A custom caret class
/*
Java Swing, 2nd Edition
By Marc Loy, Robert Eckstein, Dave Wood, James Elliott, Brian Cole
ISBN: 0-596-00408-7
Publisher: O'Reilly
*/
// CornerCaret.java
//A custom caret class.
//
import java.awt.BorderLayout;
import java.awt.Graphics;
import java.awt.Rectangle;
import javax.swing.JFrame;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.text.BadLocationException;
import javax.swing.text.DefaultCaret;
import javax.swing.text.JTextComponent;
public class CornerCaret extends DefaultCaret {
public CornerCaret() {
setBlinkRate(500); // half a second
}
protected synchronized void damage(Rectangle r) {
if (r == null)
return;
// give values to x,y,width,height (inherited from java.awt.Rectangle)
x = r.x;
y = r.y + (r.height * 4 / 5 - 3);
width = 5;
height = 5;
repaint(); // calls getComponent().repaint(x, y, width, height)
}
public void paint(Graphics g) {
JTextComponent comp = getComponent();
if (comp == null)
return;
int dot = getDot();
Rectangle r = null;
try {
r = comp.modelToView(dot);
} catch (BadLocationException e) {
return;
}
if (r == null)
return;
int dist = r.height * 4 / 5 - 3; // will be distance from r.y to top
if ((x != r.x) || (y != r.y + dist)) {
// paint() has been called directly, without a previous call to
// damage(), so do some cleanup. (This happens, for example, when
// the
// text component is resized.)
repaint(); // erase previous location of caret
x = r.x; // set new values for x,y,width,height
y = r.y + dist;
width = 5;
height = 5;
}
if (isVisible()) {
g.setColor(comp.getCaretColor());
g.drawLine(r.x, r.y + dist, r.x, r.y + dist + 4); // 5 vertical
// pixels
g.drawLine(r.x, r.y + dist + 4, r.x + 4, r.y + dist + 4); // 5 horiz
// px
}
}
public static void main(String args[]) {
JFrame frame = new JFrame("CornerCaret demo");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JTextArea area = new JTextArea(8, 32);
area.setCaret(new CornerCaret());
area
.setText("This is the story\nof the hare who\nlost his spectacles.");
frame.getContentPane().add(new JScrollPane(area), BorderLayout.CENTER);
frame.pack();
frame.setVisible(true);
}
}
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