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Open Source (LGPL) JavaFX PDF Viewer

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/*
 * ===========================================
 * Java Pdf Extraction Decoding Access Library
 * ===========================================
 *
 * Project Info:  http://www.idrsolutions.com
 * Help section for developers at http://www.idrsolutions.com/support/
 *
 * (C) Copyright 1997-2017 IDRsolutions and Contributors.
 *
 * This file is part of JPedal/JPDF2HTML5
 *
 @LICENSE@
 *
 * ---------------
 * ViewStack.java
 * ---------------
 */
package org.jpedal.examples.viewer.commands;

import java.awt.Rectangle;
import java.util.ArrayList;

/**
 * the view stack type object that allows us to store views as they change and
 * then go back through them as needed.
 *
 * @author Chris Wade
 */
public class ViewStack {

    private final ArrayList ourStack = new ArrayList();
    private int index = -1;
    private int length;

    public Viewable back() {

        if (index - 1 > -1 && index - 1 < length) {
            index--;
            return ourStack.get(index);
        } else {
            return null;
        }
    }

    public Viewable forward() {

        if (index + 1 > -1 && index + 1 < length) {
            index++;
            return ourStack.get(index);
        } else {
            return null;
        }
    }

    public synchronized void add(final int page, final Rectangle location, final Integer scalingType) {
        //check capacity will take the new object and location +1 and +1 for the length.
        ourStack.ensureCapacity(index + 2);
        ourStack.add(index + 1, new Viewable(page, location, scalingType));

        //set the index and length after to ensure correct runing if an exception
        index++;
        length = index + 1;
    }
}