/*$************************************************************************************************
 **
 ** $Id: FeatureLayer.java 1122 2007-11-24 18:49:16Z desruisseaux $
 **
 ** $URL: https://geoapi.svn.sourceforge.net/svnroot/geoapi/tags/2.1.1/geoapi/src/main/java/org/opengis/feature/display/canvas/FeatureLayer.java $
 **
 ** Copyright (C) 2005 Open GIS Consortium, Inc.
 ** All Rights Reserved. http://www.opengis.org/legal/
 **
 *************************************************************************************************/
package org.opengis.feature.display.canvas;

// OpenGIS direct dependencies
import org.opengis.feature.FeatureCollection;
import org.opengis.sld.FeatureStyle;


/**
 * Abstract base class for a grouping of features drawn on a Canvas.  Each
 * instance of this interface has a reference to a collection of features to
 * draw and a style to draw those features with.  Also, each
 * {@code FeatureLayer} has a Z-order value that indicates the order in
 * which features are drawn on the {@link FeatureCanvas}.  Lower numbers
 * draw first.
 * <p>
 * The current style and the Z-order are changeable at runtime, so consumers of
 * {@code FeatureLayer} objects must add listeners to know if they have
 * been changed.
 *
 * @author Chris Dillard (SYS Technologies)
 * @since GeoAPI 2.0
 */
public interface FeatureLayer {
    /**
     * Returns the collection of features that will be portrayed in this layer.
     * A null value is allowed and indicates that nothing will be drawn.
     */
    FeatureCollection getFeatureCollection();

    /**
     * Returns the style to apply to features in this layer.  A null value is
     * allowed, and indicates that the features should not be drawn.
     */
    FeatureStyle getStyle();

    /**
     * Sets the style that will be applied to features in this layer.
     */
    void setStyle(FeatureStyle style);

    /**
     * Returns the minimum z-order level that this layer can be moved to.
     */
    double getMinimumLevel();

    /**
     * Returns the maximum z-order level that this layer can be moved to.
     */
    double getMaximumLevel();

    /**
     * Sets the current z-order level of this layer.
     *
     * @throws IllegalArgumentException If the level is outside the allowable
     *   range.
     */
    void setLevel(double level) throws IllegalArgumentException;

    /**
     * Returns the current z-order level of this layer.
     */
    double getLevel();

    /**
     * Allows an object to register for events when one of the mutable
     * properties of this layer has changed.  A {@code FeatureCanvas}
     * may, for example, use this to receive notification when the style
     * has changed.
     */
    void addFeatureLayerListener(FeatureLayerListener ll);

    /**
     * Removes a listener that was previously added with the
     * <code>{@link #addFeatureLayerListener addFeatureLayerListener}(ll)</code>
     * method.
     */
    void removeFeatureLayerListener(FeatureLayerListener ll);
}
