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 }