[Development] invokeMethod() with function pointers

[Grégoire Barbier]

Le 16/01/2017 à 10:34, Olivier Goffart a écrit :
> What's the use case for this function? For direct call you better of calling
> the function directly,  and the equivalent of QueuedConnection can be achieved
> with QTimer::singleShot.

Hi.

AFAIK there is no other way to call a method across threads *and wait 
for it result* than QMetaObject::invokeMethod() with 
Qt::BlockingQueuedConnection and Q_RETURN_ARG (apart, of course, making 
the called method thread-safe).

I would personally be happy if (like Benjamin proposes) there were some 
compile time check, IDE symbols following/renaming and no longer need to 
declare such methods as Q_INVOKABLE (or slot).
Therefore IMO methods pointers would be great in 
QMetaObject::invokeMethod() as they are in QObject::connect(). :-)

And maybe lambdas too, if there was a way to choose the thread/eventloop 
in which we want the lambda to be executed (but christmas was a few 
weeks ago, I should not dream ;-)).

Also (I still dream), if there was a way to make invokeMethod() 
automagically choose between a direct call and 
Qt::BlockingQueuedConnection, it would be possible to get rid of this idiom:
     if (QThread::currentThread() == this->thread())
        foo = func();
     else
        QMetaObject::invokeMethod(this, "func",
                  Qt::BlockingQueuedConnection,
                  Q_RETURN_ARG(foo));

Kind of Qt::DirectOrBlockingQueuedConnection.



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Grégoire Barbier :: g à g76r.eu :: +33 6 21 35 73 49