Name: mf23781 Date: 04/23/99


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Problem Description
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The use of modal dialogs in Java for Win32 causes the enabled-state of all other windows in the same thread to be reset to enabled when the dialog is dismissed. Evaluation and Testcase given below.

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Evaluation
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When the modal dialog is shown (the AwtDialog::WmShowModal() method in src\win32\sun\windows\awt_Dialog.cpp) the ModalDisable() method is called, which in turn calls DisableTopLevelsCallback for every window in the current thread (EnumThreadWindows). This disables every window in the thread.

When the modal dialog is dismissed, (the AwtDialog:WmEndModal() method in src\win32\sun\windows\awt_Dialog.cpp) the ModalEnable() method is called, which in turn calls EnableTopLevelsCallback for every window in the current thread (EnumThreadWindows). This enables every window in the thread.

This takes place regardless of the enabled-state of any of the windows in the first place, and the outcome is that all windows are enabled when the dialog is dismissed.

Workaround/Fix could be to store the enabled-state of all windows in the thread in a linked list when the dialog is created, and restore these states when the dialog is dismissed. This depends on the intended workings of modal dialogs.

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Using the Testcase
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Testcase is provided at the bottom of this bug report. Compile the testcase.
Running the testcase creates a frame with three buttons :
   "Create Child" Creates a new identical frame child window whilst disabling the parent
   "Create Modal Dialog" Creates a modal file dialog
   "Dismiss me" Closes the frame window

Create a child window from the main frame window. The parent window now becomes disabled. Continue to create child windows from each subsequent new frame window created. When you have 3 or 4 disabled frame windows, click "Create Modal Dialog" from the active child window. The modal file dialog is modal to all the frame windows in the application. Dismiss the modal file dialog using the "cancel" button, and notice how all the frame windows which were once disabled now become enabled.

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Testcase ChildFrame.java
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import java.awt.event.*;
import java.awt.*;

public class ChildFrame extends Frame implements ActionListener
{

    public static void main(String args[])
    {
        (new ChildFrame(1, null)).setVisible(true);
    }

    Window parent;
    int id;
    Button b,c,d;

    public ChildFrame(int frameNumber, Window myParent)
    {
        super();
        setSize(400,100);

        id = frameNumber;
        parent = myParent;

        setTitle("Frame Number "+id);

        b = new Button("Dismiss me");
        c = new Button("Create Child");
        d = new Button("Create Modal Dialog");

        setLayout(new BorderLayout());
        add("North",c);
        add("Center",d);
        add("South",b);

        b.addActionListener(this);
        c.addActionListener(this);
        d.addActionListener(this);
    }

    public void setVisible(boolean b)
    {
        if (parent != null)
        {
            if (b)
                parent.setEnabled(false);
            else
            {
                parent.setEnabled(true);
                parent.requestFocus();
            }
        }

        super.setVisible(b);
    }

    public void dispose()
    {
        parent.setEnabled(true);
        parent.requestFocus();
        super.dispose();
    }


    public void actionPerformed(ActionEvent evt)
    {
        if (evt.getSource()==c)
        {
            (new ChildFrame(id+1, this)).setVisible(true);
        } else
            if (evt.getSource()==d)
        {
            java.awt.FileDialog md = new java.awt.FileDialog (this);
            md.show();
        } else

            if (evt.getSource()==b)
        {
            if (id == 1) System.exit(0);
            else dispose();
        }
    }
}
(Review ID: 57391)

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