Syncronize Threads

[avis_phoenix]

In one thread calculate an approach to one curve, and in certain steps drawing the current curve and continue calculating, I emit a signal when I want draw this curve, I put a debug message to see the process to draw, like this:

Thread::ProcessX()
{
...
   qDebug()<<"Draw";
   emit draw();
   qDebug()<<"Stop";
...
}
77(signal send to DrawProcess() in the interface
Interface::DrawProcess()
{
  qDebug()<<"Now";
  ...
}

Thread::ProcessX()
{
...
   qDebug()<<"Draw";
   emit draw();
   qDebug()<<"Stop";
...
}
77(signal send to DrawProcess() in the interface
Interface::DrawProcess()
{
  qDebug()<<"Now";
  ...
}

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When I run the program, in the terminal i see this:

Draw
Stop
Now
Draw
Stop
Draw
Stop
Draw
Stop
Now
Now
Now

Draw
Stop
Now
Draw
Stop
Draw
Stop
Draw
Stop
Now
Now
Now

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What's up?

Please Help
P.D. Sorry for my bad english

[jacek]

What kind of connection do you use? Is it a queued one?

[avis_phoenix]

I use Siganls/slot with connect, in the thread have a signal and in the interface a slot.

I don't know what kind of connection I used

[jacek]

I don't know what kind of connection I used

So you have used the automatic connection and in this case it should behave as queued connection. This means that the signal will be stored in receiver's event queue until it processes it. If there are other events to process in that queue, signal delivery will be deferred. And this might cause observed behavior.

[avis_phoenix]

Thanks you so much then I will use Qt:irectConnection

[jacek]

then I will use Qt::DirectConnection

This isn't a good idea. With direct connections the code will be executed withing the thread that emits the signal.

Take a look at QWaitCondition.