src/java/org/apache/fop/layoutmgr/KnuthGlue.java

/*
 * Copyright 2004-2005 The Apache Software Foundation.
 * 
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/* $Id$ */

package org.apache.fop.layoutmgr;

/**
 * An instance of this class represents a piece of content with adjustable 
 * width: for example a space between words of justified text.
 * 
 * A KnuthGlue is a feasible breaking point only if it immediately follows
 * a KnuthBox.
 * 
 * The represented piece of content is suppressed if either the KnuthGlue
 * is a chosen breaking point or there isn't any KnuthBox between the
 * previous breaking point and the KnuthGlue itself.
 * 
 * So, an unsuppressible piece of content with adjustable width, for example
 * a leader or a word with adjustable letter space, cannot be represented
 * by a single KnuthGlue; it can be represented using the sequence:
 *   KnuthBox(width = 0)
 *   KnuthPenalty(width = 0, penalty = infinity)
 *   KnuthGlue(...)
 *   KnuthBox(width = 0)
 * where the infinity penalty avoids choosing the KnuthGlue as a breaking point
 * and the 0-width KnuthBoxes prevent suppression.
 * 
 * Besides the inherited methods and attributes, this class has two attributes
 * used to store the stretchability (difference between max and opt width) and
 * the shrinkability (difference between opt and min width), and the methods
 * to get these values.
 */
public class KnuthGlue extends KnuthElement {
    
    private int stretchability;
    private int shrinkability;
    private int adjustmentClass = -1;

    /**
     * Create a new KnuthGlue.
     *
     * @param w the width of this glue
     * @param y the stretchability of this glue
     * @param z the shrinkability of this glue
     * @param pos the Position stored in this glue
     * @param bAux is this glue auxiliary?
     */
    public KnuthGlue(int w, int y, int z, Position pos, boolean bAux) {
        super(w, pos, bAux);
        stretchability = y;
        shrinkability = z;
    }

    public KnuthGlue(int w, int y, int z,
            int iAdjClass, Position pos, boolean bAux) {
        super(w, pos, bAux);
        stretchability = y;
        shrinkability = z;
        adjustmentClass = iAdjClass;
    }

    /** @see org.apache.fop.layoutmgr.KnuthElement#isGlue() */
    public boolean isGlue() {
        return true;
    }

    /** @return the stretchability of this glue. */
    public int getY() {
        return stretchability;
    }

    /** @return the shrinkability of this glue. */
    public int getZ() {
        return shrinkability;
    }
    
    /** @return the adjustment class (or role) of this glue. */
    public int getAdjustmentClass() {
        return adjustmentClass;
    }
    
    /** @see java.lang.Object#toString() */
    public String toString() {
        StringBuffer sb = new StringBuffer(64);
        if (isAuxiliary()) {
            sb.append("aux. ");
        }
        sb.append("glue");
        sb.append(" w=").append(getW());
        sb.append(" stretch=").append(getY());
        sb.append(" shrink=").append(getZ());
        if (getAdjustmentClass() >= 0) {
            sb.append(" adj-class=").append(getAdjustmentClass());
        }
        return sb.toString();
    }
    
}