Compositeview: Two views. Big View and Little View. Big View is loaded with
the image of a Cessna going down in flames with the example 'Scribe' event
handler. Little View is the beginnings of a user interface.
So based on a pick - another view is created, populated and an eventhandler
is attached. Very cool.
Now - based on a pick - I want to tear down said view and eventhandler. So I
try some variant of:
>
>osgViewer::View* DoomedView = viewer->getView(ViewIndex);
>// break down the camera as much as possible.
>DoomedView->getCamera()->setAllowEventFocus(false);
>unsigned int DoomedChildren = DoomedView->getCamera()->getNumChildren();
>DoomedView->getCamera()->removeChildren(0,DoomedChildren);
>viewer->removeView(DoomedView);
>
in an event handler of the Little View.
So I follow the process and eventually get to:
CompositeViewer::eventTraversal()
for(ViewEventsMap::iterator veitr = viewEventsMap.begin();
veitr != viewEventsMap.end();
++veitr)
{
View* view = veitr->first;
-->
-->At this point in the execution 'view' is pretty thrashed - probably
referencing the
--> view that no longer there??? There are no event handlers associated with
--> this view. I point this out to build the drama. :)
-->
_eventVisitor->setActionAdapter(view);
for(osgGA::EventQueue::Events::iterator itr = veitr->second.begin();
itr != veitr->second.end();
++itr)
{
osgGA::GUIEventAdapter* event = itr->get();
for(View::EventHandlers::iterator hitr = view->getEventHandlers().begin();
hitr != view->getEventHandlers().end();
++hitr)
-->
--> At this point I try to wave it off: Stop! Stop!. There are no event
handlers!
--> Don't look for a begining and an end to nothing. Please!
--> All in vain . . .
--> Everyone in the audience can see it coming. Everyone in the cast and
crew.
--> The only one ignorant of his/her fate is the hero of the story.
-->
std::list
iterator begin()
{ // return iterator for beginning of mutable sequence
return (iterator(_Nextnode(_Myhead), this));
}
-->
--> Access violation reading address XYZ. There is no _Nextnode of _Myhead.
--> I told the computer to stop but would it listen? Oh no.
--> In my despair I wonder if it would've listened to my warnings about the
white rabbit.
--> Probably not - even with the supporting evidence of all the bones.
-->
Now a clever programmer like myself could simply add a check for this and
skip over the offending check in the CompositeViewer. I could also pour sand
into the gears of a finely crafted clock. I'm not in my 20's anymore, and so I
figured I present my case and let those wiser then myself offer guidance. That
I learned in my 30's. :)
-Steve Schneider
---------------------------------
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