Show an indicator icon after a heavy process

[qt_developer]

Hi all,

I want to show an indicator icon before a heavy process. I've used the next code:

void myClass::heavyProcess(QString path)
{
    setCursor(Qt::WaitCursor);
    QApplication::processEvents();
    // heavy process implementation
    setCursor(Qt::ArrowCursor);
}

void myClass::heavyProcess(QString path)
{
    setCursor(Qt::WaitCursor);
    QApplication::processEvents();
    // heavy process implementation
    setCursor(Qt::ArrowCursor);
}

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But the indicator icon does not show. I think that the reason is because the code is synchronous. Therefore I have used this other implementation:

void myClass::start_heavyProcess(QString path)
{
    setCursor(Qt::WaitCursor);
    QApplication::processEvents();
    m_path = path; // I have added a class attribute to comunicate the value to heavyProcess() method. It is very dirty...
    QTimer::singleShot(0, this, SLOT(on_heavyProcess());
}
 
void myClass::on_heavyProcess()
{
    heavyProcess(m_path);
}
 
void myClass::heavyProcess(QString path)
{
    // heavy process implementation
    setCursor(Qt::ArrowCursor);
}

void myClass::start_heavyProcess(QString path)
{
    setCursor(Qt::WaitCursor);
    QApplication::processEvents();
    m_path = path; // I have added a class attribute to comunicate the value to heavyProcess() method. It is very dirty...
    QTimer::singleShot(0, this, SLOT(on_heavyProcess());
}

void myClass::on_heavyProcess()
{
    heavyProcess(m_path);
}

void myClass::heavyProcess(QString path)
{
    // heavy process implementation
    setCursor(Qt::ArrowCursor);
}

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But the indicator icon does not show all the times and the way to pass parameter to the heavyProcess() method is very bad.

How can I improve the code?

Best regards.

[anda_skoa]

Regarding passing the parameter

void myClass::start_heavyProcess(QString path)
{
    //....
 
    QMetaObject::invokeMethod( this, "heavyProcess", Qt::QueuedConnection, Q_ARG( QString, path ) );
}

void myClass::start_heavyProcess(QString path)
{
    //....

    QMetaObject::invokeMethod( this, "heavyProcess", Qt::QueuedConnection, Q_ARG( QString, path ) );
}

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No idea why your cursor doesn't change though
Does it change if you do not execute the heavyProcess method?

Cheers,
_

[qt_developer]

Hi anda_skoa,

I've used QMetaObject::invokeMethod() instead of QTimer::singleShot(). Is it possible to set a time delay like in QTimer::singleShot()?

Yes, if I do not execute the heavyProcess method, the cursor changes.

Best regards.

[anda_skoa]

I've used QMetaObject::invokeMethod() instead of QTimer::singleShot(). Is it possible to set a time delay like in QTimer::singleShot()?

No, it only delays (that is what Qt::QueuedConnection does) the invocation, i.e. like QTimer::singleShot() with 0 timeout.
If you need a different timeout, you will need QTimer.

Yes, if I do not execute the heavyProcess method, the cursor changes.

Interesting. Your attempt of delaying the blocking processing looks correct to me.

Cheers,
_

[qt_developer]

Hi,

I've solved the problem. I've changed the the code in my first attempt and works properly now:

void myClass::heavyProcess(QString path)
{
    QApplication::setOverrideCursor(Qt::WaitCursor);
    QApplication::processEvents();
    // heavy process implementation
    QApplication::restoreOverrideCursor();
}

void myClass::heavyProcess(QString path)
{
    QApplication::setOverrideCursor(Qt::WaitCursor);
    QApplication::processEvents();
    // heavy process implementation
    QApplication::restoreOverrideCursor();
}

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Best regards.