API REVIEW request for RT-19783: Provide an option to allow modal windows to be blocking

[Kevin Rushforth]

Thanks, Artem!

Good suggestion, and I will add that to the description, since someone 
may be puzzled by the behavior if we don't.

-- Kevin


Artem Ananiev wrote:
> Hi, Kevin,
>
> On 4/11/2012 6:38 AM, Kevin Rushforth wrote:
>> Sure, I could add something like that to make it more clear. Anything
>> that causes the window to be no longer showing will cause showAndWait()
>> to return, which includes calling hide() or closing the window through
>> window system interaction.
>>
>> I just realized that there is something else I need to add to the
>> documentation: nested calls are permitted, but an "outer" call to
>> showAndWait() will never return until all "inner" calls return. This can
>> happen in the following case:
>>
>> <SOME EVENT HANDLER> {
>> s1.showAndWait(); // blocks until s1 is hidden
>> some instruction after s1 is hidden
>> }
>>
>> ...
>>
>> <SOME OTHER EVENT HANDLER> {
>> s2.showAndWait(); // blocks until s2 is hidden
>> some instruction after s2 is hidden
>> }
>>
>> At this point you have a nested event loop within a nested event loop.
>> If some piece of code calls "s1.hide()" it will not unblock and exit
>> "some instruction after s1 is hidden" until s2 is also closed.
>
> this is exactly the problem we have in AWT/Swing: we don't strictly 
> specify our behavior for nested modal dialogs in our JavaDoc. It's 
> good to see JavaFX specification is (will be) better in this case :)
>
> However, it's not enough, even if we showAndWait s1 only, without s2. 
> Given that s1.hide() can only be called on JavaFX thread, it will 
> likely be in
>
> <SOME YET ANOTHER EVENT HANDLER> {
>     s1.hide/close();
>     some instructions here
> }
>
> These instructions are executed before "some instruction after s1 is 
> hidden", despite s1.hide() has already been called. What's even worse, 
> there may be many code frames in the stack before the last event 
> handler, and all of them should be exited to proceed with the code 
> after s1.showAndWait().
>
> Thanks,
>
> Artem
>
>> -- Kevin
>>
>>
>> Tom Schindl wrote:
>>> What I'm not clear about is what are the circumstances the call 
>>> returns.
>>> Is it only when the user hits the stages close icon, someone calls the
>>> close/hide method, ...?
>>>
>>> Maybe referring to close/hide in the javadoc makes it clear?
>>>
>>> So the revised javadoc could be:
>>>
>>> -- 
>>> Show the stage and wait for it to be closed (through user 
>>> interaction or
>>> by calling {@link #close} or {@link #hide}) before returning to the
>>> caller. This must be called on the FX Application thread. The stage 
>>> must
>>> not already be visible prior to calling this method. This must not be
>>> called on the primary stage.
>>> -- 
>>>
>>>
>>> Tom
>>>
>>>
>>>
>>> Am 10.04.12 22:43, schrieb Kevin Rushforth:
>>>> JIRA: http://javafx-jira.kenai.com/browse/RT-19783
>>>>
>>>> We have had several requests for a way to block the caller while a
>>>> (modal) dialog is shown. The show() method on a Stage is specified to
>>>> return to the caller immediately regardless of the modality of a 
>>>> stage.
>>>> This is a good semantic for many applications, but complicates the 
>>>> logic
>>>> for other applications which don't want to proceed until the dialog is
>>>> dismissed. It is also needed internally to implement an Alert class 
>>>> (see
>>>> RT-12643 <http://javafx-jira.kenai.com/browse/RT-12643> for example).
>>>> Swing dialog, for example, JOptionPane, work by blocking the caller
>>>> until the dialog is dismissed meaning that Swing application 
>>>> programmers
>>>> are already familiar with that model.
>>>>
>>>> Our proposal for JavaFX 2.2 is to add a new method on Stage,
>>>> showAndWait(), which will block the caller until the stage is hidden.
>>>> Note that while this is primarily useful for modal Stages, there is
>>>> nothing in the API that restricts it to such.
>>>>
>>>> The proposed method and javadoc are described in the JIRA
>>>> <http://javafx-jira.kenai.com/browse/RT-19783?focusedCommentId=110277&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-110277>, 
>>>>
>>>>
>>>> but since it is so short, I will also list it here:
>>>>
>>>> /**
>>>> * Show the stage and wait for it to be closed before returning
>>>> to the
>>>> * caller. This must be called on the FX Application thread. The
>>>> stage
>>>> * must not already be visible prior to calling this method. This
>>>> must not
>>>> * be called on the primary stage.
>>>> *
>>>> * @throws IllegalStateException if this method is called on a
>>>> thread
>>>> * other than the JavaFX Application Thread.
>>>> * @throws IllegalStateException if this method is called on the
>>>> * primary stage.
>>>> * @throws IllegalStateException if this stage is already showing.
>>>> */
>>>> public void showAndWait();
>>>>
>>>>
>>>> -- Kevin
>>>>
>>>
>>>