Change QGroupBox's content background - c++

Question

I want to change the background of a QGroupBox, however I would like to only change the inside background (the darker shade of gray below each QGroupBox's title) as shown here:
What I currently have is
QGroupBox {
background-color: red;
border: 3px dashed black;
}
which changes the background of the entire QGroupBox like this:
Is there a way in Qt to only change the "interior box" background rather than the whole container? Thank you in advance.

Answer 1

I guess there are 2 QGroupBox'es involved here, since that is not really clear from your post. Or is there a group box and some other inner container widget?
In either case you should be able to use stylesheets like following:
QGroupBox {
background-color: red;
margin-top:1em;
}
QGroupBox QGroupBox {
background-color: green;
}
QGroupBox::title {
subcontrol-origin: padding;
subcontrol-position: left top;
background: transparent;
margin-top: -2.5em;
}
This will give you following result:
You can of course replace the inner group box by an arbitrary widget.

Answer 2

You can do it using "setStyleSheet" function of widgets.
Get the inner group box object. And set the background color using "setStyleSheet" function.
Pseudo Code:
QGroupBox *innerGBox = new QGroupBox();
innerGBox->setStyleSheet("background-color: red");
To know more about setting styles programmatic , refer below link.
http://doc.qt.io/qt-4.8/stylesheet-examples.html

Answer 3

You need to tell Qt a little more about the kind of style you want, specifically the margins. Playing around a little with this code should give you the desired results:
QGroupBox {
background-color: red;
border: 3px dashed black;
margin-top: 1ex; /* leave space at the top for the title */
}
QGroupBox::title {
subcontrol-origin: margin;
padding: 0 3px;
}
Take a look at the Stylesheet examples