How to avoid repaint on QFrame?

Question

I have a QFrame that is used to paint some rectangles to represent some periods of the day, for example, the period when the user was sleeping.

To do so I overwrite the paintEvent(QPaintEvent *) function and I'm using a QPainter to paint the rectangles.

It is working fine, the problem is that the paintEvent(QPaintEvent *) function is automatically called multiple times by Qt to repaint the QFrame and it is consuming too much CPU. Actually, I just need to repaint a few times (by manually calling the repaint function).

There is some way that I can avoid the QFrame to automatically repaint itself?

Thanks in advance

I'm using Qt 5.3

Answer 1

I finally found the problem. I was setting the style sheet inside the paintEvent function and I think it was being repainted because of that.

I was doing something like this:

MyFrameBar::MyFrameBar(QWidget *parent) : QFrame(parent)
{
    color = QColor(50, 50, 50, 200);
}

void MyFrameBar::paintEvent(QPaintEvent *)
{
    QString style = "border: 1px solid rgba(%1, %2, %3, %4);";
    style = style.arg(color.red()).arg(color.green()).arg(color.blue()).arg(color.alpha());
    setStyleSheet(style);
    ...
}

I just changed the place where I was setting the style sheet and everything is working fine.

The new code looks like this:

MyFrameBar::MyFrameBar(QWidget *parent) : QFrame(parent)
{
    setColor(QColor(50, 50, 50, 200));
}

void MyFrameBar::paintEvent(QPaintEvent *)
{
    ...
}

void MyFrameBar::setColor(const QColor &color)
{
    this->color = color;

    QString style = "border: 1px solid rgba(%1, %2, %3, %4);";
    style = style.arg(color.red()).arg(color.green()).arg(color.blue()).arg(color.alpha());
    setStyleSheet(style);
}