Widget of QScrollArea event filter issue

spobit

See the code from qt source:

void QScrollArea::setWidget(QWidget *widget)
{
    Q_D(QScrollArea);
    if (widget == d->widget || !widget)
        return;

    delete d->widget;
    d->widget = 0;
    d->hbar->setValue(0);
    d->vbar->setValue(0);
    if (widget->parentWidget() != d->viewport)
        widget->setParent(d->viewport);
    if (!widget->testAttribute(Qt::WA_Resized))
        widget->resize(widget->sizeHint());
    d->widget = widget;
    d->widget->setAutoFillBackground(true);
    widget->installEventFilter(this);
    d->widgetSize = QSize();
    d->updateScrollBars();
    d->widget->show();

}

When someone uses QScrollArea as container, and maybe change the widget of QScrollArea to other; then, the code widget->installEventFilter(this);, who to break it? there maybe a big issue.

I do it as follow:

widget->removeEventFilter(widget->parent());
widget->removeEventFilter(widget->parent() ? widget->parent()->parent() : nullptr);
widget->setParent(nullptr);

Maybe better way for you!

Andeol

You are worried the eventfilter stays after the contained widget has been changed? But the line
delete d->widget deletes the previously contained widget. And deleting the widget is enough to stop the filter. So I don't think there is an issue with the way QScrollArea::setWidget is coded.

Christian Ehrlicher

And what's you question/ problem here?

Andeol

You are worried the eventfilter stays after the contained widget has been changed? But the line
delete d->widget deletes the previously contained widget. And deleting the widget is enough to stop the filter. So I don't think there is an issue with the way QScrollArea::setWidget is coded.

spobit

@Andeol
Thank you! It`s a important code and I ignored it.

The container is not my coding, but it can`t delete the component, and then recreate it. Maybe needs a interface to take widget, so, I See:

QWidget *QScrollArea::takeWidget()
{
    Q_D(QScrollArea);
    QWidget *w = d->widget;
    d->widget = 0;
    if (w)
        w->setParent(0);
    return w;
}