On 2/3/2009 4:19 PM, Frédéric wrote:
Le 3/2/2009, "Giovanni Bajo" <ra...@develer.com> a écrit:
The trick is that a signal/slot connection across a thread is different
from a normal one: in a normal connection, slots are called immediately,
within the "emit()" call. Instead, in an asynchronous connection, when
the signal is emitted, an event is posted to the main thread (posting
events is thread-safe); then the receiving thread's exec loop will
process the event and call the correct slot.
In this last case, does the call to emit() immediatly return, and the
thread go on with the next instruction, or does it wait until the event
has really called the slot?
Depends on the connection type (which you can manually specify during
the connect() call, or leave the default).
The default (for connections between different threads) is
Qt.QueuedConnection, which means that the emit() call exits immediately.
Otherwise, you can specify Qt.BlockingQueueConnection: the emitting
thread will wait until the receiving thread has found time to process
all the slots. Notice that it's easy to deadlock, if you don't pay
enough attention (and even if you do ;).
--
Giovanni Bajo
Develer S.r.l.
http://www.develer.com
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