/*
 *    GeoTools - The Open Source Java GIS Toolkit
 *    http://geotools.org
 *
 *    (C) 2011, Open Source Geospatial Foundation (OSGeo)
 *    (C) 2008, Open Geospatial Consortium Inc.
 *    
 *    All Rights Reserved. http://www.opengis.org/legal/
 */
package org.opengis.style;

import org.opengis.annotation.Extension;
import org.opengis.filter.expression.Expression;
import org.opengis.annotation.XmlElement;


/**
 * Indicate that one of a few predefined shapes will be drawn at the points of the geometry.
 *
 *
 * @source $URL: http://svn.osgeo.org/geotools/trunk/modules/library/opengis/src/main/java/org/opengis/style/Mark.java $
 * @version <A HREF="http://www.opengeospatial.org/standards/symbol">Symbology Encoding Implementation Specification 1.1.0</A>
 * @author Open Geospatial Consortium
 * @author Johann Sorel (Geomatys)
 * @author Chris Dillard (SYS Technologies)
 * @since GeoAPI 2.2
 */
@XmlElement("Mark")
public interface Mark extends GraphicalSymbol {

    /**
     * Returns the expression whose value will indicate the symbol to draw.
     * The WellKnownName element gives the well-known name of the shape of the mark.
     * Allowed values include at least “square”, “circle”, “triangle”, “star”, “cross”, and “x”,
     * though map servers may draw a different symbol instead if they don't have a shape for all
     * of these. The default WellKnownName is “square”. Renderings of these marks may be
     * made solid or hollow depending on Fill and Stroke elements.
     *
     * if the WellKnowname is null, check the ExternalMark before using the default square
     * symbol.
     *
     * Both WellKnowName and ExternalMark canot be set, but both can be null.
     * If none are set then the default square symbol is used.
     *
     * @return Expression or null
     */
    @XmlElement("WellKnownName")
    Expression getWellKnownName();

    /**
     * The alternative to a WellKnownName is an external mark format.
     * See {@link ExternalMark} for details.
     *
     * Both WellKnowName and ExternalMark cannot be set, but both can be null.
     * If none are set then the default square symbol is used.
     *
     * @return ExternalMark or null
     */
    ExternalMark getExternalMark();

    /**
     * Returns the object that indicates how the mark should be filled.
     * Null means no fill.
     * @return Fill or null
     */
    @XmlElement("Fill")
    Fill getFill();

    /**
     * Returns the object that indicates how the edges of the mark will be
     * drawn.  Null means that the edges will not be drawn at all.
     *
     * @return stroke or null
     */
    @XmlElement("Stroke")
    Stroke getStroke();
    
    /**
     * calls the visit method of a StyleVisitor
     *
     * @param visitor the style visitor
     */
    @Extension
    Object accept(StyleVisitor visitor, Object extraData);

}