http://xmlgraphics.apache.org/batik/batik-gvt/: Batik Graphics Vector Tree (GVT) (Apache Software Foundation) 
/*

   Licensed to the Apache Software Foundation (ASF) under one or more
   contributor license agreements.  See the NOTICE file distributed with
   this work for additional information regarding copyright ownership.
   The ASF licenses this file to You 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.

 */
package org.apache.batik.gvt.text;

import java.text.AttributedCharacterIterator;
import java.text.AttributedString;
import java.text.CharacterIterator;
import java.text.StringCharacterIterator;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;


GVTACIImpl
Used to implement SVG <tspan> and <text>
attributes.  This implementation is designed for efficient support
of per-character attributes (i.e. single character attribute spans).
It supports an extended set of TextAttributes, via inner class
GVTAttributedCharacterIterator.TextAttributes.

Author:Bill Haneman
Version:$Id: GVTACIImpl.java 1831635 2018-05-15 13:33:47Z ssteiner $
/**
 * GVTACIImpl
 *
 * Used to implement SVG &lt;tspan&gt; and &lt;text&gt;
 * attributes.  This implementation is designed for efficient support
 * of per-character attributes (i.e. single character attribute spans).
 * It supports an extended set of TextAttributes, via inner class
 * GVTAttributedCharacterIterator.TextAttributes.
 *
 * @author <a href="mailto:bill.haneman@ireland.sun.com">Bill Haneman</a>
 * @version $Id: GVTACIImpl.java 1831635 2018-05-15 13:33:47Z ssteiner $
 */

public class GVTACIImpl
                implements GVTAttributedCharacterIterator {

    private String simpleString;
    private Set allAttributes;
    private ArrayList mapList;
    private static int START_RUN = 2;
    private static int END_RUN = 3;
    private static int MID_RUN = 1;
    private static int SINGLETON = 0;
    private int[] charInRun;
    private CharacterIterator iter = null;
    private int currentIndex = -1;

    
Constructs a new GVTAttributedCharacterIterator with no attributes
    and a null string.

/**
     * Constructs a new GVTAttributedCharacterIterator with no attributes
     *     and a null string.
     */
    public GVTACIImpl() {
        simpleString = "";
        buildAttributeTables();
    }

    
Constructs a GVTACIImpl whose contents are
    equivalent to those of aci.
This constructor creates a new copy of the source data in aci.

/**
     * Constructs a GVTACIImpl whose contents are
     *     equivalent to those of aci.
     * This constructor creates a new copy of the source data in <code>aci</code>.
     */
    public GVTACIImpl(AttributedCharacterIterator aci) {
        buildAttributeTables(aci);
    }

    
Sets this iterator's contents to an unattributed copy of String s.

/**
     * Sets this iterator's contents to an unattributed copy of String s.
     */
    public void setString(String s) {
        simpleString = s;
        iter = new StringCharacterIterator(simpleString);
        buildAttributeTables();
    }

    
Assigns this iterator's contents to be equivalent to AttributedString s.

/**
     * Assigns this iterator's contents to be equivalent to AttributedString s.
     */
    public void setString(AttributedString s) {
        iter = s.getIterator();
        buildAttributeTables((AttributedCharacterIterator) iter);
    }

    
Sets values of a per-character attribute associated with the
    content string.
Characters from beginIndex to endIndex
    (zero-offset) are assigned values for attribute key attr
    from the array attValues.
If the length of attValues is less than character span
    (endIndex-beginIndex) the last value is duplicated;
    if attValues is longer than the character span
    the extra values are ignored.
Note that if either beginIndex or endIndex are outside the bounds
    of the current character array they are clipped accordingly.

/**
     * Sets values of a per-character attribute associated with the
     *     content string.
     * Characters from <code>beginIndex</code> to <code>endIndex</code>
     *     (zero-offset) are assigned values for attribute key <code>attr</code>
     *     from the array <code>attValues.</code>
     * If the length of attValues is less than character span
     *     <code>(endIndex-beginIndex)</code> the last value is duplicated;
     *     if attValues is longer than the character span
     *     the extra values are ignored.
     * Note that if either beginIndex or endIndex are outside the bounds
     *     of the current character array they are clipped accordingly.
     */
    public void setAttributeArray
        (GVTAttributedCharacterIterator.TextAttribute attr,
         Object[] attValues, int beginIndex, int endIndex) {

        beginIndex = Math.max(beginIndex, 0);
        endIndex = Math.min(endIndex, simpleString.length());
        if (charInRun[beginIndex] == END_RUN) {
            if (charInRun[beginIndex - 1] == MID_RUN) {
                charInRun[beginIndex - 1] = END_RUN;
            } else {
                charInRun[beginIndex - 1] = SINGLETON;
            }
        }
        if (charInRun[endIndex + 1] == END_RUN) {
            charInRun[endIndex + 1] = SINGLETON;
        } else if (charInRun[endIndex + 1] == MID_RUN) {
            charInRun[endIndex + 1] = START_RUN;
        }
        for (int i = beginIndex; i <= endIndex; ++i) {
            charInRun[i] = SINGLETON;
            int n = Math.min(i, attValues.length - 1);
            ((Map) mapList.get(i)).put(attr, attValues[n]);
        }
    }

    //From java.text.AttributedCharacterIterator

    
Get the keys of all attributes defined on the iterator's text range.

/**
     * Get the keys of all attributes defined on the iterator's text range.
     */
    public Set getAllAttributeKeys() {
        return allAttributes;
    }

    
Get the value of the named attribute for the current
    character.

/**
     * Get the value of the named attribute for the current
     *     character.
     */
    public Object getAttribute(AttributedCharacterIterator.Attribute attribute)
    {
        return getAttributes().get(attribute);
    }

    
Returns a map with the attributes defined on the current
character.

/**
     * Returns a map with the attributes defined on the current
     * character.
     */
    public Map getAttributes() {
        return (Map) mapList.get(currentIndex);
    }

    
Get the index of the first character following the
    run with respect to all attributes containing the current
    character.

/**
     * Get the index of the first character following the
     *     run with respect to all attributes containing the current
     *     character.
     */
    public int getRunLimit() {
        int  ndx = currentIndex;
        do {
            ++ndx;
        } while (charInRun[ndx] == MID_RUN);
        return ndx;
    }

    
Get the index of the first character following the
     run with respect to the given attribute containing the current
     character.

/**
     * Get the index of the first character following the
     *      run with respect to the given attribute containing the current
     *      character.
     */
    public int getRunLimit(AttributedCharacterIterator.Attribute attribute) {
        int ndx = currentIndex;
        Object  value = getAttributes().get(attribute);

        //to avoid null pointer, treat null value as special case:-(
        if (value == null) {
            do {
                 ++ndx;
            } while (((Map) mapList.get(ndx)).get(attribute) == null);
        } else {
            do {
                ++ndx;
            } while (value.equals(((Map) mapList.get(ndx)).get(attribute)));
        }
        return ndx;
    }


    
Get the index of the first character following the
    run with respect to the given attributes containing the current
    character.

/**
     * Get the index of the first character following the
     *     run with respect to the given attributes containing the current
     *     character.
     */
    public int getRunLimit(Set attributes) {
        int ndx = currentIndex;
        do {
            ++ndx;
        } while (attributes.equals(mapList.get(ndx)));
        return ndx;
    }

    
Get the index of the first character of the run with
   respect to all attributes containing the current character.

/**
     * Get the index of the first character of the run with
     *    respect to all attributes containing the current character.
     */
    public int getRunStart() {
        int ndx = currentIndex;
        while (charInRun[ndx] == MID_RUN) --ndx;
        return ndx;
    }

    
Get the index of the first character of the run with
     respect to the given attribute containing the current character.

Params:
  • attribute – The attribute for whose appearance the first offset
     is requested.
/**
     * Get the index of the first character of the run with
     *      respect to the given attribute containing the current character.
     * @param attribute The attribute for whose appearance the first offset
     *      is requested.
     */
    public int getRunStart(AttributedCharacterIterator.Attribute attribute) {
        int ndx = currentIndex - 1;
        Object value = getAttributes().get(attribute);

        //to avoid null pointer, treat null value as special case:-(
        try {
            if (value == null) {
                while (((Map) mapList.get(ndx - 1)).get(attribute) == null)
                    --ndx;
            } else {
                while (value.equals(
                        ((Map) mapList.get(ndx - 1)).get(attribute)) )
                    --ndx;
            }
        } catch(IndexOutOfBoundsException e) {
        }
        return ndx;
    }

    
Get the index of the first character of the run with
     respect to the given attributes containing the current character.

Params:
  • attributes – the Set of attributes which begins at the returned
     index.
/**
     * Get the index of the first character of the run with
     *      respect to the given attributes containing the current character.
     * @param attributes the Set of attributes which begins at the returned
     *      index.
     */
    public int getRunStart(Set attributes) {
        int ndx = currentIndex;
        try {
            while (attributes.equals(mapList.get(ndx - 1))) --ndx;
        } catch(IndexOutOfBoundsException e) {
        }
        return ndx;
    }

    //From CharacterIterator

    
Create a copy of this iterator

/**
     * Create a copy of this iterator
     */
    public Object clone() {
        GVTAttributedCharacterIterator cloneACI =
                new GVTACIImpl(this);
        return cloneACI;
    }

    
Get the character at the current position (as returned
     by getIndex()).

Specified by: java.text.CharacterIterator.

/**
     * Get the character at the current position (as returned
     *      by getIndex()).
     * <br><b>Specified by:</b> java.text.CharacterIterator.
     */
    public char current() {
        return iter.current();
    }

    
Sets the position to getBeginIndex().

Returns:the character at the start index of the text.

Specified by: java.text.CharacterIterator.
/**
     * Sets the position to getBeginIndex().
     * @return the character at the start index of the text.
     * <br><b>Specified by:</b> java.text.CharacterIterator.
     */
    public char first() {
        return iter.first();
    }

    
Get the start index of the text.

Specified by: java.text.CharacterIterator.

/**
     * Get the start index of the text.
     * <br><b>Specified by:</b> java.text.CharacterIterator.
     */
    public int getBeginIndex() {
        return iter.getBeginIndex();
    }

    
Get the end index of the text.

Specified by: java.text.CharacterIterator.

/**
     * Get the end index of the text.
     * <br><b>Specified by:</b> java.text.CharacterIterator.
     */
    public int getEndIndex() {
        return iter.getEndIndex();
    }

    
Get the current index.

Specified by: java.text.CharacterIterator.

/**
     * Get the current index.
     * <br><b>Specified by:</b> java.text.CharacterIterator.
     */
    public int getIndex() {
        return iter.getIndex();
    }

    
Sets the position to getEndIndex()-1 (getEndIndex() if
the text is empty) and returns the character at that position.

Specified by: java.text.CharacterIterator.

/**
     * Sets the position to getEndIndex()-1 (getEndIndex() if
     * the text is empty) and returns the character at that position.
     * <br><b>Specified by:</b> java.text.CharacterIterator.
     */
    public char last() {
        return iter.last();
    }

    
Increments the iterator's index by one, returning the next character.

Returns:the character at the new index.

Specified by: java.text.CharacterIterator.
/**
     * Increments the iterator's index by one, returning the next character.
     * @return the character at the new index.
     * <br><b>Specified by:</b> java.text.CharacterIterator.
     */
    public char next() {
        return iter.next();
    }

    
Decrements the iterator's index by one and returns
the character at the new index.

Specified by: java.text.CharacterIterator.

/**
     * Decrements the iterator's index by one and returns
     * the character at the new index.
     * <br><b>Specified by:</b> java.text.CharacterIterator.
     */
    public char previous() {
        return iter.previous();
    }

    
Sets the position to the specified position in the text.

Params:
  • position – The new (current) index into the text.
Returns:the character at new index position.

Specified by: java.text.CharacterIterator.
/**
     * Sets the position to the specified position in the text.
     * @param position The new (current) index into the text.
     * @return the character at new index <em>position</em>.
     * <br><b>Specified by:</b> java.text.CharacterIterator.
     */
    public char setIndex(int position) {
        return iter.setIndex(position);
    }

    //Private methods:

    private void buildAttributeTables() {
        allAttributes = new HashSet();
        mapList = new ArrayList(simpleString.length());
        charInRun = new int[simpleString.length()];
        for (int i = 0; i < charInRun.length; ++i) {
            charInRun[i] = SINGLETON;
            /*
             * XXX TODO: loosen assumption, initially each character has its own
             * attribute map.
             */
            mapList.set(i, new HashMap());
        }
    }

    private void buildAttributeTables(AttributedCharacterIterator aci) {
        allAttributes = aci.getAllAttributeKeys();
        int length = aci.getEndIndex() - aci.getBeginIndex();
        mapList = new ArrayList(length);
        charInRun = new int[length];
        char  c = aci.first();
        char[] chars = new char[length];
        for (int i = 0; i < length; ++i) {
            chars[i] = c;
            charInRun[i] = SINGLETON;
            /*
             * XXX TODO:loosen assumption, initially each character
             * has its own attribute map.
             */
            mapList.set(i, new HashMap(aci.getAttributes()));
            c = aci.next();
        }
        simpleString = new String(chars);
    }

    //Inner classes:

    
AttributeFilter which converts (extended) location attributes
SVGAttributedCharacterIterator.TextAttribute.X, TextAttribute.Y,
TextAttribute.ROTATE attributes to TextAttribute.TRANSFORM attributes.

/**
     * AttributeFilter which converts (extended) location attributes
     * SVGAttributedCharacterIterator.TextAttribute.X, TextAttribute.Y,
     * TextAttribute.ROTATE attributes to TextAttribute.TRANSFORM attributes.
     */
    public static class TransformAttributeFilter implements
                     GVTAttributedCharacterIterator.AttributeFilter {

        
Return a new AttributedCharacterIterator instance
in which location attributes have been converted to
TextAttribute.TRANSFORM attributes.

/**
         * Return a new AttributedCharacterIterator instance
         * in which location attributes have been converted to
         * TextAttribute.TRANSFORM attributes.
         */
        public AttributedCharacterIterator
                     mutateAttributes(AttributedCharacterIterator aci) {
            //TODO:Implement this !!!
            return aci;
        }
    }
}