Will QTimer timeout signal be sent after stop() is called?

Question

I am working on Qt 5.5 / 4.8 now. I worry about whether timeout() signal could be (occasionally）sent after the timer is explicitly stopped by calling stop() on that instance?

I hope the timeout() signal will be sent just between start() and stop() , but is that the truth?

My situation is: the start() and stop() are both called in main thread, and the timeout() signal is connect as directly connection. (I know that queued connection cannot guarantee the above statement.)

Answer 1

Quick answer: no , it won't be called on most of the cases, but there is at least one exception.

A situation when it may be called is if you have used queued connections . Here you may get the associated slots to be called after you've stopped if, for example, the QTimer::timeout signal happens to be emitted before stopping the timer.

In the case above slots are queued (but not necessarily called), so it may happen that you call QTimer::stop before slots are actually invoked.

If you use queued connections you can check for QTimer::isActive() at the beginning of the slot (you'll need some way to access the timer of course, maybe as a member of the class).