EDIT

/*******************************************************************************

 * Copyright (c) 2004, 2010 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.draw2d.text;

//import com.ibm.icu.text.Bidi;

import java.util.ArrayList;

import java.util.List;

import org.eclipse.draw2d.rap.swt.SWT;

import org.eclipse.swt.graphics.TextLayout;

/**

 * A helper class for a BlockFlow that does Bidi evaluation of all the text in

 * that block.

 * <p>

 * WARNING: This class is for INTERNAL use only.

 * 

 * @author Pratik Shah

 * @since 3.1

 */

public final class BidiProcessor {

    /*

	 * Workaround for Mac OS. AWT DLL cannot start properly on carbon.

	 * Waiting for bug 82104

	 */

	private static final boolean isMacOS = SWT.getPlatform().equals("carbon") || SWT.getPlatform().equals("cocoa"); //$NON-NLS-1$ //$NON-NLS-2$

	/**

	 * A helper class to hold information about contributions made to this

	 * processor.

	 * 

	 * @author Pratik Shah

	 * @since 3.1

	 */

	private static class BidiEntry {

		int begin, end;

		FlowFigure fig;

		BidiEntry(FlowFigure fig, int offset, int length) {

			this.fig = fig;

			this.begin = offset;

			this.end = offset + length;

		}

	}

	/**

	 * A singleton instance.

	 */

	public static final BidiProcessor INSTANCE = new BidiProcessor();

	private StringBuffer bidiText;

	private List list = new ArrayList();

	private int orientation = SWT.LEFT_TO_RIGHT;

	private BidiProcessor() {

	}

	/**

	 * Records a String contribution for this bidi context. Contributions are

	 * concatenated (in the order that they were contributed) to make the final

	 * String which will determine the bidi info for all contributors.

	 * 

	 * @param fig

	 *            the figure that is contributing the given text

	 * @param str

	 *            the text contributed by the given figure

	 * @see #addControlChar(char)

	 */

	public void add(FlowFigure fig, String str) {

		// We are currently tracking empty contributions ("")

		list.add(new BidiEntry(fig, bidiText.length(), str.length()));

		bidiText.append(str);

	}

	/**

	 * Records a character contribution for this bidi context. Contributions are

	 * concatenated (in the order that they were contributed) to make the final

	 * String which will determine the bidi info for all contributors.

	 * 

	 * @param fig

	 *            the figure that is contributing the given text

	 * @param c

	 *            the character being added

	 * @see #addControlChar(char)

	 */

	public void add(FlowFigure fig, char c) {

		list.add(new BidiEntry(fig, bidiText.length(), 1));

		bidiText.append(c);

	}

	/**

	 * This methods allows FlowFigures to contribute text that may effect the

	 * bidi evaluation, but is not text that is visible on the screen. The bidi

	 * level of such text is reported back to the contributing figure.

	 * 

	 * @param c

	 *            the control character

	 */

	public void addControlChar(char c) {

		bidiText.append(c);

	}

	/**

	 * Breaks the given int array into bidi levels for each figure based on

	 * their contributed text, and assigns those levels to each figure. Also

	 * determines if shaping needs to occur between figures and sets the

	 * appendJoiner, prependJoiner accordingly.

	 * 

	 * @param levels

	 *            the calculated levels of all the text in the block

	 */

	private void assignResults(int[] levels) {

		BidiEntry prevEntry = null, entry = null;

		BidiInfo prevInfo = null, info = null;

		int end = 2, start = 0;

		for (int i = 0; i < list.size(); i++) {

			entry = (BidiEntry) list.get(i);

			info = new BidiInfo();

			while (levels[end] < entry.end)

				end += 2;

			int levelInfo[];

			if (end == start) {

				levelInfo = new int[1];

				if (prevInfo != null)

					levelInfo[0] = prevInfo.levelInfo[prevInfo.levelInfo.length - 1];

				else

					levelInfo[0] = (orientation == SWT.LEFT_TO_RIGHT) ? 0 : 1;

			} else {

				levelInfo = new int[end - start - 1];

				System.arraycopy(levels, start + 1, levelInfo, 0,

						levelInfo.length);

			}

			for (int j = 1; j < levelInfo.length; j += 2)

				levelInfo[j] -= entry.begin;

			info.levelInfo = levelInfo;

			// Compare current and previous for joiners, and commit previous

			// BidiInfo.

			if (prevEntry != null) {

				if (// if we started in the middle of a level run

				levels[start] < entry.begin

				// and the level run is odd

						&& levels[start + 1] % 2 == 1

						// and the first character of this figure is Arabic

						&& isJoiner(entry.begin)

						// and the last character of the previous figure was

						// Arabic

						&& isPrecedingJoiner(entry.begin))

					prevInfo.trailingJoiner = info.leadingJoiner = true;

				prevEntry.fig.setBidiInfo(prevInfo);

			}

			prevEntry = entry;

			prevInfo = info;

			if (entry.end == levels[end])

				start = end;

			else

				start = end - 2;

		}

		if (entry != null)

			entry.fig.setBidiInfo(info);

	}

	private boolean isJoiner(int begin) {

		return begin < bidiText.length()

				&& isJoiningCharacter(bidiText.charAt(begin));

	}

	/**

	 * @param the

	 *            character to be evaluated

	 * @return <code>true</code> if the given character is Arabic or ZWJ

	 */

	private boolean isJoiningCharacter(char c) {

		return Character.getDirectionality(c) == Character.DIRECTIONALITY_RIGHT_TO_LEFT_ARABIC

				|| c == BidiChars.ZWJ;

	}

	private boolean isPrecedingJoiner(int begin) {

		return begin > 0 && isJoiningCharacter(bidiText.charAt(begin - 1));

	}

	/**

	 * Processes the contributed text, determines the Bidi levels, and assigns

	 * them to the FlowFigures that made thet contributions. This class is for

	 * INTERNAL use only. Shaping of visually contiguous Arabic characters that

	 * are split in different figures is also handled. This method will do

	 * nothing if the contributed text does not require Bidi evaluation. All

	 * contributions are discarded at the end of this method.

	 */

	public void process() {

		try {

			if (bidiText.length() == 0 || isMacOS)

				return;

			char[] chars = new char[bidiText.length()];

			bidiText.getChars(0, bidiText.length(), chars, 0);

			//Not supported in RAP

			// if (orientation != SWT.RIGHT_TO_LEFT

			// && !Bidi.requiresBidi(chars, 0, chars.length - 1))

			// return;

			int[] levels = new int[15];

			TextLayout layout = FlowUtilities.getTextLayout();

			layout.setOrientation(orientation);

			layout.setText(bidiText.toString());

			int j = 0, offset, prevLevel = -1;

			for (offset = 0; offset < chars.length; offset++) {

				int newLevel = layout.getLevel(offset);

				if (newLevel != prevLevel) {

					if (j + 3 > levels.length) {

						int temp[] = levels;

						levels = new int[levels.length * 2 + 1];

						System.arraycopy(temp, 0, levels, 0, temp.length);

					}

					levels[j++] = offset;

					levels[j++] = newLevel;

					prevLevel = newLevel;

				}

			}

			levels[j++] = offset;

			if (j != levels.length) {

				int[] newLevels = new int[j];

				System.arraycopy(levels, 0, newLevels, 0, j);

				levels = newLevels;

			}

			assignResults(levels);

			// reset the orientation of the layout, in case it was set to RTL

			layout.setOrientation(SWT.LEFT_TO_RIGHT);

		} finally {

			// will cause the fields to be reset for the next string to be

			// processed

			bidiText = null;

			list.clear();

		}

	}

	/**

	 * Sets the paragraph embedding. The given orientation will be used on

	 * TextLayout when determining the Bidi levels.

	 * 

	 * @param newOrientation

	 *            SWT.LEFT_TO_RIGHT or SWT.RIGHT_TO_LEFT

	 */

	public void setOrientation(int newOrientation) {

		bidiText = new StringBuffer();

		list.clear();

		orientation = newOrientation;

	}

}