[osg-users] event callback after viewer is done

[Riccardo Corsi]

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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