When printing, HotJava will frequently get a ClassCastException on calling
java.awt.Component.printAll(java.awt.Graphics). It appears that AWT
(in native code) is attempting to cast java.awt.Graphics down to
java.awt.PrintGraphics. This cannot be done, because the API of
Component explicitly supports any kind of Graphics object.

HotJava calls Component.printAll() with a subclass of Graphics that is
not a subclass of PrintGraphics for very good reason: When an applet
(or some other fixed-width entity) is wider than the available width
of the paper, HotJava creates a sunw.hotjava.misc.ScalingGraphics, which
delegates all of its calls to the real Graphics object, after suitable
scaling.

To reproduce: Launch HotJava, and go to
http://javaweb.eng/~billf/bugs/4084040/ . HotJava is swallowing
the exception (in this case, in TagAppletPanel, around line 472:

                Applet applet = getApplet();
                if (applet != null) {
                    applet.printAll(g);
                }
            }
        } catch (Exception ignored) {
            // If the applet fails to print, we should go on with the
            // rest of the print job. This also works around bug 4084040.
        } finally {
            if (sg != null) {
                sg.setTryToScaleFonts(wasScalingFonts);
            }
        }



Here's a stack backtrace that demonstrates the problem:

java.lang.ClassCastException: sunw.hotjava.misc.ScalingGraphics
        at
        at java.awt.Component.printAll(Component.java:1395)
        at java.awt.Container.printComponents(Container.java:837)
        at sun.awt.windows.WPanelPeer.print(WPanelPeer.java:33)
        at java.awt.Component.printAll(Component.java:1395)
        at sunw.hotjava.forms.SELECT.print(SELECT.java:143)
        at sunw.hotjava.doc.Formatter.printLine(Formatter.java:2012)
        at sunw.hotjava.tables.TableElementFormatter.print(TableElementFormatter.java:646)
        at sunw.hotjava.tables.TableElementPanel.print(TableElementPanel.java:164)
        at sunw.hotjava.tables.TablePanel.printTableElement(TablePanel.java:1052)
        at sunw.hotjava.tables.TablePanel.print(TablePanel.java:1035)
        at sunw.hotjava.tables.TABLE.print(TABLE.java:247)
        at sunw.hotjava.doc.Formatter.printLine(Formatter.java:2012)
        at sunw.hotjava.tables.TableElementFormatter.print(TableElementFormatter.java:646)
        at sunw.hotjava.tables.TableElementPanel.print(TableElementPanel.java:164)
        at sunw.hotjava.tables.TablePanel.printTableElement(TablePanel.java:1052)
        at sunw.hotjava.tables.TablePanel.print(TablePanel.java:1035)
        at sunw.hotjava.tables.TABLE.print(TABLE.java:247)
        at sunw.hotjava.doc.Formatter.printLine(Formatter.java:2012)
        at sunw.hotjava.doc.DocumentFormatter.printPages(DocumentFormatter.java: 2271)
        at sunw.hotjava.doc.DocumentFormatter.print(DocumentFormatter.java:2110)
        at sunw.hotjava.doc.DocumentPanel.print(DocumentPanel.java:469)
        at sunw.hotjava.doc.MasterDocumentPanel.run(MasterDocumentPanel.java:627)
        at java.lang.Thread.run(Thread.java:474)


Name: krT82822 Date: 06/28/99


When passing a Graphics context, not a PrintGraphics, to the print() method a class cast exception is thrown in JDK1.2.1 and not in JDK1.1.

The code launches a Frame with two buttons, this first prints the screen, the second attempts to display a "print preview" in a second frame. The code works fine in JDK1.1.x and throws and exception in JDK1.2.1.

Code that exhibits the problem, 2 classes printPanel and imagePanel.
---------------------------------------------
import java.awt.*;
import java.awt.event.*;


public class printPanel extends Panel implements ActionListener
{
private Image imgBuffer;
private Graphics gBuffer;

Button btnPrint;
Button btnPrintPreview;

public printPanel()
{
btnPrint = new Button( "Print" );
btnPrintPreview = new Button( "Print Preview" );

this.add( btnPrint );
this.add( btnPrintPreview );

btnPrint.addActionListener( this );
btnPrintPreview.addActionListener( this );
}

public void actionPerformed( ActionEvent e )
{
Object o = e.getSource();
if ( o.equals( btnPrint ) )
{
PrintJob pj = this.getToolkit().getPrintJob( (Frame) this.getParent(), "Test Job", null);
      this.printAll( pj.getGraphics() );
     pj.end();
}
else if ( o.equals( btnPrintPreview ) )
{
Frame fr = new Frame( "Print Preview" );
imagePanel ip = new imagePanel();
fr.add( ip );
fr.setBounds( 20,20, 150, 100 );

//this.paintAll( gBuffer ); // <- doesn't throw an exception, but doesn't paint "heavy" components
this.printAll( gBuffer ); // <- throws a ClassCastException

ip.setImage( imgBuffer );
fr.show();
}

}


public void reshape(int x, int y, int width, int height)
{
super.reshape( x, y, width, height );
if ( width>0 && height>0 )
imgBuffer = createImage( width, height);

if (imgBuffer != null)
gBuffer = imgBuffer.getGraphics();
}

public static void main(String[] astr)
{
String strTitle = "Print Panel";

Frame fr=new Frame( strTitle );
printPanel pp = new printPanel();
    

fr.add(pp);
fr.setBounds( 20,20, 150, 100 );
fr.show();
}
}

-------------------------

import java.awt.*;

public class imagePanel extends Panel
{
private Image _img = null;

public void setImage( Image img )
{
_img = img;
repaint( 0, 0, _img.getWidth(this), img.getHeight(this));
}

public void paint(Graphics g)
{
if ( _img != null )
g.drawImage( _img, 0, 0, this );

super.paint( g );
}
}
(Review ID: 84862)
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