[Qt-interest] Is QAbstractItemModel thread safe?

[Ben Swerts]

> On Monday 29 June 2009 22:03:25 Eric Clark wrote:
> > I was just wondering if it is safe to call functions in the
> > QAbstractItemModel class from a thread that is different than the main
> GUI
> > thread?
> 
> The real question is whether you can call functions from
> QAbstractItemModel
> from any thread != QAbstractItemModel::thread() :-)
> 
> And at least from expierience I can say that it is. I have several models
> in
> their own thread and access each of them with two views (naturally in the
> gui-
> thread) and this runs well for hours (in the range of 4-7 days:).
> 
> The docs say that it is at least re-entreant. And I think the
> communication
> with the views is mostly done with signals/slots and these are sent as
> events
> when crossing threads. BTW: You have to do Q_DECLARE_METATYPE( QModelIndex
> )...

And I was just going to reply that it can be safe as long as you don't put a
view on it...

QAbstractItemModel notifies a QAbstractItemView by signals, so that's
thread-safe. The view, however, then queries the model by calling its
flags(), parent(), rowCount(), columnCount(), data(), etc. functions
directly. I don't see how that can be thread-safe. 

Those functions do not change the model of course. So it could remain safe
as long as you never change the model when any view is connected. This also
means editable views are out of the question. 

In summary, I would strongly advise against it. I hope someone proves me
wrong as I could use the functionality too :)

Greets,


	Ben