RelativeLength.java

/*******************************************************************************
 * Copyright (c) 2004, 2008 John Krasnay and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 * 
 * Contributors:
 *     John Krasnay - initial API and implementation
 *******************************************************************************/
package net.sf.vex.css;

import java.io.Serializable;

/**
 * A length that may be expressed as an absolute or relative value.
 */
public class RelativeLength implements Serializable {
    
    private static final long serialVersionUID = 1L;

    private float percentage;
    private int absolute;
    boolean isAbsolute;
    
    private static RelativeLength ZERO = new RelativeLength(0, 0, true);
    
    /**
     * Create a relative length representing an absolute value.
     * @return the new RelativeLength value.
     */
    public static RelativeLength createAbsolute(int value) {
        if (value == 0) {
            return ZERO;
        } else {
            return new RelativeLength(0, value, true);
        }
    }

    /**
     * Create a relative length representing a relative value.
     * @return the new RelativeLength value.
     */
    public static RelativeLength createRelative(float percentage) {
        return new RelativeLength(percentage, 0, false);
    }

    /**
     * Return the value of the length given a reference value. If this
     * object represents an absolute value, that value is simply returned.
     * Otherwise, returns the given reference length multiplied by the given
     * percentage and rounded to the nearest integer.
     * @param referenceLength reference length by which percentage lengths
     * will by multiplied.
     * @return the actual value
     */
    public int get(int referenceLength) {
        if (this.isAbsolute) {
            return this.absolute;
        } else {
            return Math.round(this.percentage * referenceLength);
        }
    }
    
    //==================================================== PRIVATE
    
    private RelativeLength(float percentage, int absolute, boolean isAbsolute) {
        this.percentage = percentage;
        this.absolute = absolute;
        this.isAbsolute = isAbsolute;
    }
}