Start angle
If you want to rotate a balloon layout, you can modify
the start angle of the layout. This is the angle where the first child
node is placed at the root. All subtrees rotate with this start angle.
The angle spacing value FAST_PROPORTIONAL is
not stable with respect to the start angle: the layout can change
considerably when you change the start angle. The other angle spacing
values are stable: they rotate the entire layout. The start angle
must be 0° - 360°.
To change the start angle:
Use the method setBalloonStartAngle:
treeLayout.setBalloonStartAngle(90);
Angle range
Normally, child nodes are placed all around their parent
node; they occupy an angle range of 360° around the parent. It
is possible to limit the angle range available for child nodes. In
the following figure, the angle range for child nodes is 360°
degrees on the left, 270° in the middle and 180° on the
right. You can specify a different angle range for the root, for nodes
that have only leaves, and for inner nodes of the tree.

The effect of the balloon child angle: left: 360,
middle: 270, right: 180
To change the angle ranges:
Use the following methods:
For example:
treeLayout.setBalloonRootChildrenAngle(270);
Disconnected trees
Multiple disconnected trees can be laid out together
by the balloon layout mode. By default, they are arranged in a sequence
according to the flow direction of the layout. As an alternative,
you can choose the generic disconnected graph spacing. For details,
see Layout of connected components (TL). Another
alternative, as for radial layout mode, is to introduce an invisible
root. In this case, the balloons are arranged around the invisible
root.
To add an invisible root to the layout:
Use the method setInvisibleRootUsed:
layout.setInvisibleRootUsed(true);