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The main module contains the GeoTools public interfaces that are used by other GeoTools modules (and GeoTools applications). Where possible we make use industry standard terms as provided by OGC and ISO standards. The formal GeoTools public api consists of gt-metadata, jts and the gt-main module. The main module contains the default implementations that are available provided to other GeoTools modules using our factory system. Factories are obtained from an appropriate FactoryFinder, giving applications a chance configure the factory used using the Factory Hints facilities. FilterFactory ff = CommonFactoryFinder.getFilterFactory(); Expression expr = ff.add( expression1, expression2 ); If you find yourself using implementation specific classes chances are you doing it wrong: Expression expr = new AddImpl( expression1, expressiom2 );

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/*
 *    GeoTools - The Open Source Java GIS Toolkit
 *    http://geotools.org
 *
 *    (C) 2002-2008, Open Source Geospatial Foundation (OSGeo)
 *
 *    This library is free software; you can redistribute it and/or
 *    modify it under the terms of the GNU Lesser General Public
 *    License as published by the Free Software Foundation;
 *    version 2.1 of the License.
 *
 *    This library is distributed in the hope that it will be useful,
 *    but WITHOUT ANY WARRANTY; without even the implied warranty of
 *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 *    Lesser General Public License for more details.
 *
 */
package org.geotools.styling;

import org.geotools.filter.ConstantExpression;
import org.opengis.filter.expression.Expression;

/**
 * A PointPlacement specifies how a text label is positioned relative to a geometric point.
 *
 * The details of this object are taken from the OGC Styled-Layer Descriptor
 * Report (OGC 02-070) version 1.0.0.:
 *
 * 

 * <xsd:element name="PointPlacement">
 *   <xsd:annotation>
 *     <xsd:documentation>
 *       A "PointPlacement" specifies how a text label should be rendered
 *       relative to a geometric point.
 *     </xsd:documentation>
 *   </xsd:annotation>
 *   <xsd:complexType>
 *     <xsd:sequence>
 *       <xsd:element ref="sld:AnchorPoint" minOccurs="0"/>
 *       <xsd:element ref="sld:Displacement" minOccurs="0"/>
 *       <xsd:element ref="sld:Rotation" minOccurs="0"/>
 *     </xsd:sequence>
 *   </xsd:complexType>
 * </xsd:element>
 * 
 *
 * $Id$
 *
 * @author Ian Turton
 */
public interface PointPlacement extends org.opengis.style.PointPlacement, LabelPlacement {
    /**
     * Returns the AnchorPoint which identifies the location inside a textlabel to use as an
     * "anchor" for positioning it relative to a point geometry.
     *
     * @return anchorPoint from the relative to the original geometry
     */
    AnchorPoint getAnchorPoint();

    /**
     * sets the AnchorPoint which identifies the location inside a textlabel to use as an "anchor"
     * for positioning it relative to a point geometry.
     *
     * @param anchorPoint relative to the original geometry
     */
    void setAnchorPoint(org.opengis.style.AnchorPoint anchorPoint);

    /**
     * Returns the Displacement which gives X and Y offset displacements to use for rendering a text
     * label near a point.
     *
     * @return Offset to use when rendering text near a point
     */
    Displacement getDisplacement();

    /**
     * sets the Displacement which gives X and Y offset displacements to use for rendering a text
     * label near a point.
     */
    void setDisplacement(org.opengis.style.Displacement displacement);

    /**
     * Returns the rotation of the label.
     *
     * @return rotation of the label as a dynamic expression
     */
    Expression getRotation();

    /**
     * sets the rotation of the label.
     *
     * Sets the rotation of the label.
     */
    void setRotation(Expression rotation);

    static final AnchorPoint DEFAULT_ANCHOR_POINT =
            new AnchorPoint() {
                private void cannotModifyConstant() {
                    throw new UnsupportedOperationException(
                            "Constant AnchorPoint may not be modified");
                }

                @Override
                public void setAnchorPointX(Expression x) {
                    cannotModifyConstant();
                }

                @Override
                public void setAnchorPointY(Expression y) {
                    cannotModifyConstant();
                }

                @Override
                public void accept(org.geotools.styling.StyleVisitor visitor) {
                    cannotModifyConstant();
                }

                @Override
                public Object accept(org.opengis.style.StyleVisitor visitor, Object data) {
                    cannotModifyConstant();
                    return null;
                }

                @Override
                public Expression getAnchorPointX() {
                    return ConstantExpression.constant(0.0);
                }

                @Override
                public Expression getAnchorPointY() {
                    return ConstantExpression.constant(0.5);
                }
            };
}