[osg-users] event callback after viewer is done

[Riccardo Corsi]

Hi Robert,

I see your point, nevertheless do you think that either:
- having the event callback called with an "about-to-exit" event
- having a custom callback to added and called by the viewer right before
exiting

would be a sensible addition to osg?

Thanks.
ricky



On Wed, Oct 7, 2015 at 10:17 AM, Robert Osfield <robert.osfield at gmail.com>
wrote:

> Hi Ricky,
>
> I don't have any suggestion for an alternate design as I still really know
> enough about ImGui.  My suggestion would be to look closely at the crash
> and why it's happening.
>
> Requiring different calls to be be done in a particular order is not
> unusual but having things crash when one traversal isn't followed by
> another suggests a problem somewhere in the design/implementation.
>
> Robert.
>
> On 7 October 2015 at 08:50, Riccardo Corsi <riccardo.corsi at kairos3d.it>
> wrote:
>
>> Hi Robert,
>>
>> what I'm trying to do is integrating the ImGui framework and render it
>> natively through osg primitives.
>> This gui works in immediate mode, meaning you have to call the code to
>> create your widgets every frame,
>> which is what I do in the custom code in the frame loop (as this changes
>> for every application).
>> All the rest is handled in custom callbacks attached to some nodes.
>>
>> Basically, ImGui needs these things to happen in order at every frame
>> 1. getting inputs (done in the event callback )
>> 2. call to NewFrame() (called on the "FRAME" event, which is the last one
>> received in the event callback)
>> 3. code to create widgets (explicit in the main loop)
>> 4. call to Render() which produces geometries to be rendered by osg (this
>> is done in the update callback)
>>
>> Now, a call to the code that creates widgets (3.) without a proper
>> NewFrame() (2.) causes a crash.
>> When osgViewer is done, I don't get the event callback, and the code
>> which creates the gui crashes.
>>
>> Any suggestion for an alternative design?
>>
>> Thank you,
>> Ricky
>>
>>
>>
>> On Tue, Oct 6, 2015 at 8:56 PM, Robert Osfield <robert.osfield at gmail.com>
>> wrote:
>>
>>> Hi Ricky,
>>>
>>> I don't know what is in your event callback but for exit to cause a
>>> crash it sounds like something is probably not being managed robustly.  As
>>> I know so little I can't provide any specific advice.
>>>
>>> One possibility might be to call viewer.eventTravseral() after the main
>>> rendering loop.  I can't help be feel there is something amiss in the way
>>> your are managing your event callback and it's associated faculties, and
>>> suspect a small redesign could probably resolve the issue.
>>>
>>> Robert.
>>>
>>> On 6 October 2015 at 18:03, Riccardo Corsi <riccardo.corsi at kairos3d.it>
>>> wrote:
>>>
>>>> Hi all,
>>>>
>>>> I have an event callback which needed to be called before some custom
>>>> code I call in the main application loop, something like:
>>>>
>>>> while()
>>>> {
>>>> viewer.eventTraversal();  // << needed callback here
>>>>
>>>> // custom code
>>>> // prepare stuff to be drawn during next frames
>>>>
>>>> viewer.updateTraversal();
>>>> // ...
>>>> }
>>>>
>>>> When the viewer is about to exit, the event callbacks are not called.
>>>> In my case the callback is needed instead,
>>>> not to cause a segfault to the custom code between osg calls.
>>>>
>>>> The obvious solution is to place the callback directly in the main loop,
>>>> but I'd like to avoid that
>>>> (to keep it more "transparent", as it's a kind of framework to be used
>>>> in several applications).
>>>>
>>>> Have you got any suggestion?
>>>> Thank you!
>>>> Ricky
>>>>
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>>>>
>>>
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