2008/3/4, Adam Davison <[EMAIL PROTECTED]>:
>
> Hi Wesley,
>
> This is more Qt wierdness I think than multi-threading specifically. I
> assume your problem is that QTcpSocket is going to call back to your
> code at some point using slots and signals. This shouldn't be a
> problem because the event loop is running globally throughout the
> whole application. The only thing you do need to be careful of is that
> any of your code which is triggered by those callbacks will probably
> be running inside the event handler which means that if it takes a
> long time you're delaying processing of user interface events and so
> on.
>
> Or if your problem is really something else then I'm sure we can solve
> that too :)
>
What I gather from this page - http://doc.trolltech.com/4.3/threads.html -
is that it's not so simple (I think).
Some quotes from that page:
* *Event driven objects may only be used in a single thread.* Specifically,
this applies to the timer
mechanism<http://doc.trolltech.com/4.3/timers.html>and the network
module <http://doc.trolltech.com/4.3/qtnetwork.html>. For example, you
cannot start a timer or connect a socket in a thread that is not the object's
thread <http://doc.trolltech.com/4.3/qobject.html#thread>.
* An event loop in a thread makes it possible for the thread to use certain
non-GUI Qt classes that require the presence of an event loop (such as
QTimer <http://doc.trolltech.com/4.3/qtimer.html>,
QTcpSocket<http://doc.trolltech.com/4.3/qtcpsocket.html>,
and QProcess <http://doc.trolltech.com/4.3/qprocess.html>).
If I just try and create a (subclassed) QTcpSocket in the constructor of the
EngineShoutcast and call QTcpSocket::connectToHost() I will _never_ receive
the connected() signal because there is no event loop in the thread it is
running in (if I put in some qApp->processEvents() it works around that
problem, but of course that is not clean and doesn't always work)
Furthermore, this happens after the (subclassed) QTcpSocket object is
destroyed:
ASSERT failure in QCoreApplication::sendEvent: "Cannot send events to
objects owned by a different thread. Current thread 839a0b0. Receiver '' (of
type 'QAbstractSocket') was created in thread 8448ab0", file
kernel/qcoreapplication.cpp
It does not happen if I don't call QTcpSocket::connectToHost().
--
Wesley Stessens <[EMAIL PROTECTED]>
Human Knowledge Belongs To The World - Antitrust (2001)
http://wesley.debianbox.be
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