What happens after closing and before destruction?

[Raccoon29]

Hi all,

I have two related questions to ask:
1) Is it admitted to set the flag Qt::WA_DeleteOnClose for a QWidget, beyond that for the MDI subwindow that contains it?

If the answer to the 1 is "Yes", the second question:
2) What does a QWidget do right after accepting the closeEvent and before its desctruction?
Because right now this function:

void frmarticle::closeEvent(QCloseEvent *event)
{
    if(!maybeSave())  // check for modifies apported
    {
    	event->ignore(); //modifies apported stop the closement
    	return;
    }
 
    viewport->close(Article); //nullifies pointers
    event->accept(); //accepts close event, it is supposed to destroy this widget now, is it?
}
// now quits the closeEvent and the program raise exception, before calling the destructor

void frmarticle::closeEvent(QCloseEvent *event)
{
    if(!maybeSave())  // check for modifies apported
    {
    	event->ignore(); //modifies apported stop the closement
    	return;
    }

    viewport->close(Article); //nullifies pointers
    event->accept(); //accepts close event, it is supposed to destroy this widget now, is it?
}
// now quits the closeEvent and the program raise exception, before calling the destructor

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So, if I would know what it does after close event and before destructor, I could debug it; if you have any other suggestion don't be shy, I accept everything.

[Raccoon29]

No one know where control goes after closing a Widget in a MDI system??

[wysota]

You can use WA_DeleteOnClose for any widget you want. After an event is accepted, the control is returned to the event loop and the widget is most probably scheduled for deletion using deleteLater() (I'm not sure of that, but that's a quite safe thing to assume) and is deleted when the event queue reaches the delayed destruction event.

I'd suggest using a debugger to see what and why crashes. Most probably you either have a null or invalid pointer or you are trying to delete an object inside a slot connected to a signal originating from the object itself.

[Raccoon29]

Thank you, you have just made me find the courage to install the debug environment

Once I have debugged it, I'll post here more informations.
Thank you for the suggestion.

[Raccoon29]

Ok, debug installed and working, from its scan resulted the following (now we'll see how much deep is your Qt knowledge ):

The application after closeEvent and before destruction stopped the run with the message:
ASSERT failure in QList<T>::at: "index out of range", file ../../include/QtCore/../../src/corelib/tools/qlist.h, line 391

What is the verdict?

[wysota]

"after closeEvent" meaning "after closeEvent returns" or "after closeEvent is called"? It'd say your viewport->close(Article) tries to reference some item in some list and fails because the list is smaller than it expects.

[Raccoon29]

"after closeEvent" meaning "after closeEvent returns" or "after closeEvent is called"?

meaning "after closeEvent accepts the event and return", and I remember that the widget closed is a MdiSubWindow with WA_DeleteOnClose that contains frmarticle (inherited from QWidget)

It'd say your viewport->close(Article) tries to reference some item in some list and fails because the list is smaller than it expects.

Yes, I thought it too, but viewport->close(Article); is called to do just this:

void CViewports::close(EViewport win)
{
    switch(win)
    {
        // Article
        case 1:
        {
            if(pArticle) //pointer to frmarticle, not null for sure
            {
                pArticle=NULL;
                wArticle=NULL;
            }
 
            break;
        }
    [...]
}

void CViewports::close(EViewport win)
{
    switch(win)
    {
        // Article
        case 1:
        {
            if(pArticle) //pointer to frmarticle, not null for sure
            {
                pArticle=NULL;
                wArticle=NULL;
            }

            break;
        }
    [...]
}

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Maybe, since the problem seems to be some list, could be the QTableWidget present in frmarticle be involved in the problem, or I'm totally off-road?

[aamer4yu]

The application after closeEvent and before destruction stopped the run with the message:
ASSERT failure in QList<T>::at: "index out of range", file ../../include/QtCore/../../src/corelib/tools/qlist.h, line 391

Try to trace the lists you are using in the application.

[Raccoon29]

Try to trace the lists you are using in the application.

I would do it, but I'm not using QLists at the moment, and noteven objects that inherit from it.

[wysota]

Of course you are. The mdi window keeps a list of its child windows. You are interacting with it when closing a child window. Maybe you simply shouldn't use the attribute. I suggest you take a look at the source code of the mdi framework and see what happens if you close a child window.

[Raccoon29]

Of course you are. The mdi window keeps a list of its child windows. You are interacting with it when closing a child window. Maybe you simply shouldn't use the attribute. I suggest you take a look at the source code of the mdi framework and see what happens if you close a child window.

Yes,yes, you are right, I noticed it but only after the last post, and then I forgot to edit.
Anyway I've given a look a the source like you suggest, but still the problem is in the shadow.
I found the assert that fails, but still I don't understand why; I'm going to break my head for the second time trying to understand how that subwindows list index works

EDIT: I've already tried to cutout the attribute, but the problem persists.