Subclassing the default labeling model

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The default labeling model IlvDefaultLabelingModel is a subclass of IlvLabelingModel . It has certain properties that may not be suitable for your application:

Only objects of type IlvLabel and IlvZoomableLabel are considered labels.
Only objects of type IlvLine, IlvPolyline, and IlvLinkImage are considered polyline obstacles.
All other objects are considered rectangular obstacles.

It is easy to change these properties by subclassing IlvDefaultLabelingModel . For instance, if you use only labels of class MySpecialLabel , you can override the method isDefaultLabelClass :

public boolean isDefaultLabelClass(Object obj)
{
    return (obj instanceof MySpecialLabel);
}

If you want some objects to be completely ignored, make sure they are not considered as labels or obstacles. To avoid considering objects of class IgnorableGraphic as obstacles, you can override the method isObstacle :

public boolean isDefaultObstacleClass(Object obj)
{
    return super.isDefaultObstacleClass(obj) &&
           !(obj instanceof IgnorableGraphic);
}

Note

Instead of overriding isDefaultLabelClass and isDefaultObstacleClass , you can also specify which objects are labels and obstacles by using the methods setLabel and setObstacle , as illustrated in Labels and obstacles in Java.

Some obstacles do not have a rectangular shape. For simplicity and speed, the overlap value is based on the bounding box of normal obstacles. Hence the default labeling model may compute overlaps in situations where in fact there are no overlaps, because the bounding box is usually a little larger than the area that is really covered by the obstacle. You can correct this by overriding the method getOverlapValue by implementing a more precise (but also more complex) overlap test:

public double getObstacleOverlap(
    Object label, IlvRect labelBBox,
    Object obstacle, IlvRect obstacleBBox,
    float minDist)
  {
    ... complex calculation of the overlap considering the precise shape of
    ... the obstacle. If the label is closer than minDist to the obstacle,
    ... it should be considered as overlap
    ...
    if (hasOverlap)
        return a value proportional to the overlap;
    else
        return 0.0;
   }

Since the default labeling model IlvDefaultLabelingModel implements the IlvLabelingModelWithRotation interface, you can similarly override all overlap methods that have a rotation angle parameter for the labels. See The IlvLabelingModelWithRotation Interface.

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Defining your own labeling model