src/com/ibm/text/components/TransliteratingTextComponent.java

package com.ibm.text.components;

import java.awt.*;
import java.awt.event.*;
import java.text.*;
import java.awt.datatransfer.*;
import com.ibm.text.*;

/**
 * A subclass of {@link DumbTextComponent} that passes key events through
 * a {@link com.ibm.text.Transliterator}.
 *
 * <p>Copyright &copy; IBM Corporation 1999.  All rights reserved.
 *
 * @author Alan Liu
 * @version $RCSfile: TransliteratingTextComponent.java,v $ $Revision: 1.1 $ $Date: 1999/12/20 18:29:21 $
 */
public class TransliteratingTextComponent extends DumbTextComponent {

    private static boolean DEBUG = false;

    private Transliterator translit = null;

    // Index into getText() where the start of transliteration is.
    // As we commit text during keyboardTransliteration, we advance
    // this.
    private int start = 0;

    // Index into getText() where the cursor is; cursor >= start
    private int cursor = 0;

    private static final String COPYRIGHT =
        "\u00A9 IBM Corporation 1999. All rights reserved.";

    /**
     * Constructor.
     */
    public TransliteratingTextComponent() {
        super();
        addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                // We get an ActionEvent only when the selection changes
                resetTransliterationStart();
            }
        });
    }

    /**
     * {@link DumbTextComponent} API.  Framework method that is called
     * when a <code>KeyEvent</code> is received.  This implementation
     * runs the new character through the current
     * <code>Transliterator</code>, if one is set, and inserts the
     * transliterated text into the buffer.
     */
	protected void handleKeyTyped(KeyEvent e) {
        char ch = e.getKeyChar();

        if (translit == null) {
            super.handleKeyTyped(e);
            return;
        }

        // ------------------------------------------------------------
        // The following case motivates the two lines that recompute
        // start and cursor below.

        //      "     "   
        // a b c q r|s t u m m
        // 0 1 2 3 4 5 6 7 8 9
        //       0 1 2

        // start 3, cursor 5, sel 6 -> { 0, 3, 2 }
        // : new int[] { 0, sel - start, cursor - start };
        
        // sz>99|9

        //      "     {   "
        // a b c q r 9 9|9 t u m m
        // 0 1 2 3 4 5 6 7 8 9 a b
        //       0 1 2 3 4

        // { 3, 5, 4 } -> start 6, cursor 7, sel 8
        // : start += index[0];
        // : cursor = start + index[2] - index[0];
        // ------------------------------------------------------------

        // Need to save start because calls to replaceRange will update
        // start and cursor.
        int saveStart = start;

        ReplaceableString buf = new ReplaceableString();
        buf.getStringBuffer().append(getText().substring(start,
                                                         getSelectionStart()));

        int[] index = new int[] { 0, getSelectionStart() - start,
                                  cursor - start};

        StringBuffer log = null;
        if (DEBUG) {
            log = new StringBuffer();
            log.append("start " + start + ", cursor " + cursor);
            log.append(", sel " + getSelectionStart());
            log.append(", {" + index[0] + ", " + index[1] + ", " + index[2] + "}, ");
            log.append('"' + buf.toString() + "\" + '" + ch + "' -> \"");
        }

        translit.keyboardTransliterate(buf, index, ch);
        replaceRange(buf.toString(), start, getSelectionEnd());
        // At this point start has been changed by the callback to
        // resetTransliteratorStart() via replaceRange() -- so use our
        // local copy, saveStart.

        // The START index is zero-based.  On entry to keyboardTransliterate(),
        // it was zero.  We can therefore just add it to our original
        // getText()-based index value of start (in saveStart) to get
        // the new getText()-based start.
        start = saveStart + index[Transliterator.START];

        // Make the cursor getText()-based.  The CURSOR index is zero-based.
        cursor = start + index[Transliterator.CURSOR]
            - index[Transliterator.START];

        if (DEBUG) {
            String out = buf.toString();
            log.append(out.substring(0, index[Transliterator.START])).
                append('{').
                append(out.substring(index[Transliterator.START],
                                     index[Transliterator.CURSOR])).
                append('|').
                append(out.substring(index[Transliterator.CURSOR])).
                append('"');
            log.append(", {" + index[0] + ", " + index[1] + ", " + index[2] + "}, ");
            log.append("start " + start + ", cursor " + cursor);
            log.append(", sel " + getSelectionStart());
            System.out.println(escape(log.toString()));
        }
    }

    /**
     * Set the {@link com.ibm.text.Transliterator} and direction to
     * use to process incoming <code>KeyEvent</code>s.
     * @param t the {@link com.ibm.text.Transliterator} to use
     */
    public void setTransliterator(Transliterator t) {
        if (translit != t) { // [sic] pointer compare ok; singletons
            resetTransliterationStart();
        }
        translit = t;
    }

    /**
     * Reset the start point at which transliteration begins.  This
     * needs to be done when the user moves the cursor or when the
     * current {@link com.ibm.text.Transliterator} is changed. 
     */
    private void resetTransliterationStart() {
        start = getSelectionStart();
        cursor = start;
    }

    /**
     * Escape non-ASCII characters as Unicode.
     * JUST FOR DEBUGGING OUTPUT.
     */
    public static final String escape(String s) {
        StringBuffer buf = new StringBuffer();
        for (int i=0; i<s.length(); ++i) {
            char c = s.charAt(i);
            if (c >= ' ' && c <= 0x007F) {
                if (c == '\\') {
                    buf.append("\\\\"); // That is, "\\"
                } else {
                    buf.append(c);
                }
            } else {
                buf.append("\\u");
                if (c < 0x1000) {
                    buf.append('0');
                    if (c < 0x100) {
                        buf.append('0');
                        if (c < 0x10) {
                            buf.append('0');
                        }
                    }
                }
                buf.append(Integer.toHexString(c));
            }
        }
        return buf.toString();
    }
}