core/org.eclipse.ptp.ui/src/org/eclipse/ptp/internal/ui/hover/LineBreakingReader.java

/*******************************************************************************
 * Copyright (c) 2005 The Regents of the University of California. 
 * This material was produced under U.S. Government contract W-7405-ENG-36 
 * for Los Alamos National Laboratory, which is operated by the University 
 * of California for the U.S. Department of Energy. The U.S. Government has 
 * rights to use, reproduce, and distribute this software. NEITHER THE 
 * GOVERNMENT NOR THE UNIVERSITY MAKES ANY WARRANTY, EXPRESS OR IMPLIED, OR 
 * ASSUMES ANY LIABILITY FOR THE USE OF THIS SOFTWARE. If software is modified 
 * to produce derivative works, such modified software should be clearly marked, 
 * so as not to confuse it with the version available from LANL.
 * 
 * Additionally, 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
 * 
 * LA-CC 04-115
 *******************************************************************************/
package org.eclipse.ptp.internal.ui.hover;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.Reader;
import java.text.BreakIterator;
import org.eclipse.swt.graphics.GC;
/**
 * @author Clement chu
 */
public class LineBreakingReader {
	private BufferedReader fReader;
	private GC fGC;
	private int fMaxWidth;
	private String fLine;
	private int fOffset;
	private int fLineLen;
	private BreakIterator fLineBreakIterator;
	/**
	 * 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 (pixes) 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();
	}
	/**
	 * Is formatted line
	 * 
	 * @return true if it is a formatted line
	 */
	public boolean isFormattedLine() {
		return fLine != null;
	}
	/**
	 * Reads the next line. The lengths of the line will not exceed the gived maximum width
	 * 
	 * @param indent
	 * @return
	 * @throws IOException
	 */
	public String readLine(String indent) throws IOException {
		if (fLine == null) {
			String line = fReader.readLine();
			if (line == null)
				return null;
			int lineLen = fGC.textExtent(line).x;
			if (fMaxWidth > -1 && lineLen < fMaxWidth) {
				return line;
			}
			fLine = line;
			fLineBreakIterator.setText(line);
			fOffset = 0;
		}
		int breakOffset = findNextBreakOffset(fOffset, indent);
		String res;
		if (breakOffset != BreakIterator.DONE) {
			res = fLine.substring(fOffset, breakOffset);
			fOffset = findWordBegin(breakOffset);
			if (fOffset == fLine.length()) {
				fLine = null;
			}
			if (breakOffset == 1 && res.charAt(0) == '\t') {// added to prevent empty line
				return "\t" + readLine(indent);
			}
		} else {
			res = fLine.substring(fOffset);
			fLine = null;
		}
		return res;
	}
	public String readLine() throws IOException {
		if (fLine == null) {
			String line = fReader.readLine();
			if (line == null)
				return null;
			fLineLen = line.length();
			if (fMaxWidth == -1 || fLineLen < fMaxWidth) {
				return line;
			}
			fLine = line;
			fOffset = 0;
		}
		int endLen = fOffset + fMaxWidth;
		if (endLen > fLineLen)
			endLen = fLineLen;
		String res = fLine.substring(fOffset, endLen);
		fOffset = endLen;
		if (fOffset >= fLineLen) {
			fLine = null;
			fLineLen = 0;
		}
		if (res.charAt(0) == '\t') {// added to prevent empty line
			return "\t" + res;
		}
		return res;
	}
	/**
	 * Find next breaj offset
	 * 
	 * @param currOffset
	 * @param indent
	 * @return
	 */
	private int findNextBreakOffset(int currOffset, String indent) {
		int currWidth = indent != null ? fGC.textExtent(indent).x : 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 (fMaxWidth > -1 && nextWidth > fMaxWidth) {
				if (currWidth > 0) {
					return currOffset;
				} else {
					return nextOffset;
				}
			}
			currWidth = nextWidth;
			currOffset = nextOffset;
			nextOffset = fLineBreakIterator.next();
		}
		return nextOffset;
	}
	/**
	 * Find word begin index
	 * 
	 * @param idx
	 * @return
	 */
	private int findWordBegin(int idx) {
		while (idx < fLine.length() && Character.isWhitespace(fLine.charAt(idx))) {
			idx++;
		}
		return idx;
	}
}