Name: jk109818 Date: 07/29/2002


FULL PRODUCT VERSION :
java version "1.4.0"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.4.0-b92)
Java HotSpot(TM) Client VM (build 1.4.0-b92, mixed mode)

FULL OPERATING SYSTEM VERSION : Windows NT Version 4.0


ADDITIONAL OPERATING SYSTEMS : probably all



A DESCRIPTION OF THE PROBLEM :
In our case, a JTree is contained in a JScrollPane. A
custom TransferHandler is installed to allow drag-and-drop
within the JTree to move nodes.

If the JScrollPane is scrolled all the way to the top of
the tree, dragging a tree node down to the bottom of the
JScrollPane does not initiate autoscroll.

If the JScrollPane is scrolled to the middle of the tree,
dragging a node to the top or bottom causes autoscroll, but
the scroll increments are incorrect.

The cause: The direction constants are reversed in calls
to getScrollableUnitIncrement() in both
updateAutoscrollRegion() and autoScroll() in class
javax.swing.plaf.basic.BasicDropTargetListener. "1" should
be "-1" and "-1" should be "1".

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
1. Run the demo source code attached.
2. Click a tree node to select it.
3. Drag the node to the bottom of the frame.
--> no autoscroll.
4. Release the node.
5. Scroll the tree down a small ways
6. Drag the node to the bottom of the frame again.
--> now autoscrolls, but scroll increment is incorrect.

EXPECTED VERSUS ACTUAL BEHAVIOR :
In steps above.

This bug can be reproduced always.

---------- BEGIN SOURCE ----------
import java.awt.*;
import java.awt.datatransfer.*;
import javax.swing.*;

class AutoscrollDemo extends javax.swing.JFrame {
public AutoscrollDemo() {
String[] nodes = new String[30];
for (int i=0; i<nodes.length; i++)
nodes[i] = "# " + i;
JTree tree = new JTree (nodes);
JScrollPane scrollPane = new JScrollPane (tree);
getContentPane().add (BorderLayout.CENTER, scrollPane);
tree.setVisibleRowCount(12);
tree.setTransferHandler(new MyTransferHandler());
tree.setDragEnabled(true);
pack();
setVisible(true);
}

class MyTransferHandler extends javax.swing.TransferHandler {
     public int getSourceActions (JComponent c) {
         return TransferHandler.COPY_OR_MOVE;
     }
     public boolean canImport(JComponent comp, DataFlavor transferFlavors[])
{
     return true; // allow drops
}
     public Transferable createTransferable (JComponent comp) {
     return new StringSelection ("testing");
}
}

static public void main(String args[]) {
new AutoscrollDemo();
}
}

---------- END SOURCE ----------
(Review ID: 143592)
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