Fancier 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
*/
// FancyCaret.java
//Another (fancier) 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 FancyCaret extends DefaultCaret {
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;
height = r.height;
// A value for width was probably set by paint(), which we leave alone.
// But the first call to damage() precedes the first call to paint(), so
// in this case we must be prepared to set a valid width, or else
// paint()
// will receive a bogus clip area and caret will not get drawn properly.
if (width <= 0)
width = getComponent().getWidth();
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;
char dotChar;
try {
r = comp.modelToView(dot);
if (r == null)
return;
dotChar = comp.getText(dot, 1).charAt(0);
} catch (BadLocationException e) {
return;
}
if ((x != r.x) || (y != r.y)) {
// 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; // Update dimensions (width gets set later in this method)
y = r.y;
height = r.height;
}
g.setColor(comp.getCaretColor());
g.setXORMode(comp.getBackground()); // do this to draw in XOR mode
if (dotChar == '\n') {
int diam = r.height;
if (isVisible())
g.fillArc(r.x - diam / 2, r.y, diam, diam, 270, 180); // half
// circle
width = diam / 2 + 2;
return;
}
if (dotChar == '\t')
try {
Rectangle nextr = comp.modelToView(dot + 1);
if ((r.y == nextr.y) && (r.x < nextr.x)) {
width = nextr.x - r.x;
if (isVisible())
g.fillRoundRect(r.x, r.y, width, r.height, 12, 12);
return;
} else
dotChar = ' ';
} catch (BadLocationException e) {
dotChar = ' ';
}
width = g.getFontMetrics().charWidth(dotChar);
if (isVisible())
g.fillRect(r.x, r.y, width, r.height);
}
public static void main(String args[]) {
JFrame frame = new JFrame("FancyCaret demo");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JTextArea area = new JTextArea(8, 32);
area.setCaret(new FancyCaret());
area.setText("VI\tVirgin Islands \nVA Virginia\nVT\tVermont");
frame.getContentPane().add(new JScrollPane(area), BorderLayout.CENTER);
frame.pack();
frame.setVisible(true);
}
}
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