Javafx embedded in swing multithreaded toolkit issue
Anthony Petrov
anthony.petrov at oracle.com
Thu Mar 22 07:00:04 PDT 2012
On 03/22/12 01:31, Pedro Duque Vieira wrote:
> It's a little hard to describe here the various problems I'm having
> because of this multithreaded toolkit issue.
Please note, we're talking here about TWO independent GUI toolkits
running simultaneously, not ONE multi-threaded toolkit. Hence, the
necessity to use runLater()/invokeLater() for synchronization between
the two is the price you pay to have both toolkits work together.
Once your application is migrated to FX entirely, everything will get
eased. In the meantime you have to rely on invokeLater()/runLater() to
get the job done.
--
best regards,
Anthony
>
> I do use invokeLater and runLater, the problem as you mention lies on
> the synchronization between this two contexts.
> Basically you're faced with the same problem as programmers had with the
> multithreaded AWT toolkit, which had to be rewritten to be single
> threaded because of the difficulties this scenario brought to programmers.
>
> Graham Hamilton (former Sun employee) describes this very well on his
> blog post:
>
> /"I believe you can program successfully with multi-threaded GUI
> toolkits if the toolkit is very carefully designed; if the toolkit
> exposes its locking methodology in gory detail; if you are very smart,
> very careful, and have a global understanding of the whole structure of
> the toolkit. If you get one of these things slightly wrong, things will
> mostly work, but you will get occasional hangs (due to deadlocks) or
> glitches (due to races). This multithreaded approach works best for
> people who have been intimately involved in the design of the toolkit. /
>
> /Unfortunately I don't think this set of characteristics scale to
> widespread commercial use. What you tend to end up with is normal smart
> programmers building apps that don't quite work reliably for reasons
> that are not at all obvious. So the authors get very disgruntled and
> frustrated and use bad words on the poor innocent toolkit. (Like me when
> I first started using AWT. Sorry!)"/
>
>
> Best regards,
>
>
> On Wed, Mar 21, 2012 at 7:12 PM, Anthony Petrov
> <anthony.petrov at oracle.com <mailto:anthony.petrov at oracle.com>> wrote:
>
> To rewrite your app completely in FX? :)
>
> Seriously though, could you briefly describe the exact problem that
> you're trying to resolve?
>
> As a general guideline to writing GUI apps, it is always recommended
> to not block the event processing thread under any circumstances.
> Please note that this requirement is true for almost every GUI
> toolkit out there, including native GUI APIs. Both Swing and FX are
> no exceptions. In other words, operations such as invokeAndWait() on
> the event thread should be avoided at all costs.
>
> Indeed, in case of embedding FX scenes into Swing we have two
> unrelated GUI toolkits running at the same app, and as such
> synchronization between the states of components in these two
> toolkits is a challenging task. We, FX developers, do realize this.
> However, there doesn't seem to exist a simple solution for this
> issue. Best advice is to try and use the invokeLater()/runLater()
> kinds of methods only.
>
> --
> best regards,
> Anthony
>
>
> On 3/21/2012 10:58 PM, Pedro Duque Vieira wrote:
>
> Hi Anthony,
>
> Ok, I see.. So is there any solution to this problem?
>
> Thanks,
>
> On Wed, Mar 21, 2012 at 6:55 PM, Anthony Petrov
> <anthony.petrov at oracle.com <mailto:anthony.petrov at oracle.com>
> <mailto:anthony.petrov at oracle.__com
> <mailto:anthony.petrov at oracle.com>>> wrote:
>
> Hi Pedro,
>
> Tooltips and combo-box popups are examples of scenes that use
> top-level windows. Even if the component showing the popup is
> embedded into a JFXPanel, its popups are always top-level
> windows.
>
> --
> best regards,
> Anthony
>
>
> On 3/21/2012 8:51 PM, Pedro Duque Vieira wrote:
>
> ... or couldn't it be a requirement, to have scenes only
> embedded on
> JFXPanel?
>
> On Wed, Mar 21, 2012 at 2:04 PM, Pedro Duque Vieira <
> pedro.duquevieira at gmail.com <mailto:pedro.duquevieira at gmail.com>
> <mailto:pedro.duquevieira at __gmail.com
> <mailto:pedro.duquevieira at gmail.com>>> wrote:
>
> Hi Artem, thanks for the reply.
>
>
> If FX lived on Swing event dispatch thread, all the FX
> top-level windows
>
> (that are not embedded into JFXPanel) would never
> receive any events.
>
> In this scenario (embedding javafx in swing), what
> situations would there
> be on which top level windows aren't embedded into
> JFXPanel?
>
> I think this problem is very important. If things
> continue
> as they are,
> embedding javafx into swing will be virtually
> impossible as
> this blog post
> illustrates:
> http://weblogs.java.net/blog/____kgh/archive/2004/10/____multithreaded_t.html
> <http://weblogs.java.net/blog/__kgh/archive/2004/10/__multithreaded_t.html>
>
> <http://weblogs.java.net/blog/__kgh/archive/2004/10/__multithreaded_t.html
> <http://weblogs.java.net/blog/kgh/archive/2004/10/multithreaded_t.html>>
>
> Cheers,
>
>
> On Wed, Mar 21, 2012 at 9:23 AM, Artem Ananiev
> <artem.ananiev at oracle.com <mailto:artem.ananiev at oracle.com>
> <mailto:artem.ananiev at oracle.__com
> <mailto:artem.ananiev at oracle.com>>>__wrote:
>
>
> On 3/21/2012 6:17 AM, Pedro Duque Vieira wrote:
>
> Hi,
>
> I've been working for a while on a swing app
> that
> has a javafx scene
> embedded on it.
>
> So in this scenario we have two UI threads,
> one for
> the swing part and
> one
> for the javafx scene (the application thread).
> This situation creates a multithreaded ui
> toolkit
> which is basically a
> nightmare for development.
>
> I don't know if this is possible but it I
> think it
> would be best to merge
> the swing and the javafx application thread
> into one
> when on this
> scenario.
>
> In JavaFX/SWT bridge (FXCanvas) we do exactly
> this: FX
> application thread
> is the same as SWT event thread. Unfortunately, in
> JavaFX/Swing case it is
> not possible.
>
> In a few words, Swing event dispatch thread only
> pumps
> Java events. All
> the native events are dispatched on another thread,
> which is called AWT
> toolkit thread. This thread cannot be accessed from
> outside of AWT, it's
> not a part of public API. If FX lived on Swing event
> dispatch thread, all
> the FX top-level windows (that are not embedded into
> JFXPanel) would never
> receive any events.
>
> Thanks,
>
> Artem
>
>
> One other possible solution that comes to my
> mind and
> also a much
>
> simpler
> and quicker one is to add a
> Platform.invokeAndWait(like what exists on
> swing) alongside the Platform.runLater to
> the javafx
> API.
> And each time I want to invoke something on the
> javafx App thread from
> the
> swing ui thread I call invokeAndWait instead of
> runLater. So effectively
> the two UI threads become only one, because
> they are
> not running
> concurrently but sequentially instead.
>
>
> --
> Pedro Duque Vieira
>
>
>
>
>
>
>
> --
> Pedro Duque Vieira
>
>
>
>
> --
> Pedro Duque Vieira
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