QT Layouts how to make widgets in horizontal layout navigate down instead of overflowing the window

I now have a QHBoxLayout:

| W  W  W  W  W  W |

      

        
        
        
      

    

I resize smaller:

| W  W  W  W |
<------------>

      

        
        
        
      

    

I want (underline - black space):

| W  W  W  W |
| W  W _ _ _ |

      

        
        
        
      

    

I'm not sure which layout will do this. Does anyone have any idea?

The KDE Settings app does what I'm looking for. I downloaded the code and started searching but haven't found what I want yet.