[Qt-interest] Using QGraphicsLayouts inside QGraphicsWidgets

[Mihail Naydenov]

----- Original Message ----

> From: Schimkowitsch Robert <Robert.Schimkowitsch at andritz.com>
> To: qt-interest at qt.nokia.com
> Sent: Mon, June 27, 2011 2:03:20 PM
> Subject: Re: [Qt-interest] Using QGraphicsLayouts inside QGraphicsWidgets
> 
> > > In the constructor initialisation list, I initialize my  LinearLayout
> > > member thus:
> > > m_Layout(this)
> 
> >  Surely that won't work. Did you mean this?
> 
> > m_layout( new  QGraphicsLinearLayout( this ) )
> 
> My original intent before giving the  layout a parent was to declare it
> thus:
> QGraphicsLinearLayout  m_Layout;
> 
> Now, I have made it a reference (preferred to a pointer, by our  coding
> standards), and initialize it thus:
> 
> m_Layout(*(new  QGraphicsLinearLayout(this)))
> 
> However, I have not found it explicitly  mentioned in the docs whether a
> parent QGraphicsLayoutItem will destroy all  children on destruction.
> 
> As far as I understood the Qt source, calling  the QGraphicsLinearLayout
> constructor   calls
> setOwnedByLayout(true);
> which, according to the docs:
> "Returns  whether a layout should delete this item in its destructor. If
> its true, then  the layout will delete it. If its false, then it is
> assumed that another  object has the ownership of it, and the layout
> won't delete this  item."
> 
> However, the parent for m_Layout is a QGraphicsWidget (and  therefore a
> QGraphicsLayoutItem), but not a layout.
> What is the behaviour  for this case?
> 
> Going through the destructors of QGraphicsWidget and  QGraphicsLayoutItem
> suggests to me that no-one will delete my m_Layout  reference, and I have
> to do so myself.
> 

I think you think (and digg) too much :)

In general the QGWidget will be the parent of both the items of the layout and 
the layout itself, and delete them both when destroyed.

MihailNaydenov

> 
> Did I overlook  something?
> 
> Kind regards
> 
> Robert  Schimkowitsch
> 
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