how to abort a function taking to long to process

[john_god]

Back in Dos, when I had a long time consuming function (depending on the user
input data) and I wanted to give the user the change to abort that function so
he could alter the input data without having to wait for the end of calculation,
I would do something like this:

for (i=0;i<Lots_of_calculation && !kbhit() ;i++)
{
    ....
     lots of calculation;
     blablabla...;
     more calculation;
     .....
}

for (i=0;i<Lots_of_calculation && !kbhit() ;i++)
{
    ....
     lots of calculation;
     blablabla...;
     more calculation;
     .....
}

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the kbhit() would terminate the for, if the user pressed a key.

This did not work in the actual Qt, so I tried something like:

for (i=0;i<Lots_of_calculation && flagAbortFunction ;i++)
{
    ....
     lots of calculation;
     blablabla...
     more calculation;     
     .....
}
 
void someClass::keyPressEvent(QKeyEvent *event)
{
        flagAbortFunction = false;
        QMessageBox(this,"title","Show something to see if the function ended and 
         ask user  input data that process more quicly");
}

for (i=0;i<Lots_of_calculation && flagAbortFunction ;i++)
{
    ....
     lots of calculation;
     blablabla...
     more calculation;     
     .....
}
 
void someClass::keyPressEvent(QKeyEvent *event)
{
        flagAbortFunction = false;
        QMessageBox(this,"title","Show something to see if the function ended and 
         ask user  input data that process more quicly");
}

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this code waits about one minute or so after the keypressed , and only then display
the message box, so it's also not working, because doenst end the 'for'. It seems that
the event keypressed is only processed after the function terminate, because the function
displays all the data, without signs of being interrupted.


Any ideas how how can I achieve my goal ???????

[caduel]

During your function no events are processed (unless you call QCoreApplication::processEvents()).

An alternative is to put your function inside a QThread.

[john_god]

Hi Caduel

I try this in the begginning of the function before the for()

QEventLoop loop;
    loop.processEvents(QEventLoop::AllEvents);
    QCoreApplication app;
    app.processEvents(loop);

QEventLoop loop;
    loop.processEvents(QEventLoop::AllEvents);
    QCoreApplication app;
    app.processEvents(loop);

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I have the errors:

D:/qt4examples/Matematica/matriz.cpp:623: error: no matching function for call to `QCoreApplication::QCoreApplication()'
c:/Qt/2009.01/qt/include/QtCore/../../src/corelib/kernel/qcoreapplication.h:72: note: candidates are: QCoreApplication::QCoreApplication(const QCoreApplication&)

Can you help me on this?

[Ginsengelf]

QCoreApplication::processEvents is static. Just add a call to your for loop:

for (i=0;i<Lots_of_calculation && !bAbort ;i++) // set bAbort in keyPressEvent or wherever you like
{
    ....
     lots of calculation;
     QCoreApplication::processEvents (); // <-- new
     blablabla...;
     more calculation;
     .....
}

for (i=0;i<Lots_of_calculation && !bAbort ;i++) // set bAbort in keyPressEvent or wherever you like
{
    ....
     lots of calculation;
     QCoreApplication::processEvents (); // <-- new
     blablabla...;
     more calculation;
     .....
}

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Ginsengelf

[wysota]

Read this article, it might give you some hints:
Keeping the GUI responsive.

[john_god]

Hi
I did has you told Ginsengelf and it works very good.
Wysota, I read your article, and I am sticking with the easy solution, because it suits my needs, this issue is more vast then I supposed. I am still a newbie, I never have used thread's, but I will get there...