bundles/org.eclipse.wst.sse.ui/src/org/eclipse/wst/sse/ui/internal/StructuredTextLineBreakingReader.java

/*******************************************************************************
 * Copyright (c) 2001, 2005 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
 *     Jens Lukowski/Innoopract - initial renaming/restructuring
 *     
 *******************************************************************************/
package org.eclipse.wst.sse.ui.internal;



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

import org.eclipse.swt.graphics.GC;

/*
 * Not a real reader. Could change if requested
 */
public class StructuredTextLineBreakingReader {
	private GC fGC;
	private int fIndex;
	private String fLine;
	private int fMaxWidth;

	private BufferedReader fReader;

	/**
	 * 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 StructuredTextLineBreakingReader(Reader reader, GC gc, int maxLineWidth) {
		fReader = new BufferedReader(reader);
		fGC = gc;
		fMaxWidth = maxLineWidth;
		fLine = null;
		fIndex = 0;
	}

	private int findNextBreakIndex(int currIndex) {
		int currWidth = 0;
		int lineLength = fLine.length();

		while (currIndex < lineLength) {
			char ch = fLine.charAt(currIndex);
			int nextIndex = currIndex + 1;
			// leading whitespaces are counted to the following word
			if (Character.isWhitespace(ch)) {
				while (nextIndex < lineLength && Character.isWhitespace(fLine.charAt(nextIndex))) {
					nextIndex++;
				}
			}
			while (nextIndex < lineLength && !Character.isWhitespace(fLine.charAt(nextIndex))) {
				nextIndex++;
			}
			String word = fLine.substring(currIndex, nextIndex);
			int wordWidth = fGC.textExtent(word).x;
			int nextWidth = wordWidth + currWidth;
			if (nextWidth > fMaxWidth && wordWidth < fMaxWidth) {
				return currIndex;
			}
			currWidth = nextWidth;
			currIndex = nextIndex;
		}
		return currIndex;
	}

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

	/**
	 * Reads the next line. The lengths of the line will not exceed the gived
	 * maximum width.
	 */
	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;
			fIndex = 0;
		}
		int breakIdx = findNextBreakIndex(fIndex);
		String res = fLine.substring(fIndex, breakIdx);
		if (breakIdx < fLine.length()) {
			fIndex = findWordBegin(breakIdx);
		} else {
			fLine = null;
		}
		return res;
	}
}