dock title bar crash on close

Hi all,
I have a dock widget custom class who use a custom titlebar.
All works fine but when I close the application and one dock is floating, I have a crash.
Without the custom titlebar I have 0 crash, I tried to find but all looks fine to me.
Code :

Code:

---

CDockWidget::CDockWidget( const QString& Title, QWidget* Parent ) :
QDockWidget( Title, Parent )
{
  m_Titlebar = new CTitlebarWidget( this );
  setTitleBarWidget( m_Titlebar );
  installEventFilter( this );
}
 
bool CDockWidget::eventFilter( QObject* watched, QEvent* event )
{
  switch( event->type() )
  {
    case QEvent::WindowTitleChange :
    {
      m_Titlebar->SetTitle( windowTitle() );
      return true;
    }
 
    case QEvent::NonClientAreaMouseButtonDblClick :
    {
      if( isMaximized() )
        showNormal();
      else
        showMaximized();
      return true;
    }
  }
  return false;
}

---

Code:

---

CTitlebarWidget::CTitlebarWidget( QWidget* Parent ) :
QFrame( Parent )
{
  // Set the object name.
  setObjectName( "Titlebar" );
 
  // Connect the dock signal when the floating state change.
  connect( Parent, SIGNAL( topLevelChanged( bool ) ), this, SLOT( ChangeFloatingState( bool ) ) );
 
  // Create the title label.
  m_TitleLabel = new QLabel( Parent->windowTitle() );
  m_TitleLabel->setObjectName( "TitlebarLabel" );
 
  // Minimize button.
  m_MinimizeButton = new QToolButton;
  m_MinimizeButton->setObjectName( "TitlebarMinimizeButton" );
  connect( m_MinimizeButton, SIGNAL( clicked() ), this, SLOT( MinimizeButton() ) );
 
  // Maximize button.
  m_MaximizeButton = new QToolButton;
  m_MaximizeButton->setObjectName( "TitlebarMaximizeButton" );
  connect( m_MaximizeButton, SIGNAL( clicked() ), this, SLOT( ChangeParentMaximizeState() ) );
 
  // Float button.
  m_FloatButton = new QToolButton;
  m_FloatButton->setObjectName( "TitlebarFloatButton" );
  connect( m_FloatButton, SIGNAL( clicked() ), this, SLOT( FloatButton() ) );
 
  // Close button.
  m_CloseButton = new QToolButton;
  m_CloseButton->setObjectName( "TitlebarCloseButton" );
  connect( m_CloseButton, SIGNAL( clicked() ), Parent, SLOT( close() ) );
 
  // Create the control layout.
  QHBoxLayout* ControlLayout = new QHBoxLayout;
  ControlLayout->setMargin( 0 );
  ControlLayout->setSpacing( 0 );
  ControlLayout->addWidget( m_MinimizeButton );
  ControlLayout->addWidget( m_MaximizeButton );
  ControlLayout->addWidget( m_FloatButton );
  ControlLayout->addWidget( m_CloseButton );
 
  // Set the floating state.
  CDockWidget* ParentDock = static_cast< CDockWidget* >( Parent );
  ChangeFloatingState( ParentDock->isFloating() );
 
  // Create the layout.
  QHBoxLayout* Layout = new QHBoxLayout;
  Layout->setMargin( 4 );
  Layout->addWidget( m_TitleLabel );
  Layout->addLayout( ControlLayout );
 
  // Set the layout.
  setLayout( Layout );
}
 
void CTitlebarWidget::SetTitle( const QString& Title )
{
  m_TitleLabel->setText( Title );
}
 
QString CTitlebarWidget::GetTitle() const
{
  return m_TitleLabel->text();
}
 
void CTitlebarWidget::mouseDoubleClickEvent( QMouseEvent* event )
{
  ChangeParentMaximizeState();
}
 
void CTitlebarWidget::mouseMoveEvent( QMouseEvent* event )
{
  // Base class.
  QFrame::mouseMoveEvent( event );
 
  // Check if we move with the left button.
  if( event->buttons() == Qt::MouseButton::LeftButton )
  {
    // Cast the parent.
    CDockWidget* Parent = static_cast< CDockWidget* >( parent() );
 
    // Change parent state.
    if( Parent->isMaximized() )
      Parent->showNormal();
  }
}
 
void CTitlebarWidget::MinimizeButton()
{
  CDockWidget* Parent = static_cast< CDockWidget* >( parent() );
  Parent->setFloating( false );
}
 
void CTitlebarWidget::FloatButton()
{
  CDockWidget* Parent = static_cast< CDockWidget* >( parent() );
  Parent->setFloating( true );
}
 
void CTitlebarWidget::ChangeParentMaximizeState()
{
  // Cast the parent.
  CDockWidget* Parent = static_cast< CDockWidget* >( parent() );
 
  // Change parent state.
  if( Parent->isMaximized() )
    Parent->showNormal();
  else
    Parent->showMaximized();
}
 
void CTitlebarWidget::ChangeFloatingState( bool Floating )
{
  if( Floating )
  {
    m_MinimizeButton->setVisible( true );
    m_MaximizeButton->setVisible( true );
    m_FloatButton->setVisible( false );
  }
  else
  {
    m_MinimizeButton->setVisible( false );
    m_MaximizeButton->setVisible( false );
    m_FloatButton->setVisible( true );
  }
}

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Is it a possible bug of Qt ?
Thanks

What's the stack trace when you get the crash?
Could m_Titlebar be invalid in the even filter?

Cheers,
_

P.S.: instead of installing an event filter on yourself, how about implementing the event() method?
Should be the same result but much cleaner code wise.

you can debug your program with the stacktrace .
A probable reason is violence memory access

Quote:

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Originally Posted by anda_skoa

What's the stack trace when you get the crash?
P.S.: instead of installing an event filter on yourself, how about implementing the event() method?
Should be the same result but much cleaner code wise.

---

Thanks for the tip, I changed to :

Code:

---

bool CDockWidget::event( QEvent* event )
{
  switch( event->type() )
  {
    case QEvent::WindowTitleChange :
    {
      m_Titlebar->SetTitle( windowTitle() );
      return true;
    }
 
    case QEvent::NonClientAreaMouseButtonDblClick :
    {
      if( isMaximized() )
        showNormal();
      else
        showMaximized();
      return true;
    }
  }
  return QDockWidget::event( event );
}

---

I still searching where the crash is from, maybe something missing in the custom QDockWidget.

I have found the crash, it's here :

Code:

---

void CMainEditorWindow::closeEvent( QCloseEvent* event )
{
  DE::CEngine::Shutdown();
  SDL_Quit();
}

---

Apparently it's because I use a QTimer to refresh my central widget who is a 3D render.
When the application close, manager clear data but the render is called who should not.
Is it a way to avoid this problem ? Maybe a way to know the app is closing ?
Here the code of the widget who call the QTimer :

Code:

---

IRenderWidget::IRenderWidget( QWidget* Parent ) :
QWidget( Parent ),
m_Initialized( false ),
m_RenderWindow( NULL )
{
  // Initialize the widget.
  setMinimumSize( 320, 240 );
  setAttribute( Qt::WA_PaintOnScreen );
  setAttribute( Qt::WA_OpaquePaintEvent );
  setAttribute( Qt::WA_NoSystemBackground );
  setFocusPolicy( Qt::StrongFocus );
  setMouseTracking( true );
 
  // Set the timer interval.
  m_Timer.setInterval( static_cast< int >( (1.0f / 60.0f) * 1000.0f ) );
}

---

Thanks

EDIT: I have found a solution, say me if it's the only one possible :

Code:

---

void IRenderWidget::closeEvent( QCloseEvent* event )
{
  disconnect( &m_Timer, SIGNAL( timeout() ), this, SLOT( UpdateOneFrame() ) );
}
 
void CMainEditorWindow::closeEvent( QCloseEvent* event )
{
  centralWidget()->close();
  DE::CEngine::Shutdown();
  SDL_Quit();
}

---

Quote:

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I still searching where the crash is from, maybe something missing in the custom QDockWidget.

---

Learn how to use a debugger. As others have suggested, the stack trace will tell you exactly where the crash occurs.

Edit -- I see our posts crossed... this is what I originally said:

I would not be surprised to find that it is this line:

Code:

---

CDockWidget* Parent = static_cast< CDockWidget* >( parent() );

---

How do you know that parent() returns a CDockWidget? You don't check, you just assume that the static_cast<> returns a pointer to one. QDockWidget might have several layers of widgets between itself and its contents to help with layout (like QFrame, QAbstractScrollArea, and so forth). Better code is:

Code:

---

CDockWidget* pParent = qobject_cast< CDockWidget* >( parent() );
if ( pParent )
{
   // Non-null, so it really is a CDockWidget and it is safe to do something with it
}

---

To answer your other question:

Code:

---

void IRenderWidget::closeEvent( QCloseEvent* event )
{
disconnect( &m_Timer, SIGNAL( timeout() ), this, SLOT( UpdateOneFrame() ) );
}

---

Can't you just call QTimer::stop() instead? "mTimer" looks like it is a member variable in your IRenderWidget class, so it will be disconnected and destroyed when the IRenderWidget instance is destroyed.

Quote:

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Learn how to use a debugger.

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I saw it, but sounded too weird to me, couldn't believe it.

Quote:

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How do you know that parent() returns a CDockWidget?

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Because CTitleBarWidget is always on a CDockWidget, it's the custom titlebar widget.

Quote:

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Can't you just call QTimer::stop() instead? "mTimer" looks like it is a member variable in your IRenderWidget class, so it will be disconnected and destroyed when the IRenderWidget instance is destroyed.

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The problem is this render widget is central widget and if I don't do that I have the crash, I must stop myself ...
Image to show you how it is : http://uppix.com/f-DreamEditor1453839b9d00168cf5.png.
It's weird that I only had crash when floating, but the leak was always there.