====== NSScrollView ======
Primarily this is used by me to load an image file into a custom view in a particular window.  The relationship/order of objects is:
  - NSWindow
  - NSScrollView
  - NSClipView
  - NSView (where the NSImageRep is drawn)

==== Illustration ====
  * for illustration purposes, a custom view will be added to a window in IB
  * NSView will be subclassed to MyView, and the custom view will use the custom class, MyView
  * with MyView selected in IB, Layout -> Make subviews of -> Scroll View
  * MyView is now the documentView of NSClipView and NSScrollView
  * NSClipView is the contentView of NSScrollView
  * to manually scroll, modify the bounds origin of the NSClipView