Qt drawRect in background - c++

Question

I want to paint the background of a slider. I tried this but the color covers up the whole slider. This is in an inherited class of QSlider
void paintEvent(QPaintEvent *e) {
QPainter painter(this);
painter.begin(this);
painter.setBrush(/*not important*/);
// This covers up the control. How do I make it so the color is in
// the background and the control is still visible?
painter.drawRect(rect());
painter.end();
}

Answer 1

To set the background of a widget you could set the style sheet:
theSlider->setStyleSheet("QSlider { background-color: green; }");
The following will set the background of the widget, allowing you to do more:
void paintEvent(QPaintEvent *event) {
QPainter painter;
painter.begin(this);
painter.fillRect(rect(), /* brush, brush style or color */);
painter.end();
// This is very important if you don't want to handle _every_
// detail about painting this particular widget. Without this
// the control would just be red, if that was the brush used,
// for instance.
QSlider::paintEvent(event);
}
And btw. the following two lines of your sample code will yield a warning:
QPainter painter(this);
painter.begin(this);
Namely this one using GCC:
QPainter::begin: A paint device can only be painted by one painter at
a time.
So make sure, as I do in my example, that you either do QPainter painter(this) or painter.begin(this).