Bounds of draggable component


If you see the attached screenshot (made using the repaint debugger), are the rectangles, which were drawn each time I dragged the thumb, the bounds of the thumb? If so, why?

Now, I defined the bounds to be the size of the whole area, where the component is moved. Actually, I wanted to limit the bounds to the thumb's size, but then, it is not shown. Does this problem depend on the DraggerComponent or do I have to search somewhere else? 

Maybe you wonder, why that is a problem for me, that these areas (coloured rectangles in the screenshot) are defined... If I have many draggable thumbs, then, of course, these areas overlap and it could happen that I can't reach one thumb anymore...

I hope you tell me that I just miss something in the understanding of draggable components... since I have no idea how to solve this problem.