[Qt-interest] How can I get a rotundity-end QProcessBar?

[Kermit Mei]

Hello, I want to make my QProcessBar has rotundity-ends. For example, I
can set stylesheet like this to get such a Button:
background-image: url(:/images/mypic.png);
border:2px groove gray;
border-radius:13px;
padding:2px 4px;

But, as for a QProcessBar, I can't modify the value-bar in it, it is
always a rectangle bar.

How can I change it, then?

Thanks!