Dlang UI - making widget extend to the bounds of the window

[stunaep via Digitalmars-d-learn]

I'm trying to make a gui program with dlangui, but no matter what 
I do, I cannot get widgets to fill the whole window. The window 
is resizable so I cannot just set the widths to static numbers.

No layoutWidth and layoutHeight set:
http://i.imgur.com/UySt30K.png
layoutWidth/Height set to fill (left widget width 300):
http://i.imgur.com/76tMIFz.png

I need these widgets to extend the width of the window because it 
is resizable
http://i.imgur.com/PiL7Y7f.png

You can see this also on DlangUI ML editor:
  fill:
    http://i.imgur.com/t9DsASt.png

  wrap:
    http://i.imgur.com/FoTS69g.png


  arbitrary number:
    http://i.imgur.com/voiYTWZ.png