Resizing mainwindow using resizeEvent works very slow

[A Former User]

@kshegunov said:

If you want a "realtime" behavior, then thread the IO!

And ow can I do that?

I have tried calling only the function to calculate (x, y) without calling drawPath() in resizeEvent() something like this

path->calculatedXY(someVector, width, height);

but it gives me Runtime Error and "index out of range" for the vector used in that function.

[kshegunov]

@soloespresso said:

And ow can I do that?

Look here for an introduction.

but it gives me Runtime Error and "index out of range" for the vector used in that function.

See @jsulm's explanation as to why this is happening.
Additionally your for loop is wrong:

for (int i = 0; i < someX.size()-1; i++)  {

this skips the last element in the vector.

Kind regards.

[A Former User]

@jsulm

@jsulm said:

@soloespresso readPosition() does not set someVector!

I have some other functions in between. The readPosition() I posted is to give an idea what readPosition() does which is extract the data and keep them in a vector.

If the change frequency of the file is so low then you should not read it all the time - it's just wasted time. You can use QFileSystemWatcher class to detect changes in this file and then reread it.

OK, I will take a look on that.

[A Former User]

@kshegunov said:

@soloespresso said:

And ow can I do that?

Look here for an introduction.

Ok, I will take a look.

but it gives me Runtime Error and "index out of range" for the vector used in that function.

See @jsulm's explanation as to why this is happening.
Additionally your for loop is wrong:

for (int i = 0; i < someX.size()-1; i++)  {

this skips the last element in the vector.

Kind regards.

Right!!! I didn't see it. Thank you.

[A Former User]

for (int i = 0; i < someX.size()-1; i++)  {

fix this but still Runtime Error and "index out of range".

I will check QFileSystemWatcher and thread after.

[kshegunov]

@soloespresso

fix this but still Runtime Error and "index out of range".

This hasn't anything to do with your error, it was just an observation. As to the assertion (which I'm assuming your code is failing), you should track that in the debugger.

[A Former User]

@kshegunov said:

@soloespresso

fix this but still Runtime Error and "index out of range".

This hasn't anything to do with your error, it was just an observation. As to the assertion (which I'm assuming your code is failing), you should track that in the debugger.

So let me make sure if what I am doing is ok for Qt.
I have drawPath() in QWidget.

void DrawPath::drawPath(QString inFile, QString outFile, float width, float height)
{
    readPosition(inFile);
    calculatedXY(someVector, width, height);
    writePosition(outFile, latLongPointVector);
}

Can I call calculatedXY(someVector, width, height); outside drawPath() in resizeEvent() like this?

void MainWindow::resizeEvent(QResizeEvent *event)
{

    //scaled window size
    scaledWidth = double(event->size().width())/360.0;
    scaledHeight = double(event->size().height())/180.0;

    //QString inFile = ":/input.txt";
    //QString outFile = "output.txt";

    //set label window size
    ui->label->setGeometry(0, 0, 360*scaledWidth, 180*scaledHeight);

    //set draworbit window size
    //path->drawPath(inFile, outFile, scaledWidth, scaledHeight);
    path->calculatedXY(someVector, scaledWidth, scaledHeight);
    path->setGeometry(0, 0, 360*scaledWidth, 180*scaledHeight);
}

[kshegunov]

@soloespresso
No one is preventing you from calling calculatedXY(), but if it's a good design choice really depends what that function actually does.

[A Former User]

@kshegunov said:

@soloespresso
No one is preventing you from calling calculatedXY(), but if it's a good design choice really depends what that function actually does.

Thank you for the confirmation.
Because calling drawPath() will call readPosition(), calculatedXY() and writePosition(), calling calculatedXY() directly will prevent resizeEvent() to reread the text file.

But this give me that Runtime Error and "index out of range" which I will debug later.

Now the problem is how to draw the line? I use paintEvent() to draw a line and the function is called when drawPath() is called.

[jsulm]

"Now the problem is how to draw the line?" - what is the problem with that? When paintEvent() is called you draw the line.

[A Former User]

@jsulm said:

"Now the problem is how to draw the line?" - what is the problem with that? When paintEvent() is called you draw the line.

But then it means paintEvent() is called directly in resizeEvent()?
Is something like the code below possible?

void MainWindow::resizeEvent(QResizeEvent *event)
{

    //scaled window size
    scaledWidth = double(event->size().width())/360.0;
    scaledHeight = double(event->size().height())/180.0;

    //QString inFile = ":/input.txt";
    //QString outFile = "output.txt";

    //set label window size
    ui->label->setGeometry(0, 0, 360*scaledWidth, 180*scaledHeight);

    //set draworbit window size
    //path->drawPath(inFile, outFile, scaledWidth, scaledHeight);
    path->calculatedXY(someVector, scaledWidth, scaledHeight);
    path->paintEvent();
    path->setGeometry(0, 0, 360*scaledWidth, 180*scaledHeight);
}

[jsulm]

No, paintEvent() is called by Qt whenever a repaint is needed.
For example it is called after resizing a widget (as stated in documentation).

[A Former User]

@jsulm ok. sorry for a dumb question. I have tried it before but it didn't work so I wasn't sure if I understand how it works correctly.

So I tried calling the calculatedXY() directly in resizeEvent(), the line is drawn but not scaled when window is maximized. It is scaled only when I call the whole drawPath().

However, even calling directly calculatedXY() in resizeEvent(), the lag persists. Still appx 4 secs delay....

I have tried changing the size of the background img, even removed it, but still get the same result. I have no idea what could be a reason....