DnD fails with JTextArea and JTextField (original) (raw)

Pavel Porvatov pavel.porvatov at oracle.com
Tue Sep 13 09:54:19 UTC 2011

Hi Sean,

Hi Pavel ,

I'm sorry I didn't make update for this bug for a long time, and here is some recent investigation. The scenario is as follows: Suppose we are dragging "abcde" over TextField tf, which have "hello dragging" as its content. When we are dragging from start to end, there is a cursor moving from "h" to "g", which means the place to insert "abcde" if we drop it. When we dragging "abcde" exit tf, there will be a dragExit event, the tf needs to restore its original status after we drag out. Eg. if its cursor is between "h" and "e" in "hello", which appears like "h|ello", when we are dragging over it, it may like "hello dr|agging", and when drag exit, it needs to be "h|ello" again. So in dragExit handler, it calls javax.swing.TransferHandler.cleanup(false), which means only to restore the original state. cleanup calls javax.swing.text.JTextComponent.setDropLocation to set the cursor to original position. And setDropLocation calls DefaultCaret.setDot and DefaultCaret.moveDot to set the state. The problem is moveDot doesn't know this is just to restore the original state, it treats the invocation as an action to select something. And it calls updateSystemSelection which will call java.awt.datatransfer.Clipboard.setContent. And the selected content is changed from "abcde" to the original selected part of "hello dragging", then the drop operation finds it is not the string dragged and nothing is dropped. So I made a simple patch(attached) . It just check if the textField owns focus before updateSystemSelection, if it is not focused, it does not treat the moveDot as a selection action and does not call Clipboard.setContent. This works on Linux, however, DefaultCaret is shared by Linux and Windows while windows doesn't have this problem. So I don't think this is a correct patch, but it brings my question. I think it is strange for DefaultCaret to use setDot and moveDot to restore original state, especially moveDot will cause an updateSystemSelection operation, which makes moveDot much like an action from user instead of just restoring state. I'm not sure why it works well on windows, but I don't think it is right to call updateSystemSelection or it is not right to use setDot and moveDot to restore the original state. Is there any reason for that ? Thanks for the patch! I believe you are right and we shouldn't update system selection clipboard when the component doesn't have focus. I'd like to modify your fix and move checking into the DefaultCaret#updateSystemSelection method: if (this.dot != this.mark && component != null && component.hasFocus()) {

We also must write regression tests for fixes if possible, so an automatic test is needed as well. Could you please write a test for the fix?

I'm not sure why it works well on windows, That's because Windows doesn't have system selection clipboard...

Is there any reason for that ? No, that's a just bug...

Regards, Pavel

2011/6/6 Pavel Porvatov <pavel.porvatov at oracle.com_ _<mailto:pavel.porvatov at oracle.com>> Hi Sean, Hi,

I reported, but the system doesn't reply me a bug number. It says "will give me email", but I haven't got one yet. Is this the right process, or I might make a problem when reporting? I don't know why the system didn't report bug ID, but your bug was filed successfully. You can find it here: http://bugs.sun.com/bugdatabase/viewbug.do?bugid=7049024 Regards, Pavel

2011/5/27 Pavel Porvatov <pavel.porvatov at oracle.com_ _<mailto:pavel.porvatov at oracle.com>> Hi Sean, Hi all,

I have a testcase related to DnD failure with JTextArea and JTextField on linux. The testcase is as follows: /* * DnDTest.java */ import java.awt.Color; import java.awt.Component; import java.awt.Dimension; import java.awt.FlowLayout; import java.awt.Frame; import java.awt.event.WindowAdapter; import java.awt.event.WindowEvent; import javax.swing.JTextArea; import javax.swing.JTextField;

public class DnDTest extends Frame { Component c; public DnDTest() { super("Single Frame --- AWT Frame"); super.setBackground(Color.gray); // set layout here. setLayout(new FlowLayout()); c = new JTextArea("JTextArea component"); c.setPreferredSize(new Dimension(400, 100)); add(c); c = new JTextField("JTextField component(No IM)"); c.setPreferredSize(new Dimension(400, 20)); add(c); addWindowListener(new WindowAdapter() { public void windowClosing(WindowEvent event) { System.exit(0); } }); setSize(850, 360); setVisible(true); } public static void main(String[] args) { new DnDTest(); } } Reproduce steps: 1. Run the testcase with b143 2. Open a new file with gedit and input some words like "abcde" 3. Drag "abcde" into JTextField and drop it there. 4. Once more, drag "abcde" into JTextField and then move out of the Frame (keep draging) and drag into JTextField again and drop it. Expectation: The second DnD inputs another "abcde" into JTextField. Result: The second DnD inputs nothing into JTextField. Yes, looks like a bug. The test case works on Windows as expected. Investigation: The JTextArea as well has this problem, and in step 4, if we drag "abcde" over JTextField and then drop into JTextArea, nothing is input into JTextArea either. However, if "abcde" is drag into JTextField or JTextArea directly or when JTextArea/Field are empty as in step 2, it works. Are there any comments? And can anyone file a bug for it please ? Anybody can file a bug, http://bugreport.sun.com/bugreport/ Regards, Pavel

-- Best Regards, Sean Chou -- Best Regards, Sean Chou

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