Detecting size of ScrollView in EditorGUILayout

Hello. I am trying to make a gui list with drag'n'drop features. Drag is begun on the mouse drag event when i detect the mouse is within the list item rectangle. The problem is that this rectangle goes outside of the upper level ScrollView, or worse, still inside it, but over its scroll bar. This makes it impossible for the user to drag the scrollbar, because he will drag my object instead. I don't know how to detect if the scrollbar is there and where exactly, and if the conent is not scrolled away and overlapped by some completely different GUI. Any ideas for the solution?