[java2d] transform problem w/ rectangle (jdk1.2.1)

[Ralph E. LaChance]

Hello,

We're seeing some weirdness in translating (we think)
a rectangle. Our example is trivial -- perhaps we got
it wrong.  Any ideas?

Attached code, draws one rectangle and 3 ellipses,
intended to demonstrate dragging an area around 
a small canvas.  

The behavior is decidedly different for the rectangle
in this demo than than for the ellipses.  Pick and drag 
the ellipses, they move and drop into a new position;
pick and drag the rectangle, it moves, but when dropped
it redraws in its old position, and (at first blush) seems
not to be pick-able anymore.

In fact, after  dropping,  the rectangle, has "moved"
to the new location -- it can be picked from the hidden
drop point and dragged again -- but it always redraws 
at the original location....

We'd be happy for any guidance.  Thanks in advance.
        
        'best
        -Ralph LaChance
        
        (Friday, May 21, 1999,  1:38 PM)

------------------ the code ------------------ 

import java.awt.*;
import java.awt.event.*;
import java.awt.geom.*;

public class Mover extends Frame 
{
    public static void main(String[] arg) 
    {
        new Mover();
    }

    Mover() 
    {
        super("Mover");
        addWindowListener(new WindowAdapter() {
            public void windowClosing(WindowEvent e)
                { System.exit(0); } } );
        MoverPanel mp = new MoverPanel();
        add(mp);
        pack();
        show();
    }

class MoverPanel extends Canvas
        implements MouseListener, MouseMotionListener 
{
    boolean moving = false ;
    int moveIndex = -1 ;
    int startx ;
    int starty ;
    int endx ;
    int endy ;
    Image offscreen = null ;
    Area[] area ;
    AffineTransform at ;
    BasicStroke dashes ;
    BasicStroke solid ;


    MoverPanel() 
    {
        addMouseListener(this);
        addMouseMotionListener(this);
        area = new Area[4];
//
//      alternate code, all ellipses
// 
//    area[0] = new Area (new Ellipse2D.Float  (10,10,40,40));
//
        area[0] = new Area (new Rectangle2D.Float(10,10,40,40));
        area[1] = new Area (new Ellipse2D.Float  (80,80,20,50));
        area[2] = new Area (new Ellipse2D.Float  (130,130,60,60));
        area[3] = new Area (new Ellipse2D.Float  (200,200,50,20));

        setSize(300,250);
        at = new AffineTransform();
        float[] pattern = { 5f,5f };
        dashes = new BasicStroke(1f,BasicStroke.CAP_BUTT,
        BasicStroke.JOIN_BEVEL,1f,pattern,0f);
        solid  = new BasicStroke(1f,BasicStroke.CAP_BUTT,
                BasicStroke.JOIN_BEVEL);
    }


    // null out offscreen buffer as part of invalidation
    public void invalidate()
    {
        super.invalidate() ;
        offscreen = null ;
    }

    // override to *not* erase background before painting
    public void update (Graphics g)
    {
         paint (g) ;
    }


    public void paint(Graphics g) 
    {
        if (offscreen == null)
          offscreen = createImage (getSize().width, getSize().height);

        Graphics2D g2 = (Graphics2D) offscreen.getGraphics() ;
        g2.setClip (0,0,getSize().width, getSize().height) ;
        super.paint (g2) ;

        for(int i=0; i<area.length; i++)
          {
            g2.setColor (i==moveIndex ? Color.yellow : Color.red) ;
                    g2.fill(area[i]) ;
            g2.setColor (Color.black) ;
                    g2.setStroke(solid) ;
                    g2.draw(area[i]) ;
                }

                if(moving) 
          {
                     g2.setTransform(at);
                     g2.setStroke(dashes);
             g2.setColor (Color.blue) ;
                     g2.draw(area[moveIndex]) ;
          }

        ((Graphics2D)g).drawImage (offscreen, 0,0, null) ;
        g2.dispose() ;

    }
    public void mouseMoved(MouseEvent event) 
    {
        moving = false;
        moveIndex = -1 ;
    }

    public void mouseDragged(MouseEvent event) 
    {
        if(!moving)
            return;

        endx = event.getX() ;
        endy = event.getY() ;
        at.setToTranslation(endx - startx,endy - starty) ;
        repaint() ;
    }

    public void mousePressed(MouseEvent event) 
    {
        moving = false ;
        startx = event.getX() ;
        starty = event.getY() ;

        // hit detect in reverse of draw order to get top/bottom effect
        for(int i=area.length - 1; i>=0; i--) 
          {
            if(area[i].contains(startx,starty)) 
              {
                moving = true ;
                moveIndex = i ;
                at.setToTranslation(0,0) ;
                break ;
              }
          }
    }
    public void mouseReleased(MouseEvent event) 
    {
        if(moving) 
          {
            area[moveIndex].transform(at) ;
            moving = false ;
            moveIndex = -1 ;
            repaint() ;
          }
    }
    public void mouseEntered (MouseEvent event) { }
    public void mouseExited  (MouseEvent event) { }
    public void mouseClicked (MouseEvent event) { }
}
}

------------------  end of code  ------------------ 


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