Qt Signals and slot thread safety

Question

Let\'s say I have a signal change connected to a slot notify. If the change signal is emitted, the notify slot will start executing.

Now what happ

Answer 1

It depends on connection type you specified via calling connect function. The only way when slot will be launched concurrently is if you specified Qt::DirectConnection AND emitting signal in thread different from slot's thread. If you omit connection type, it would be Qt::AutoConnection. In this case if you emit a signal from one thread, and catching it in another one (e.g. in main GUI thread) - Qt will put a slot's call to the message queue and will make all calls sequentially. Read this for further info - http://qt-project.org/doc/qt-4.8/threads-qobject.html#signals-and-slots-across-threads