title: Setting padding and margin to 0 doesn´t work
body: <p>It´s just a container and i want to put widgets inside and hide them and show them. I don´t want it to have any margins or paddings, and it will be invisible (no border, no background)</p>
  
  <p>I set the QWidget#container  to margin:0px, padding:0px through a stylesheet.
  And setObjectName("container") to all the widgets that contain.</p>
  
  <p>Nothing happens. But setting a background color works, so it is executed.</p>
  
  <p>In which cases does this happen?
  How to fix this?</p>