QScrollArea can not display the corner border with border-radius

1. When I applied this style of border-radius with QScrollArea, I found that it can't display the corner border correctly. The corner disappeared.

QScrollArea {
    border: 1px solid silver;
    border-radius: 10px;
} 

2. And not only for QScrollArea, but I found QTextArea also has the issue. they are all subclass of QAbstractArea.

But for QTextArea, there is a workaround to fix the issue. Explicitly setting a background color for it. Just like the post [link title|https://stackoverflow.com/q/31767162/5777080].

Unfortunately, this method doesn't work for QScrollArea.