Defer a function call in Qt












2















I have a function in Qt 4.8 (windows), which has 3 things to do, like this:



void f()

{

  //1. Do initialization



  //2. Defer g() for next event (on the same thread) so that it may execute after f() is over



  //3. Call h() which is time consuming

}


Now, I am not sure how to implement the 2nd step i.e. how to ensure that g() is called after the call to f() is complete, on the same thread (but on the different stack). I tried using QTimer but if I provide a short time say 10 ms, the function g() is called even when f() has not completed execution. So, relying on timers does not seem to be a reliable idea. Please help, any ideas are much appreciated.






qt qt4







share|improve this question























  • What does this mean on the same thread (but on the different stack)?

    – Alex F
    Jun 18 '14 at 14:01











  • What prevents you to call g() after f() and not g() from f()?

    – vahancho
    Jun 18 '14 at 14:11











  • So, I want g() to be called from the next event stack of message loop which means that instead of calling g() at this time, I just want to post an event in message loop and call that later when current event processing is complete. I hope it clarifies the things.

    – Aarkan
    Jun 18 '14 at 14:32
















2















I have a function in Qt 4.8 (windows), which has 3 things to do, like this:



void f()

{

  //1. Do initialization



  //2. Defer g() for next event (on the same thread) so that it may execute after f() is over



  //3. Call h() which is time consuming

}


Now, I am not sure how to implement the 2nd step i.e. how to ensure that g() is called after the call to f() is complete, on the same thread (but on the different stack). I tried using QTimer but if I provide a short time say 10 ms, the function g() is called even when f() has not completed execution. So, relying on timers does not seem to be a reliable idea. Please help, any ideas are much appreciated.






qt qt4







share|improve this question























  • What does this mean on the same thread (but on the different stack)?

    – Alex F
    Jun 18 '14 at 14:01











  • What prevents you to call g() after f() and not g() from f()?

    – vahancho
    Jun 18 '14 at 14:11











  • So, I want g() to be called from the next event stack of message loop which means that instead of calling g() at this time, I just want to post an event in message loop and call that later when current event processing is complete. I hope it clarifies the things.

    – Aarkan
    Jun 18 '14 at 14:32














2












2








2








I have a function in Qt 4.8 (windows), which has 3 things to do, like this:



void f()

{

  //1. Do initialization



  //2. Defer g() for next event (on the same thread) so that it may execute after f() is over



  //3. Call h() which is time consuming

}


Now, I am not sure how to implement the 2nd step i.e. how to ensure that g() is called after the call to f() is complete, on the same thread (but on the different stack). I tried using QTimer but if I provide a short time say 10 ms, the function g() is called even when f() has not completed execution. So, relying on timers does not seem to be a reliable idea. Please help, any ideas are much appreciated.






qt qt4







share|improve this question














I have a function in Qt 4.8 (windows), which has 3 things to do, like this:



void f()

{

  //1. Do initialization



  //2. Defer g() for next event (on the same thread) so that it may execute after f() is over



  //3. Call h() which is time consuming

}


Now, I am not sure how to implement the 2nd step i.e. how to ensure that g() is called after the call to f() is complete, on the same thread (but on the different stack). I tried using QTimer but if I provide a short time say 10 ms, the function g() is called even when f() has not completed execution. So, relying on timers does not seem to be a reliable idea. Please help, any ideas are much appreciated.






qt qt4




qt qt4






share|improve this question













share|improve this question











share|improve this question




share|improve this question










asked Jun 18 '14 at 13:58









AarkanAarkan

1,45342244




1,45342244













  • What does this mean on the same thread (but on the different stack)?

    – Alex F
    Jun 18 '14 at 14:01











  • What prevents you to call g() after f() and not g() from f()?

    – vahancho
    Jun 18 '14 at 14:11











  • So, I want g() to be called from the next event stack of message loop which means that instead of calling g() at this time, I just want to post an event in message loop and call that later when current event processing is complete. I hope it clarifies the things.

    – Aarkan
    Jun 18 '14 at 14:32



















  • What does this mean on the same thread (but on the different stack)?

    – Alex F
    Jun 18 '14 at 14:01











  • What prevents you to call g() after f() and not g() from f()?

    – vahancho
    Jun 18 '14 at 14:11











  • So, I want g() to be called from the next event stack of message loop which means that instead of calling g() at this time, I just want to post an event in message loop and call that later when current event processing is complete. I hope it clarifies the things.

    – Aarkan
    Jun 18 '14 at 14:32

















What does this mean on the same thread (but on the different stack)?

– Alex F
Jun 18 '14 at 14:01





What does this mean on the same thread (but on the different stack)?

– Alex F
Jun 18 '14 at 14:01













What prevents you to call g() after f() and not g() from f()?

– vahancho
Jun 18 '14 at 14:11





What prevents you to call g() after f() and not g() from f()?

– vahancho
Jun 18 '14 at 14:11













So, I want g() to be called from the next event stack of message loop which means that instead of calling g() at this time, I just want to post an event in message loop and call that later when current event processing is complete. I hope it clarifies the things.

– Aarkan
Jun 18 '14 at 14:32





So, I want g() to be called from the next event stack of message loop which means that instead of calling g() at this time, I just want to post an event in message loop and call that later when current event processing is complete. I hope it clarifies the things.

– Aarkan
Jun 18 '14 at 14:32












2 Answers
2






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oldest

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Make g() a slot or a Q_INVOKABLE. Then use QMetaObject::invokeMethod(this, "g", Qt::QueuedConnection).






share|improve this answer































    0














    If I understand correctly, it's needed simply to call g() after f(), but on the next message loop cycle, after all Qt events issued from f() would be processed. In this case I suggest the following trick:



    f();
    
QApplication::processEvents();
    
g();





    share|improve this answer























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      2 Answers
      2






      active

      oldest

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      2 Answers
      2






      active

      oldest

      votes









      active

      oldest

      votes






      active

      oldest

      votes









      4














      Make g() a slot or a Q_INVOKABLE. Then use QMetaObject::invokeMethod(this, "g", Qt::QueuedConnection).






      share|improve this answer




























        4














        Make g() a slot or a Q_INVOKABLE. Then use QMetaObject::invokeMethod(this, "g", Qt::QueuedConnection).






        share|improve this answer


























          4












          4








          4







          Make g() a slot or a Q_INVOKABLE. Then use QMetaObject::invokeMethod(this, "g", Qt::QueuedConnection).






          share|improve this answer













          Make g() a slot or a Q_INVOKABLE. Then use QMetaObject::invokeMethod(this, "g", Qt::QueuedConnection).







          share|improve this answer












          share|improve this answer



          share|improve this answer










          answered Jun 18 '14 at 18:20









          Kuba OberKuba Ober

          69.7k982186




          69.7k982186

























              0














              If I understand correctly, it's needed simply to call g() after f(), but on the next message loop cycle, after all Qt events issued from f() would be processed. In this case I suggest the following trick:



              f();
              
QApplication::processEvents();
              
g();





              share|improve this answer




























                0














                If I understand correctly, it's needed simply to call g() after f(), but on the next message loop cycle, after all Qt events issued from f() would be processed. In this case I suggest the following trick:



                f();
                
QApplication::processEvents();
                
g();





                share|improve this answer


























                  0












                  0








                  0







                  If I understand correctly, it's needed simply to call g() after f(), but on the next message loop cycle, after all Qt events issued from f() would be processed. In this case I suggest the following trick:



                  f();
                  
QApplication::processEvents();
                  
g();





                  share|improve this answer













                  If I understand correctly, it's needed simply to call g() after f(), but on the next message loop cycle, after all Qt events issued from f() would be processed. In this case I suggest the following trick:



                  f();
                  
QApplication::processEvents();
                  
g();






                  share|improve this answer












                  share|improve this answer



                  share|improve this answer










                  answered Nov 20 '18 at 18:33









                  RedSoftRedSoft

                  111111




                  111111






























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