Class LabelCacheImpl

  • All Implemented Interfaces:

    public class LabelCacheImpl
    extends Object
    implements LabelCache
    Default LabelCache Implementation.

    The label cache sports a number of features that are enabled depending on the programmatic configuration and the TextSymbolizer options.

    The basic functionality of the label cache consist in finding the best label position for each Feature according to the TextSymbolizer specifications, and drawing it, provided it does not overlap with other labels.

    This basic behaviour can be customised in a number of ways.


    TextSymbolizer.getPriority() OGC Expression controls a label priority.

    A label with high priority will be drawn before others, increasing its likeliness to appear on the screen

    jeichar, dblasby, Andrea Aime - OpenGeo
    • Field Detail


        public static boolean DISABLE_LETTER_LEVEL_CONFLICT

        public double DEFAULT_PRIORITY

        public static final int[] DEFAULT_DISPLACEMENT_ANGLES

        public static double MIN_CURVED_DELTA
        The angle delta at which we switch from curved rendering to straight rendering
    • Constructor Detail

      • LabelCacheImpl

        public LabelCacheImpl()
    • Method Detail

      • enableLayer

        public void enableLayer​(String layerId)
        Description copied from interface: LabelCache
        Enable a layer after being disabled. If startLayer is called this does not need to be called as start layer implicitely activates the layer.
        Specified by:
        enableLayer in interface LabelCache
        layerId - layer to activate.
      • stop

        public void stop()
        Description copied from interface: LabelCache
        Tells the cache to stop labelling.
        Specified by:
        stop in interface LabelCache
      • start

        public void start()
        Description copied from interface: LabelCache
        Called by renderer to indicate that the rendering process is starting.
        Specified by:
        start in interface LabelCache
        See Also:
      • clear

        public void clear()
        Description copied from interface: LabelCache
        Clears the cache completely
        Specified by:
        clear in interface LabelCache
      • clear

        public void clear​(String layerId)
        Description copied from interface: LabelCache
        Clears the cache of all information relating to the layer identified.
        Specified by:
        clear in interface LabelCache
        layerId - id of the layer
      • disableLayer

        public void disableLayer​(String layerId)
        Description copied from interface: LabelCache
        Leaves the label information in the cache but ignores it when calculating what labels are drawn.
        Specified by:
        disableLayer in interface LabelCache
        layerId - id of the layer to disable.
      • startLayer

        public void startLayer​(String layerId)
        Description copied from interface: LabelCache
        Called by renderer to indication the start of rendering a layer. Will add the layer to the set of active layers.
        Specified by:
        startLayer in interface LabelCache
        layerId - an id for the layer
        See Also:
      • getPriority

        public double getPriority​(TextSymbolizer symbolizer,
                                  Feature feature)
        get the priority from the symbolizer its an expression, so it will try to evaluate it: 1. if its missing --> DEFAULT_PRIORITY 2. if its a number, return that number 3. if its not a number, convert to string and try to parse the number; return the number 4. otherwise, return DEFAULT_PRIORITY
      • put

        public void put​(String layerId,
                        TextSymbolizer symbolizer,
                        Feature feature,
                        LiteShape2 shape,
                        NumberRange scaleRange)
        Description copied from interface: LabelCache
        Puts a Label in the cache.
        Specified by:
        put in interface LabelCache
        layerId - id indicating the layer the feature is part of
        symbolizer - The symbolizer containing the style information
        feature - the feature that has the information required for the symbolizer to calculate the required render information.
        shape - the shape to be labeled. This is in screen coordinates.
        scaleRange - the scaleRange that the symbolizer is legal
        See Also:
        LabelCache.put(String,TextSymbolizer,Feature, LiteShape2,NumberRange)
      • put

        public void put​(Rectangle2D area)
        Description copied from interface: LabelCache
        Reserve the provided geometry prior to sorting out where labels can go.

        This facility is used to reserve an area so that labels do not end up overlapping on screen constructs like scalebars or north arrows etc...

        Specified by:
        put in interface LabelCache
        area - The Area of the screen to reserve (in screen coordinates)
      • orderedLabels

        public List<LabelCacheItem> orderedLabels()
        Return a list with all the values in priority order. Both grouped and non-grouped
        Specified by:
        orderedLabels in interface LabelCache
        list with all values in priority order
      • getActiveLabels

        public List<LabelCacheItem> getActiveLabels()
        Returns a list of all active labels
      • clipLineString

        public MultiLineString clipLineString​(LineString line)
        try to be more robust dont bother returning points

        This will try to solve robustness problems, but read code as to what it does. It might return the unclipped line if there's a problem!

      • clipPolygon

        public MultiPolygon clipPolygon​(Polygon poly,
                                        Polygon bbox,
                                        Envelope displayGeomEnv)
        try to do a more robust way of clipping a polygon to a bounding box. This might return the orginal polygon if it cannot clip TODO: this is a bit simplistic, there's lots more to do.
        a MutliPolygon
      • processNodes

        public List<LineString> processNodes​(List<LineString> edges,
                                             Map<Coordinate,​List<LineString>> nodes)
        pull a line from the list, and: 1. if nothing connects to it (its issolated), add it to "result" 2. otherwise, merge it at the start/end with the LONGEST line there. 3. remove the original line, and the lines it merged with from the hashtables 4. go again, with the merged line
      • addRenderListener

        public void addRenderListener​(RenderListener listener)
        adds a listener that responds to error events of feature rendered events.
        listener - the listener to add.
        See Also: