CellRendererPane causes c

  To: comp.lang.java.gui
Hi there,

I have a nasty bug that I worked on for a couple of days already and I
finally managed to isolate the problem. It seems that the use of a
CellRendererPane causes the mouse cursor to flicker during drag and
drop, but only if the "validate" flag is set to true. This effect
seems to happen on Windows only (Mac works fine). I am using Windows
XP. I have written a little standalone test case that you can find
below. Simply initiate a drag and drop sequence from one panel to
another and play around with the checkbox in the upper left corner. If
selected, the renderer component that draws the button will be
validated before its paint method gets called. When this happens the
cursor starts to flicker.

I would appreciate it very much if anyone could tell me how to get rid
of this problem. My renderer components are often quite complex and I
need to have them validated before calling them, so setting "validate"
to false does not work for me.

--Dirk
www.dlsc.com

package com.dlsc.test;
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.datatransfer.DataFlavor;
import java.awt.datatransfer.Transferable;
import java.awt.datatransfer.UnsupportedFlavorException;
import java.awt.dnd.DnDConstants;
import java.awt.dnd.DragGestureEvent;
import java.awt.dnd.DragGestureListener;
import java.awt.dnd.DragSource;
import java.awt.dnd.DragSourceDragEvent;
import java.awt.dnd.DragSourceDropEvent;
import java.awt.dnd.DragSourceEvent;
import java.awt.dnd.DragSourceListener;
import java.awt.dnd.DropTarget;
import java.awt.dnd.DropTargetDragEvent;
import java.awt.dnd.DropTargetDropEvent;
import java.awt.dnd.DropTargetEvent;
import java.awt.dnd.DropTargetListener;
import java.io.IOException;

import javax.swing.CellRendererPane;
import javax.swing.JButton;
import javax.swing.JCheckBox;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
import javax.swing.border.TitledBorder;

public class DnDTestFrame extends JFrame {
private JCheckBox checkBox = new JCheckBox("Cell renderer validates",
true);

public DnDTestFrame() {
super("DnDTest");

add(BorderLayout.NORTH, checkBox);
add(BorderLayout.WEST,new DnDTestPanel("Left", this));
add(BorderLayout.EAST,new DnDTestPanel("Right", this));
pack();
setVisible(true);
}

public boolean isValidating() {
return checkBox.isSelected();
}

/**
* @param args
*/
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
new DnDTestFrame();
}
});
}
}

class DnDTestPanel extends JPanel implements DragGestureListener,
DragSourceListener, DropTargetListener {

private String title;
private CellRendererPane rendererPane = new CellRendererPane();
private JButton rendererComp = new JButton("Renderer");
private DnDTestFrame frame;

public DnDTestPanel(String title, DnDTestFrame frame) {
this.title = title;
this.frame = frame;

setLayout(null);
add(rendererPane);

setBackground(Color.WHITE);
setPreferredSize(new Dimension(300, 300));
setBorder(new TitledBorder(title));
DragSource.getDefaultDragSource().createDefaultDragGestureRecognizer(
this, DnDConstants.ACTION_COPY_OR_MOVE, this);
new DropTarget(this, DnDConstants.ACTION_COPY_OR_MOVE, this);
}

@Override
protected void paintComponent(Graphics g) {
rendererPane.paintComponent(g, rendererComp, this, 20, 20, 100, 30,
frame.isValidating());
}

public void dragGestureRecognized(DragGestureEvent dge) {
dge.startDrag(null, new Transferable() {

public Object getTransferData(DataFlavor flavor)
throws UnsupportedFlavorException, IOException {
return null;
}

public DataFlavor[] getTransferDataFlavors() {
return new DataFlavor[] { DataFlavor.plainTextFlavor };
}

public boolean isDataFlavorSupported(DataFlavor flavor) {
return true;
}
});
}

// drag source
public void dragDropEnd(DragSourceDropEvent dsde) {
}

public void dragEnter(DragSourceDragEvent dsde) {
}

public void dragExit(DragSourceEvent dse) {
}

public void dragOver(DragSourceDragEvent dsde) {
}

public void dropActionChanged(DragSourceDragEvent dsde) {
}

// drop target
public void dragEnter(DropTargetDragEvent dtde) {
repaint();
}

public void dragExit(DropTargetEvent dte) {
repaint();
}

public void dragOver(DropTargetDragEvent dtde) {
repaint();
}

public void drop(DropTargetDropEvent dtde) {
}

public void dropActionChanged(DropTargetDragEvent dtde) {
}
}

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