setValue of ScrollBar Don't work at first time

[sergio87]

Hi!

I open an image in a QLabel as a QPixmap. When I opened the image I resize it. Then I "center" the image respect to a particular pixel. "Center" the image is to set value to the ScrollBar. The code is:

imageLabelCandidate = new QLabel();
imageLabelCandidate->setBackgroundRole(QPalette::Base);
imageLabelCandidate->setSizePolicy(QSizePolicy::Ignored, QSizePolicy::Ignored);
imageLabelCandidate->setScaledContents(true);
 
scrollAreaCandidate = new QScrollArea;
scrollAreaCandidate->setBackgroundRole(QPalette::Dark);
scrollAreaCandidate->setWidget(imageLabelCandidate);
 
void MyClass::openImage(string *path){
QString fileName = QString::fromStdString(*path);
	 if (!fileName.isEmpty()) {
		 QImage image(fileName);
		 if (image.isNull()) {
			 cout << "ERROR opening file" << endl;
			 return;
		 }
		 imageLabelCandidate->setPixmap(QPixmap::fromImage(image));
		 imageLabelCandidate->MPixmap(QPixmap::fromImage(image));
		 imageLabelCandidate->adjustSize();
		 scaleCandidateImage(1.3);
		 scrollAreaCandidate->horizontalScrollBar()->setValue(2000);
	 }
 
void MyClass::scaleCandidateImage(double factor)
{
    Q_ASSERT(imageLabelCandidate->pixmap());
    imageLabelCandidate->resize(factor * imageLabelCandidate->pixmap()->size());
}

imageLabelCandidate = new QLabel();
imageLabelCandidate->setBackgroundRole(QPalette::Base);
imageLabelCandidate->setSizePolicy(QSizePolicy::Ignored, QSizePolicy::Ignored);
imageLabelCandidate->setScaledContents(true);

scrollAreaCandidate = new QScrollArea;
scrollAreaCandidate->setBackgroundRole(QPalette::Dark);
scrollAreaCandidate->setWidget(imageLabelCandidate);

void MyClass::openImage(string *path){
QString fileName = QString::fromStdString(*path);
	 if (!fileName.isEmpty()) {
		 QImage image(fileName);
		 if (image.isNull()) {
			 cout << "ERROR opening file" << endl;
			 return;
		 }
		 imageLabelCandidate->setPixmap(QPixmap::fromImage(image));
		 imageLabelCandidate->MPixmap(QPixmap::fromImage(image));
		 imageLabelCandidate->adjustSize();
		 scaleCandidateImage(1.3);
		 scrollAreaCandidate->horizontalScrollBar()->setValue(2000);
	 }

void MyClass::scaleCandidateImage(double factor)
{
    Q_ASSERT(imageLabelCandidate->pixmap());
    imageLabelCandidate->resize(factor * imageLabelCandidate->pixmap()->size());
}

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The problem is that the first time I call "openImage" it don't set the value 2000 to the horizontalScrollBar. The following times it works properly.

Where I make the mistake?

Thanks in advance!!!!!

[Santosh Reddy]

It is not very clear in what sequence you are doing the things

scrollAreaCandidate->horizontalScrollBar()->setValue(2000);

scrollAreaCandidate->horizontalScrollBar()->setValue(2000);

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this should done some were after you load the pixmap into QLabel, and set the QLabel in the scroll area, and then set the scroll bar position

[sergio87]

That's just what I do, no?

I'll explain: The first eight lines of my code are in the constructor of the class. So, it only be executed once. I call al lot of times to "openImage". The first time I do it not work. And not work only the setValue of the scrollBar, because the resize (MyClass::scaleCandidateImage) works allways.

The following times it works properly.

¿Any ideas?

[Santosh Reddy]

Ok, try adding this

scrollAreaCandidate->horizontalScrollBar()->setValue(2000);
scrollAreaCandidate->update(); //Add this

scrollAreaCandidate->horizontalScrollBar()->setValue(2000);
scrollAreaCandidate->update(); //Add this

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[sergio87]

Thanks!!
I had already tested, and didn't works.

I tried:

scrollAreaCandidate->horizontalScrollBar()->update();
scrollAreaCandidate->update();
scrollAreaCandidate->horizontalScrollBar()->repaint();

scrollAreaCandidate->horizontalScrollBar()->update();
scrollAreaCandidate->update();
scrollAreaCandidate->horizontalScrollBar()->repaint();

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But nothing works!!!

[Santosh Reddy]

were in you code you call openImage(), I mean which objects method / slot?
If openImage() is a slot, to which signal is it connected?

[sergio87]

Thanks for reply!

The connexions are very sophisticated. MyClass emits a signal when is clicked a button. I connect this signal with another slot of other class (MainWindow). MainWindow do some operations and generates a string (path). I emit a signal with this string, and the receiver is MyClass:penImage.

At fisrt time, mainWindow emits the signal with a default path. Perhaps the error could be there. But I can't understand why the first time it scale the image properly and not set the value of the scrollBar!

[MarekR22]

try to use: QScrollArea::alignment-prop I think this is what you really want.

[sergio87]

try to use: QScrollArea::alignment-prop I think this is what you really want.

I read that this is to centre (for example) the content. http://lists.trolltech.com/qt4-previ...ad00063-0.html

Maybe my poor english is confusing. My apologies. Anyway, I tried and it didn't work.

I simplified the code to show you. The "2000", actually, is a variable that contains a different value called pointX. Point is calculated every time I load an image, before the setValue. It contain the correct number in each image, but it didn't set the value to the crolBar...

Thank you very much!!