001/* TextMeasurer.java
002   Copyright (C) 2006 Free Software Foundation, Inc.
003
004This file is part of GNU Classpath.
005
006GNU Classpath is free software; you can redistribute it and/or modify
007it under the terms of the GNU General Public License as published by
008the Free Software Foundation; either version 2, or (at your option)
009any later version.
010
011GNU Classpath is distributed in the hope that it will be useful, but
012WITHOUT ANY WARRANTY; without even the implied warranty of
013MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
014General Public License for more details.
015
016You should have received a copy of the GNU General Public License
017along with GNU Classpath; see the file COPYING.  If not, write to the
018Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
01902110-1301 USA.
020
021Linking this library statically or dynamically with other modules is
022making a combined work based on this library.  Thus, the terms and
023conditions of the GNU General Public License cover the whole
024combination.
025
026As a special exception, the copyright holders of this library give you
027permission to link this library with independent modules to produce an
028executable, regardless of the license terms of these independent
029modules, and to copy and distribute the resulting executable under
030terms of your choice, provided that you also meet, for each linked
031independent module, the terms and conditions of the license of that
032module.  An independent module is a module which is not derived from
033or based on this library.  If you modify this library, you may extend
034this exception to your version of the library, but you are not
035obligated to do so.  If you do not wish to do so, delete this
036exception statement from your version. */
037
038
039package java.awt.font;
040
041import java.text.AttributedCharacterIterator;
042import java.awt.Shape;
043
044/**
045 * TextMeasurer is a small utility class for measuring the length of laid-out
046 * text objects. 
047 *
048 * @author Sven de Marothy
049 * @since 1.3
050 */
051public final class TextMeasurer implements Cloneable
052{
053  private AttributedCharacterIterator text;
054  private FontRenderContext frc;
055  private TextLayout totalLayout;
056  private int numChars;
057
058  /**
059   * Creates a TextMeasurer from a given text in the form of an
060   * <code>AttributedCharacterIterator</code> and a 
061   * <code>FontRenderContext</code>.
062   */  
063  public TextMeasurer (AttributedCharacterIterator text, FontRenderContext frc)
064  {
065    this.text = text;
066    this.frc = frc;
067    totalLayout = new TextLayout( text, frc );
068    numChars = totalLayout.getCharacterCount();
069  }
070
071  /**
072   * Clones the TextMeasurer object
073   */
074  protected Object clone ()
075  {
076    return new TextMeasurer( text, frc );
077  }
078
079  /**
080   * Update the text if a character is deleted at the position deletePos
081   * @param newParagraph - the updated paragraph.
082   * @param deletePos - the deletion position
083   */
084  public void deleteChar (AttributedCharacterIterator newParagraph,
085                          int deletePos)
086  {
087    totalLayout = new TextLayout(newParagraph, frc);
088    if( deletePos < 0 || deletePos > totalLayout.getCharacterCount() )
089      throw new NullPointerException("Invalid deletePos:"+deletePos);
090    numChars = totalLayout.getCharacterCount();
091    text = newParagraph;
092  }
093
094  /**
095   * Update the text if a character is inserted at the position insertPos
096   * @param newParagraph - the updated paragraph.
097   * @param insertPos - the insertion position
098   */
099  public void insertChar (AttributedCharacterIterator newParagraph,
100                          int insertPos)
101  {
102    totalLayout = new TextLayout(newParagraph, frc);
103    if( insertPos < 0 || insertPos > totalLayout.getCharacterCount() )
104      throw new NullPointerException("Invalid insertPos:"+insertPos);
105    numChars = totalLayout.getCharacterCount();
106    text = newParagraph;
107  }
108
109  /***
110   * Returns the total advance between two positions in the paragraph.
111   * Characters from start to limit-1 (inclusive) are included in this count.
112   *
113   * @param start - the starting character index.
114   * @param limit - the limiting index.
115   */
116  public float getAdvanceBetween (int start, int limit)
117  {
118    Shape s = totalLayout.getLogicalHighlightShape( start, limit );
119    return (float)s.getBounds2D().getWidth();
120  }
121
122  /**
123   * Returns a <code>TextLayout</code> object corresponding to the characters
124   * from text to limit.
125   * @param start - the starting character index.
126   * @param limit - the limiting index.
127   */
128  public TextLayout getLayout (int start, int limit)
129  {
130    if( start >= limit )
131      throw new IllegalArgumentException("Start position must be < limit.");
132    return new TextLayout( totalLayout, start, limit );
133  }
134
135  /**
136   * Returns the line-break index from a given starting index and a maximum
137   * advance. The index returned is the first character outside the given
138   * advance (or the limit of the string, if all remaining characters fit.)
139   *
140   * @param start - the starting index.
141   * @param maxAdvance - the maximum advance allowed.
142   * @return the index of the first character beyond maxAdvance, or the 
143   * index of the last character + 1.
144   */
145  public int getLineBreakIndex (int start, float maxAdvance)
146  {   
147    if( start < 0 )
148      throw new IllegalArgumentException("Start parameter must be > 0.");
149
150    double remainingLength = getAdvanceBetween( start, numChars );
151    
152    int guessOffset = (int)( ( (double)maxAdvance / (double)remainingLength)
153                             * ( (double)numChars - (double)start ) );
154    guessOffset += start;
155    if( guessOffset > numChars )
156      guessOffset = numChars;
157    
158    double guessLength = getAdvanceBetween( start, guessOffset );
159    boolean makeSmaller = ( guessLength > maxAdvance );
160    int inc = makeSmaller ? -1 : 1;
161    boolean keepGoing = true;
162
163    do
164      {
165        guessOffset = guessOffset + inc;
166        if( guessOffset <= start || guessOffset > numChars )
167          {
168            keepGoing = false;
169          }
170        else
171          {
172            guessLength = getAdvanceBetween( start, guessOffset );
173            if( makeSmaller && ( guessLength <= maxAdvance) )          
174              keepGoing = false;
175            if( !makeSmaller && ( guessLength >= maxAdvance) )
176              keepGoing = false;
177          }
178      }
179    while( keepGoing );
180
181    // Return first index that doesn't fit.
182    if( !makeSmaller )
183      guessOffset--;
184
185    if( guessOffset > numChars )
186      return numChars;
187
188    return guessOffset;
189  }
190}