QSlider mouse direct jump

Question

Instead of stepping when the user clicks somewhere on the qslider I want to make the slider jump to that position. How can this be implemented ?

Answer 1

The following code is actually a hack, but it works fine without sub-classing QSlider. The only thing you need to do is to connect QSlider valueChanged signal to your container.

Note1: You must set a pageStep > 0 in your slider

Note2: It works only for an horizontal, left-to-right slider (you should change the calculation of "sliderPosUnderMouse" to work with vertical orientation or inverted appearance)

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{

    // ...
    connect(ui->mySlider, SIGNAL(valueChanged(int)),
            this, SLOT(mySliderValueChanged(int)));
   // ...
}


void MainWindow::mySliderValueChanged(int newPos)
{
    // Make slider to follow the mouse directly and not by pageStep steps
    Qt::MouseButtons btns = QApplication::mouseButtons();
    QPoint localMousePos = ui->mySlider->mapFromGlobal(QCursor::pos());
    bool clickOnSlider = (btns & Qt::LeftButton) &&
                         (localMousePos.x() >= 0 && localMousePos.y() >= 0 &&
                          localMousePos.x() < ui->mySlider->size().width() &&
                          localMousePos.y() < ui->mySlider->size().height());
    if (clickOnSlider)
    {
        // Attention! The following works only for Horizontal, Left-to-right sliders
        float posRatio = localMousePos.x() / (float )ui->mySlider->size().width();
        int sliderRange = ui->mySlider->maximum() - ui->mySlider->minimum();
        int sliderPosUnderMouse = ui->mySlider->minimum() + sliderRange * posRatio;
        if (sliderPosUnderMouse != newPos)
        {
            ui->mySlider->setValue(sliderPosUnderMouse);
            return;
        }
    }
    // ...
}