Name: rmT116609 Date: 06/18/2002


FULL PRODUCT VERSION :
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 (SP 4)

A DESCRIPTION OF THE PROBLEM :
JOptionPane needs a new message type, WORKING_MESSAGE, which
is an analog of Motif's XmDIALOG_WORKING dialog type: the
icon would be an hourglass or other indicator of a
background operation in progress, and by default the only
available button on the dialog would be Cancel.

This is especially important because there is no foolproof
way to block input to a window during a lengthy operation,
other than a modal dialog. When a long operation is
executing, and I want to block user input, my choices are to
show a modal dialog, or traverse the component tree and
disable every component. If any components were already
disabled, I need to save their states so I can restore
things later. The modal dialog is by far the best choice.
Using a glassPane is not a viable option, since it doesn't
block keyboard input.

The only real need is for a "working" icon to be supplied by
each look and feel; otherwise, I'm left trying to
anticipate an icon for every look and feel which might be
installed on a system, which is a pretty silly way to
program. I could make do with a single icon, but I lose the
appearance of look and feel integration which the existing
JOptionPane icons do so well (in the Metal, Windows and
Motif look and feels, at least).

I realize there are a few complications which need to be
considered:

- JOptionPane's show methods block their calling thread,
which probably doesn't make sense if the dialog is intended
to indicate an operation in progress. This can be overcome
with some new threads, but a less awkward solution might be
something like JOptionPane.showWorkingDialog(Component
parentComponent, Thread backgroundTask), which would close
the dialog if/when the passed thread completes, returning a
new value like JOptionPane.COMPLETED_OPTION. (It could also
interrupt the passed task if the user activates the Cancel
button or closes the dialog, but premature interruption of a
task is probably better left to the programmer, who can
check for a return value of JOptionPane.CANCEL_OPTION.)

- There is an implied overlap with ProgressMonitor, but many
tasks have no way of knowing how long they will take, so
progress indicators make no sense. An indeterminate
JProgressBar almost solves the problem, except for the need
for a dialog icon.

- I could try to get by with JOptionPane.INFORMATION_MESSAGE
or even JOptionPane.WARNING_MESSAGE, but neither is really
appropriate, as they imply inappropriate conditions and
consequences of user actions: INFORMATION_MESSAGE implies
notification of an event which has already occurred and
completed; WARNING_MESSAGE implies a (potential) problem.
It appears OSF had similar opinions when they provided Motif
with an XmDIALOG_WORKING dialog type.



REPRODUCIBILITY :
This bug can be reproduced always.

CUSTOMER WORKAROUND :
There are numerous hourglass icons available on the web,
often as part of free icon collections.

With some time and dedication, one could come up with icons
which fit the most common look and feels. (I believe the
Java Look and Feel Guidelines discuss how to design a Metal
icon.)

Of course, one could just use JOptionPane.PLAIN_MESSAGE.

In terms of functionality, a workaround requires three threads:

1. The background task.
2. A thread which waits for the background task to finish,
and closes the dialog at that time.
3. A thread which displays the dialog, and when the dialog
is closed, checks if the task thread is still alive, and if
so, signals the task thread that it should abort
(interrupting the task thread is often sufficient, as long
as the task thread is prepared to handle it).
(Review ID: 153654)
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