Swing Hacks

Write Backward Text #51

Chapter 7, Text

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273

HACK

Messing with JLabel

The easiest text component to distort is the simple JLabel. The

BackwardsJLabel class in Example 7-6 subclasses JLabel and uses an

AffineTransform

in the

paint( )

method to do the flip.

The constructors make trivial calls to their parent classes, so the key is the

overridden

paint( ) method. It first checks that you have a Graphics2D and

does the cast. Any

Graphics2D has an AffineTransformation that defines

transforms that are to be applied as the

Graphics2D is rendered. The

AffineTransform of a Component will usually have some important transforms

already defined in it, so it’s best not to replace its transform, but rather to use

the

Graphics2D.transform( ) method to modify the existing AffineTransform

with one of your own making.

But what kind of transform do you want to do? A mirror image consists of

two separate transformations: scaling the x-coordinates by a factor of -1

Example 7-6. Rendering a JLabel as a mirror image

import java.awt.*;

import javax.swing.*;

import java.awt.geom.*;

import javax.swing.text.Document;

public class BackwardsJLabel extends JLabel {

public BackwardsJLabel () { super( ); }

public BackwardsJLabel (Icon image) {super (image);}

public BackwardsJLabel (Icon image, int align) {super (image, align);}

public BackwardsJLabel (String text) { super (text);}

public BackwardsJLabel (String text, Icon icon, int align) {

super (text, icon, align);

}

public BackwardsJLabel (String text, int align) { super (text, align);}

public void paint (Graphics g) {

if (g instanceof Graphics2D) {

Graphics2D g2 = (Graphics2D) g;

AffineTransform flipTrans = new AffineTransform( );

double widthD = (double) getWidth( );

flipTrans.setToTranslation (widthD, 0);

flipTrans.scale (-1.0, 1);

g2.transform (flipTrans);

super.paint(g);

} else {

super.paint(g);

}

}

}