Some thoughts on how "resize to fit" could behave:
  1. Width of Holder is the Max width of the items in the collection, and a new "row" would be created when the total width plus padding of the objects in the row exceeds the width of the widest object.
  2. Have attributes that specify Max items per column and Max items per row. Then if Cols=1 then it behaves like the Column object and if Row=1 then it behaves like a Row object. And it always resizes so that all objects are completely visible.
Stephen