<Swing Dev> DnD fails with JTextArea and JTextField

[Sean Chou]

Hi Pavel,

    I'm comfortable with moving the checking into
DefaultCaret#updateSystemSelection
method.
    About regression test, I'm not sure how to write, because it contains
user operation. Can you
give me a similar test so I can write one for this bug?

2011/9/13 Pavel Porvatov <pavel.porvatov at oracle.com>

> **
> 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>
>
>  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/view_bug.do?bug_id=7049024
>
> Regards, Pavel
>
>
> 2011/5/27 Pavel Porvatov <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
>
>
>


-- 
Best Regards,
Sean Chou
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