[Qt-interest] QThread Question

[Donal O'Connor]

Hi Sean,

Ok I see but actually looking at the code, there are some instance's where
it is just a regular method and not a slot. Does this mean, when the method
is called, that it is run in the calling thread?

Plus, no where have specified the connection type to be Queued, I'm assuming
direct connection is the default and this results in the slot being called
in the calling thread?

Bit of a mess the code here!

Donal

On Thu, Aug 6, 2009 at 12:00 PM, Sean Harmer <
sean.harmer at maps-technology.com> wrote:

> Hi,
>
> On Thursday 06 Aug 2009 11:43:01 Donal O'Connor wrote:
> > Hi,
> >
> > I've got code here written by somebody else that seems to make use of
> > several threads but I'm quite worried that the processing is not done in
> a
> > different thread like intended.
> >
> > They've created an object derieved from QThread but never implemented the
> > run method so it defaults to the exec() event state when started.
> > Now, they've created slots and these slots by the looks of it does the
> hard
> > work which to the best of my knowledge results them being run in the
> > calling thread.
> >
> > Am I correct in saying, that if you call a method of a QThread object or
> > arrive at a slot due to a Queued connection that the processing done in
> the
> > slot/method
> > is done in the calling thread and not in the actual thread that was
> stared
> > for the QThread object?
> >
> > To the best of my knowledge, the way it should be done, is all the
> > processing done in the run() method but use the methods/slots to change
> > data/state of thread of the thread but using Mutex's since it's the
> calling
> > thread that will be modifying the data and should be mutually exclusive
> > from the run method which reads or writes to this data.
> >
> >
> > Am I correct in what I'm saying here? - Apologies if it's obvious but
> this
> > code I'm looking at is starting to confuse me.
> I think that this approach will run the slots in the worker thread iff:
>
> * The QThread object has thread-affinity with itself. i.e. you have to call
> moveToThread( myThread ) where myThread is your QThread object. If the
> thread
> is not moved to itself, then it still has affinity with the main thread
> since
> that is where it was created. In this situation the slots would be executed
> in
> the main thread.
>
> * You use QueuedConnection or BlockingQueuedConnection types in your
> connect
> calls. If you make all of your connections after the thread object has been
> moved to its own thread then the connect statement should work this out for
> you. The section in the docs called "Signals and Slots Across Threads"
> explains this.
>
> HTH,
>
> Sean
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