<AWT Dev> Problem with modal Dialog

Oleg Sukhodolsky son.two at gmail.com
Tue Feb 17 00:25:24 PST 2009

Hi Artem,

> BTW, do you know why all the component's events are removed from EventQueue
> when it is being disposed?

Well, I do not know for sure, but I think we do this to avoid handling
of events on disposed component.
Because otherwise every handler will have to check state of the
component and do not perform
some operations.  Of course this may not be an issue for current state
of AWT code, but this it could be
a problem in earlier days :)  Also user code may not be prepared for
such situations.

So, the right/short answer is because of unknown/historical reasons
(and because of backward compatibility) :)


On Tue, Feb 17, 2009 at 10:29 AM, Artem Ananiev <Artem.Ananiev at sun.com> wrote:
> Oleg Sukhodolsky wrote:
>> Hi Artem,
>> On Mon, Feb 16, 2009 at 7:15 PM, Artem Ananiev <Artem.Ananiev at sun.com>
>> wrote:
>>> Roman Kennke wrote:
>>>> Hi Artem,
>>>>>>>>> Hrmpf. Seems I cannot. The disclaimer says 'During the initial
>>>>>>>>> rollout
>>>>>>>>> phase, this site will only be accepting and tracking patch
>>>>>>>>> contributions
>>>>>>>>> from developers without push access to the OpenJDK 6 and 7
>>>>>>>>> forests.'
>>>>>>>>> and
>>>>>>>>>  since I _have_ push access, I can't file bug reports. Too bad.
>>>>>>>>> BTW, simply sending this over the EQ is no solution either, because
>>>>>>>>> then
>>>>>>>>> later it will fail to invokeAndWait(). I will think a little more
>>>>>>>>> about
>>>>>>>>> this, or maybe anybody has a quick idea?
>>>>>>>> Just an idea (have not evaluated it carefully):
>>>>>>>> perhaps we should set keepBlockingEDT to false not in
>>>>>>>> hideAndDisposeHandler(),
>>>>>>>> but in WakingRunnable.run() instead.
>>>>>>> I'm looking at this problem at the moment. The problem is the
>>>>>>> instance
>>>>>>> of WakingRunnable is not run on EDT at all - I don't know why.
>>>>>> I know why. It is because the DisposeAction is run _immediately_,
>>>>>> before
>>>>>> the WakingRunnable had a chance. This DisposeAction calls
>>>>>> removeNotify(),
>>>>>> which leads to all events on the EQ that are related to the Dialog
>>>>>> beeing
>>>>>> discarded.
>>>>> Could you, please, point to the place where all the events are
>>>>> discarded?
>>>>> I don't see any.
>>>> In Component.removeNotify(), we call this:
>>>> Toolkit.getEventQueue().removeSourceEvents(this, false);
>>> OK, I see. What a wonderful code...
>>>> which removes all events related to the component. removeNotify() is
>>>> called from inside the DisposeAction.
>>> For this particular case it's enough to add some additional check to
>>> hideAndDisposeHandler:
>>>        if (showAppContext != curAppContext) {
>>>            // Wake up event dispatch thread on which the dialog was
>>>            // initially shown
>>>            SunToolkit.postEvent(showAppContext, wakingEvent);
>>>            showAppContext = null;
>>> +        } else if (EventQueue.isDispatchThread()) {
>>> +            waking.run();
>>>        } else {
>>>            Toolkit.getEventQueue().postEvent(wakingEvent);
>>>        }
>> this change will fix this particular test, but the same problem may
>> exists even when
>> we call hide() not on EDT, it is just a little bit harder to write
>> test for this ;)
> Well, you're right, it's possible to create such test (post 'dispose' to EDT
> and immediately call 'hide' on main), but it is even more artificial case :)
>> What about moving resetting keepBlockingEDT to WakingEvent.run(), or,
>> perhaps, we can simply change
>> target of WakingEvent from a dialog to toolkit.
>> What do you think?
> I'd prefer if hideAndDisposeHandler() can wait for the waking runnable to
> execute on EDT, so the calling thread is unblocked immediately after the
> call to hide() or dispose(). Of course, the case when the dialog is shown on
> EDT should be covered separately.
> Clearing keepBlockingEDT flag in WakingRunnable.run() would lead to several
> waking runnables to be posted to EDT (and only the last one to be really
> dispatched) which looks weird. Making toolkit be the source of the event
> also looks like a workaround, however it's definitely safe and short fix.
> Thanks,
> Artem
> BTW, do you know why all the component's events are removed from EventQueue
> when it is being disposed?
>> Oleg.
>>> Thanks,
>>> Artem
>>>> /Roman

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