Mouse hit and textlayout : Text Layout « 2D Graphics GUI « Java

Mouse hit and textlayout

Mouse hit and textlayout

import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Shape;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.awt.font.FontRenderContext;
import java.awt.font.TextAttribute;
import java.awt.font.TextHitInfo;
import java.awt.font.TextLayout;
import java.awt.geom.Point2D;
import java.text.AttributedCharacterIterator;
import java.text.AttributedString;
import java.util.Hashtable;

import javax.swing.JFrame;
import javax.swing.JPanel;

public class HitTestSample extends JPanel {
  private static final Color STRONG_CARET_COLOR =;

  private static final Color WEAK_CARET_COLOR =;

  private TextLayout textLayout;

  private int insertionIndex;

  private static final FontRenderContext DEFAULT_FRC = new FontRenderContext(
      null, false, false);

  private static final Hashtable map = new Hashtable();
  static {
    map.put(TextAttribute.SIZE, new Float(18.0));

  private static AttributedString helloWorld = new AttributedString(
      "Java Source and Support.", map);

  public HitTestSample() {
    AttributedCharacterIterator text = helloWorld.getIterator();
    // Create a new TextLayout from the given text.
    textLayout = new TextLayout(text, DEFAULT_FRC);

    // Initilize insertionIndex.
    insertionIndex = 0;

    addMouseListener(new HitTestMouseListener());

  public Dimension getPreferredSize() {
    return new Dimension(400, 250);

  private Point2D computeLayoutOrigin() {

    Dimension size = getPreferredSize();
    Point2D.Float origin = new Point2D.Float();

    origin.x = (float) (size.width - textLayout.getAdvance()) / 2;
    origin.y = (float) (size.height - textLayout.getDescent() + textLayout
        .getAscent()) / 2;
    return origin;

  public void paintComponent(Graphics g) {
    Graphics2D graphics2D = (Graphics2D) g;

    Point2D origin = computeLayoutOrigin();

    graphics2D.translate(origin.getX(), origin.getY());

    // Draw textLayout.
    textLayout.draw(graphics2D, 0, 0);

    // Retrieve caret Shapes for insertionIndex.
    Shape[] carets = textLayout.getCaretShapes(insertionIndex);


    if (carets[1] != null) {

  private class HitTestMouseListener extends MouseAdapter {
    public void mouseClicked(MouseEvent e) {

      Point2D origin = computeLayoutOrigin();

      // Compute the mouse click location relative to
      // textLayout's origin.
      float clickX = (float) (e.getX() - origin.getX());
      float clickY = (float) (e.getY() - origin.getY());

      // Get the character position of the mouse click.
      TextHitInfo currentHit = textLayout.hitTestChar(clickX, clickY);
      insertionIndex = currentHit.getInsertionIndex();

      // Repaint the Component so the new caret(s) will be displayed.

  public static void main(String[] args) {

    JFrame f = new JFrame("HitTestSample");
    HitTestSample demo = new HitTestSample();
    f.getContentPane().add(demo, "Center");

    f.addWindowListener(new WindowAdapter() {
      public void windowClosing(WindowEvent e) {

    f.setSize(new Dimension(400, 250));


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