponentLayout.style property. The ComponentLayout used by the RadialTreeLayout is accessible via the componentLayout property.

The compactnessFactor is now interpreted differently. Larger values now produce more compact layouts. The range of the compactness factor has been changed to the interval between 0 and 1.

Major Changes to Expert API

The changes described in this chapter only affect users who work directly with the LayoutGraph API, such as when writing custom layout algorithms.

Several methods for advanced customization of the layout result have been removed from the API, including calculateChildArrangement and calculateAngles. Overriding these methods should not have been necessary. To customize the preferred sector angles, the callback method getPreferredChildSectorAngle is still available.

The helper class BalloonLayoutNodeInfo has also been removed. It was only necessary and useful during the layout process and when overriding advanced methods that have now been removed.

Tree Layout Radial Layout