[osg-users] GUIEventHandler called twice - possible bug(s)

[Riccardo Corsi]

Hi Robert,
​​
I know there are many things already going on toward OSG 3.6.0,
but if you get a change to take a look to the sample I've sent, it might be
worth considering possible fixes before the new release is out.

Thank you,
Riccardo

On Mon, Aug 29, 2016 at 6:45 PM, Robert Osfield <robert.osfield at gmail.com>
wrote:

> Thanks Riccardo.  I'm currently submerged in refactoring osgParticle,
> once this is completed I'll have a look at the modified
> osgcallback.cpp.
>
> On 29 August 2016 at 16:20, Riccardo Corsi <riccardo.corsi at kairos3d.it>
> wrote:
> > Hi Robert,
> >
> > please find attached a simple example that shows the issues I was trying
> to
> > explain:
> > - launch with no args to see the initial issue
> > - launch with "--crash" to get the crash i ran into when implementing the
> > callback deriving from osg::Callback
> > - launch with "--fix" to see the way I fixed it with the NodeCallback:
> > comments on the run() and operator() methods explain some concerns for
> this
> > solution
> >
> > Hope this clarifies things :)
> > Ricky
> >
> >
> > On Mon, Aug 29, 2016 at 4:29 PM, Robert Osfield <
> robert.osfield at gmail.com>
> > wrote:
> >>
> >> Hi Ricky,
> >>
> >> The changes to Drawable and the knock on effect to the callbacks is an
> >> awkward one - it would be easy if it we could just discard backwards
> >> compatibility, so it's a far from ideal code, but alas you can't
> >> rewrite history once it's happened.
> >>
> >> From your description I don't have a clear idea of what is being
> >> called twice and whether this is a problem.  Could you create a small
> >> example that illustrates the problem, once I can see first hand I can
> >> review the behaviour and decide whether this is acceptable or is an
> >> bug.
> >>
> >> Thanks,
> >> Robert.
> >>
> >> On 29 August 2016 at 15:00, Riccardo Corsi <riccardo.corsi at kairos3d.it>
> >> wrote:
> >> > Hi all,
> >> >
> >> > I report what I believe could be considered a bug, probably introduced
> >> > after
> >> > the promotion of the Drawable class to a node, together with the new
> >> > callback system.
> >> >
> >> > I have a GUIEventHandler derived class installed on a Drawable.
> >> > After some digging I've realized that it's called twice for every
> event
> >> > due
> >> > to the EventVisitor code here:
> >> >
> >> > https://github.com/openscenegraph/OpenSceneGraph/
> blob/master/include/osgGA/EventVisitor#L86
> >> >
> >> > GUIEventHandler happens to derive both from NodeCallback and
> >> > DrawableEventCallback, resulting in it being called twice. I think
> this
> >> > might be considered as a bug if the intended behavior was to keep
> using
> >> > the
> >> > old GUIEventHandler interface the way it was (when attached to the
> >> > viewer
> >> > for instance, it is called only once as expected).
> >> >
> >> > Relate issue:
> >> > I've re-implemented my callback deriving from osg::Callback, but this
> >> > results in a crash as the osg::CallbackObject interface is used even
> if
> >> > the
> >> > cast does not succeed (first if condition)
> >> >
> >> > https://github.com/openscenegraph/OpenSceneGraph/
> blob/master/include/osgGA/EventVisitor#L93
> >> >
> >> > I fixed that by deriving from osg::NodeCallback, but I had to
> >> > reimplement
> >> > the operator() method instead of run(), as the second is not called by
> >> > the
> >> > visitor - that also it's a bit counter-intuitive with respect to the
> >> > osg::Callback class interface.
> >> >
> >> > Ricky
> >> >
> >> >
> >> >
> >> >
> >> >
> >> >
> >> >
> >> > _______________________________________________
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> >> > osg-users at lists.openscenegraph.org
> >> >
> >> > http://lists.openscenegraph.org/listinfo.cgi/osg-users-
> openscenegraph.org
> >> >
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> >
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