1 /* TextMeasurer.java 2 Copyright (C) 2006 Free Software Foundation, Inc. 3 4 This file is part of GNU Classpath. 5 6 GNU Classpath is free software; you can redistribute it and/or modify 7 it under the terms of the GNU General Public License as published by 8 the Free Software Foundation; either version 2, or (at your option) 9 any later version. 10 11 GNU Classpath is distributed in the hope that it will be useful, but 12 WITHOUT ANY WARRANTY; without even the implied warranty of 13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 14 General Public License for more details. 15 16 You should have received a copy of the GNU General Public License 17 along with GNU Classpath; see the file COPYING. If not, write to the 18 Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 19 02110-1301 USA. 20 21 Linking this library statically or dynamically with other modules is 22 making a combined work based on this library. Thus, the terms and 23 conditions of the GNU General Public License cover the whole 24 combination. 25 26 As a special exception, the copyright holders of this library give you 27 permission to link this library with independent modules to produce an 28 executable, regardless of the license terms of these independent 29 modules, and to copy and distribute the resulting executable under 30 terms of your choice, provided that you also meet, for each linked 31 independent module, the terms and conditions of the license of that 32 module. An independent module is a module which is not derived from 33 or based on this library. If you modify this library, you may extend 34 this exception to your version of the library, but you are not 35 obligated to do so. If you do not wish to do so, delete this 36 exception statement from your version. */ 37 38 39 package java.awt.font; 40 41 import java.text.AttributedCharacterIterator; 42 import java.awt.Shape; 43 44 /** 45 * TextMeasurer is a small utility class for measuring the length of laid-out 46 * text objects. 47 * 48 * @author Sven de Marothy 49 * @since 1.3 50 */ 51 public final class TextMeasurer implements Cloneable 52 { 53 private AttributedCharacterIterator text; 54 private FontRenderContext frc; 55 private TextLayout totalLayout; 56 private int numChars; 57 58 /** 59 * Creates a TextMeasurer from a given text in the form of an 60 * <code>AttributedCharacterIterator</code> and a 61 * <code>FontRenderContext</code>. 62 */ TextMeasurer(AttributedCharacterIterator text, FontRenderContext frc)63 public TextMeasurer (AttributedCharacterIterator text, FontRenderContext frc) 64 { 65 this.text = text; 66 this.frc = frc; 67 totalLayout = new TextLayout( text, frc ); 68 numChars = totalLayout.getCharacterCount(); 69 } 70 71 /** 72 * Clones the TextMeasurer object 73 */ clone()74 protected Object clone () 75 { 76 return new TextMeasurer( text, frc ); 77 } 78 79 /** 80 * Update the text if a character is deleted at the position deletePos 81 * @param newParagraph - the updated paragraph. 82 * @param deletePos - the deletion position 83 */ deleteChar(AttributedCharacterIterator newParagraph, int deletePos)84 public void deleteChar (AttributedCharacterIterator newParagraph, 85 int deletePos) 86 { 87 totalLayout = new TextLayout(newParagraph, frc); 88 if( deletePos < 0 || deletePos > totalLayout.getCharacterCount() ) 89 throw new NullPointerException("Invalid deletePos:"+deletePos); 90 numChars = totalLayout.getCharacterCount(); 91 text = newParagraph; 92 } 93 94 /** 95 * Update the text if a character is inserted at the position insertPos 96 * @param newParagraph - the updated paragraph. 97 * @param insertPos - the insertion position 98 */ insertChar(AttributedCharacterIterator newParagraph, int insertPos)99 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 */ getAdvanceBetween(int start, int limit)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 */ getLayout(int start, int limit)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 */ getLineBreakIndex(int start, float maxAdvance)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 } 191