Remove the Margins

[Serenity]

Hi!

I have a problem with removing the margins of my main widget.

For removing the margins, I try to use qt style sheets and have created this:

QWidget {
 
   	background: qlineargradient(x1: 0, y1: 0, x2: 0, y2: 1,
                                           stop: 0 #050505, stop: 1 #202020);
 
    selection-color: black;
    selection-background-color: silver;
    color: white;
    margin: 0px;
 
}

QWidget {

   	background: qlineargradient(x1: 0, y1: 0, x2: 0, y2: 1,
                                           stop: 0 #050505, stop: 1 #202020);

    selection-color: black;
    selection-background-color: silver;
    color: white;
    margin: 0px;

}

To copy to clipboard, switch view to plain text mode 

Then, I create a Widget and want to show it with any margin. So i create a Button and a filled Rectangle, which should be on the top right and should fill complete the right side of my window. The problem is, that I have a black border, that i can't remove.

Have anyone an idea, how I can complete remove the margin?