001 /* TextMeasurer.java
002 Copyright (C) 2006 Free Software Foundation, Inc.
003
004 This file is part of GNU Classpath.
005
006 GNU Classpath is free software; you can redistribute it and/or modify
007 it under the terms of the GNU General Public License as published by
008 the Free Software Foundation; either version 2, or (at your option)
009 any later version.
010
011 GNU Classpath is distributed in the hope that it will be useful, but
012 WITHOUT ANY WARRANTY; without even the implied warranty of
013 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
014 General Public License for more details.
015
016 You should have received a copy of the GNU General Public License
017 along with GNU Classpath; see the file COPYING. If not, write to the
018 Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
019 02110-1301 USA.
020
021 Linking this library statically or dynamically with other modules is
022 making a combined work based on this library. Thus, the terms and
023 conditions of the GNU General Public License cover the whole
024 combination.
025
026 As a special exception, the copyright holders of this library give you
027 permission to link this library with independent modules to produce an
028 executable, regardless of the license terms of these independent
029 modules, and to copy and distribute the resulting executable under
030 terms of your choice, provided that you also meet, for each linked
031 independent module, the terms and conditions of the license of that
032 module. An independent module is a module which is not derived from
033 or based on this library. If you modify this library, you may extend
034 this exception to your version of the library, but you are not
035 obligated to do so. If you do not wish to do so, delete this
036 exception statement from your version. */
037
038
039 package java.awt.font;
040
041 import java.text.AttributedCharacterIterator;
042 import 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 */
051 public 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 }