image shown in Qlabel -> size increases

[szisziszilvi]

Hi,

I have a main window, I've set a gridlayout on it. I placed some QLabels into the grids where I show images using QLabel::setPixmap(). Thnew images should be shown at some user interactions: pushing buttons, clicking on radiobuttons etc. Now I cannot imagine why but the size of the labels get bigger and bigger on each click. The images are loaded in this way:
ui->label_img->setPixmap(myimg.scaled(ui->label_img->width(),ui->label_img->height(),Qt::KeepAspectRatio));

This is what I would like to solve without setting any size fixed. (window should stay "flexible")
http://youtu.be/YgzcuOXF5RI

Szilvi

[ChrisW67]

The pixmap size follows the label. What in your code is changing the size of the label?

[szisziszilvi]

I've changed now the QLabels' sizePolicy to "Ignored" in the in-built Qt Designer. Now it works fine. But why does it increase otherwise?

[ChrisW67]

Do you have a style sheet attached to the label? Does it add a margin or padding? If so, each time you scale the image you add the margin/padding to it size.

This, for example, does not change the size of the label every two seconds:

#include <QtGui>                                                                                                           
#include <QDebug>
 
class MainWindow: public QMainWindow {
    Q_OBJECT
public:
    MainWindow(QWidget *p = 0): QMainWindow(p) {
 
        QWidget *central = new QWidget(this);
        label1 = new QLabel(this);
        image.load("test.png");
        label1->setPixmap(image);
        qDebug() << image.size() << label1->size(); 
        label2 = new QLabel("Label 2", this);
 
        QVBoxLayout *layout = new QVBoxLayout(central);
        layout->addWidget(label1);
        layout->addWidget(label2);
 
        central->setLayout(layout);
        setCentralWidget(central);
 
        connect(&t, SIGNAL(timeout()), SLOT(tick()));
        t.start(2000);
    }
public slots:
    void tick() {
        QPixmap temp = image.scaled(label1->width(), label1->height(), Qt::KeepAspectRatio);
        qDebug() << temp.size() << label1->size(); 
        label1->setPixmap(temp);
    }
private:
    QPixmap image;
    QLabel *label1 ;
    QLabel *label2 ;
    QTimer t;
};
 
int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
 
    MainWindow m;
    m.show();
    return app.exec();
}
#include "main.moc"

#include <QtGui>                                                                                                           
#include <QDebug>

class MainWindow: public QMainWindow {
    Q_OBJECT
public:
    MainWindow(QWidget *p = 0): QMainWindow(p) {
        
        QWidget *central = new QWidget(this);
        label1 = new QLabel(this);
        image.load("test.png");
        label1->setPixmap(image);
        qDebug() << image.size() << label1->size(); 
        label2 = new QLabel("Label 2", this);

        QVBoxLayout *layout = new QVBoxLayout(central);
        layout->addWidget(label1);
        layout->addWidget(label2);

        central->setLayout(layout);
        setCentralWidget(central);

        connect(&t, SIGNAL(timeout()), SLOT(tick()));
        t.start(2000);
    }
public slots:
    void tick() {
        QPixmap temp = image.scaled(label1->width(), label1->height(), Qt::KeepAspectRatio);
        qDebug() << temp.size() << label1->size(); 
        label1->setPixmap(temp);
    }
private:
    QPixmap image;
    QLabel *label1 ;
    QLabel *label2 ;
    QTimer t;
};

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);

    MainWindow m;
    m.show();
    return app.exec();
}
#include "main.moc"

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unless you add:

qApp->setStyleSheet("QLabel { margin: 5px; }");

qApp->setStyleSheet("QLabel { margin: 5px; }");

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in main().