[Interest] How can I subclass a QDockWidget?

[Alex Malyushytskyy]

As far as I understand you need 3 different objects
(it can be instances of appropriate class or its subclass) for pattern to work:

1. QMainWindow ( add dock widget to)
2. QDockWidget
3. QWidget ( widget for setWidget which would be displayed by QDockWidget )

And 3 is missing in
> void QScaffy::addView(View *view)

Hope this helps.

Alex

On Mon, Jul 30, 2012 at 9:03 AM, Rollastre Prostrit <rollastre at gmail.com> wrote:
> Hello list.
>
> I'm in kubuntu 12.04 with Qt 4.8.1.
>
> I have a class called View which is a subclass of QDockWidget. In its
> constructor I do this
>
> View::View(QWidget* parent = NULL)
>      : QDockWidget(MainWindow::Instance())
> {
>      setFeatures(QDockWidget::DockWidgetClosable |
> QDockWidget::DockWidgetMovable);
> }
>
>
>
>
> if I use the following method to add a view to the main window
>
> void QScaffy::addView(View *view)
> {
>      view->setParent(w);
>
>      qDebug() << "adding view " << view->getViewTitle();
>      view->setWindowTitle(view->getViewTitle());
>      w->addDockWidget(Qt::LeftDockWidgetArea, view, Qt::Horizontal); //
> where w is a MainWindow (subclass of QMainWindow)
> }
>
> my question is: what am I doing wrong to get a 'segmentation fault' in
> qdockwidget.cpp:414?
>
> int QDockWidgetLayout::minimumTitleWidth() const
> {
>      QDockWidget *q = qobject_cast<QDockWidget*>(parentWidget());
> <---------------- this returns a QWidget and upon the cast q points to 0x0
>
>      if (QWidget *title = widgetForRole(TitleBar))
>          return pick(verticalTitleBar, title->minimumSizeHint());
>
>      QSize closeSize(0, 0);
>      QSize floatSize(0, 0);
>      if (hasFeature(q, QDockWidget::DockWidgetClosable)) {
> <------------------------------------- Crash HERE
>          if (QLayoutItem *item = item_list[CloseButton])
>              closeSize = item->widget()->sizeHint();
>      }
>      if (hasFeature(q, QDockWidget::DockWidgetFloatable)) {
>          if (QLayoutItem *item = item_list[FloatButton])
>              floatSize = item->widget()->sizeHint();
>      }
>
>      int titleHeight = this->titleHeight();
>
>      int mw = q->style()->pixelMetric(QStyle::PM_DockWidgetTitleMargin,
> 0, q);
>      int fw = q->style()->pixelMetric(QStyle::PM_DockWidgetFrameWidth,
> 0, q);
>
>      return pick(verticalTitleBar, closeSize)
>              + pick(verticalTitleBar, floatSize)
>              + titleHeight + 2*fw + 3*mw;
> }
>
>
>
> However, if my View is just a plain Widget and I manually create a
> QDockWidget like this it works
>
> void QScaffy::addView(QWidget *view)
> {
>      QDockWidget *dock = new QDockWidget(tr("New"), w);
>      dock->setFeatures(QDockWidget::DockWidgetClosable |
>                        QDockWidget::DockWidgetMovable);
>      dock->setWidget(view);
>
>      w->addDockWidget(Qt::LeftDockWidgetArea, dock, Qt::Horizontal);
>
> }
>
>
>
> Do you have any clue what is going on here?
>
> Thanks in advance.
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