title: Qt widgets added at runtime aren't shown
body: <p>I'm trying to put a new customized widget when the user press a button, using layout->addWidget(mywidget) where layout is a QVBoxLayout, but it's not working. </p>
  
  <p>Tried:
  - Passing this to the widget constructor as parent
  - Passing the layout pointer as the parent
  - Passing 0 as the parent
  - The scrollArea pointer where the customized widget should be in as the parent</p>
  
  <p>None works. When layout->addWidget is called in the constructor it works though.</p>