LineBreakingReader.java :  » IDE-Eclipse » jface » org » eclipse » jface » internal » text » link » contentassist » Java Open Source

/*******************************************************************************
 * Copyright (c) 2000, 2008 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.jface.internal.text.link.contentassist;


import java.io.BufferedReader;
import java.io.IOException;
import java.io.Reader;

import com.ibm.icu.text.BreakIterator;

import org.eclipse.swt.graphics.GC;

/*
 * Not a real reader. Could change if requested
 */
public class LineBreakingReader {

  private BufferedReader fReader;
  private GC fGC;
  private int fMaxWidth;

  private String fLine;
  private int fOffset;

  private BreakIterator fLineBreakIterator;
  private boolean fBreakWords;

  /**
   * Creates a reader that breaks an input text to fit in a given width.
   *
   * @param reader Reader of the input text
   * @param gc The graphic context that defines the currently used font sizes
   * @param maxLineWidth The max width (pixels) where the text has to fit in
   */
  public LineBreakingReader(Reader reader, GC gc, int maxLineWidth) {
    fReader= new BufferedReader(reader);
    fGC= gc;
    fMaxWidth= maxLineWidth;
    fOffset= 0;
    fLine= null;
    fLineBreakIterator= BreakIterator.getLineInstance();
    fBreakWords= true;
  }

  public boolean isFormattedLine() {
    return fLine != null;
  }

  /**
   * Reads the next line. The lengths of the line will not exceed the given maximum width.
   *
   * @return the next line
   * @throws IOException if an I/O error occurs
   */
  public String readLine() throws IOException {
    if (fLine == null) {
      String line= fReader.readLine();
      if (line == null)
        return null;

      int lineLen= fGC.textExtent(line).x;
      if (lineLen < fMaxWidth) {
        return line;
      }
      fLine= line;
      fLineBreakIterator.setText(line);
      fOffset= 0;
    }
    int breakOffset= findNextBreakOffset(fOffset);
    String res;
    if (breakOffset != BreakIterator.DONE) {
      res= fLine.substring(fOffset, breakOffset);
      fOffset= findWordBegin(breakOffset);
      if (fOffset == fLine.length()) {
        fLine= null;
      }
    } else {
      res= fLine.substring(fOffset);
      fLine= null;
    }
    return res;
  }

  private int findNextBreakOffset(int currOffset) {
    int currWidth= 0;
    int nextOffset= fLineBreakIterator.following(currOffset);
    while (nextOffset != BreakIterator.DONE) {
      String word= fLine.substring(currOffset, nextOffset);
      int wordWidth= fGC.textExtent(word).x;
      int nextWidth= wordWidth + currWidth;
      if (nextWidth > fMaxWidth) {
        if (currWidth > 0)
          return currOffset;

        if (!fBreakWords)
          return nextOffset;

        // need to fit into fMaxWidth
        int length= word.length();
        while (length >= 0) {
          length--;
          word= word.substring(0, length);
          wordWidth= fGC.textExtent(word).x;
          if (wordWidth + currWidth < fMaxWidth)
            return currOffset + length;
        }
        return nextOffset;
      }
      currWidth= nextWidth;
      currOffset= nextOffset;
      nextOffset= fLineBreakIterator.next();
    }
    return nextOffset;
  }

  private int findWordBegin(int idx) {
    while (idx < fLine.length() && Character.isWhitespace(fLine.charAt(idx))) {
      idx++;
    }
    return idx;
  }
}