QDockWidget causes qt to crash

Question

I Have the version of Qt that is built into ubuntu 11.10. And am trying to use a QDockWidget that cannot actually dock (basically, I just want a window that floats. I don't want to just make the view be a top level view because then I would have the OS window bar up there, which I don't want, and if I were to hide it, then the window won't be movable).

So, I basically make a new Qt Gui project, and don't change any of the files, except for the mainwindow.cpp file, which I change to:

#include "mainwindow.h"
#include "ui_mainwindow.h"

#include <QDockWidget>

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    QDockWidget *dockWidget = new QDockWidget(this);
    // Without window management and attached to mainwindow (central widget)
    dockWidget->setFloating( true );
    // resize by frame only - not positional moveable
    dockWidget->setFeatures( QDockWidget::DockWidgetMovable );
    // never dock in mainwindow
    dockWidget->setAllowedAreas( Qt::NoDockWidgetArea );
    // title
    dockWidget->setWindowTitle( "Dock Widget" );
    // add contents. etc etc....
    dockWidget->show();
}

MainWindow::~MainWindow()
{
    delete ui;
}

The problem is that when I go to move the widget, the whole program crashes. I want to know if I am doing something very wrong, or if there is just a bug in qt.

Answer 1

You made the widget floating but not floatable.

dockWidget->setFeatures( QDockWidget::DockWidgetMovable | 
    QDockWidget::DockWidgetFloatable );

And you can also have a movable frameless window, by handling the mouse dragging yourself through mousePressEvent, mouseReleaseEvent and mouseMoveEvent.

---

How to hide the now useless float button

Based on QDockWidget source code, the "float button" is not shown if there is a title bar widget:

 dockWidget->setTitleBarWidget(new QLabel("Dock Widget", dockWidget));

Or since it has a name (which isn't documented), you can hide it explicitly:

 QAbstractButton * floatButton = 
   dockWidget->findChild<QAbstractButton*>("qt_dockwidget_floatbutton");
 if(floatButton) 
     floatButton->hide();