Source for java.awt.font.TextMeasurer

   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:    */
  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:    */
  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:    */
  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:    */
  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:    */
 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: }