Synchronize Scrolling of Two (or More) NSScrollViews
You can make two NSScrollViews scroll in concert quite easily because every scrolled pixel is broadcasted to interested parties. In TableFlip, the main table is a NSTableView contained in a NSScrollView. You can view and hide row numbers in TableFlip; but I didn't want to reload the whole table and mess with the table model to insert and remove the first column. Instead, I use a second table view with a single column. The upside of this approach: I can animate hiding the whole scroll view with the row numbers inside easily without affecting the main table.
Scroll NSScrollView Programmatically Without Showing the Scroller Knobs
I am currently working on a typewriter mode text view. Even though this is a very popular trend for a couple of years, I couldn't find any open source component for this feature. I assume those who figure this out keep it a secret. If that is the case, it doesn't make that much sense nowadays anymore since every 3rd note taking app or so has such a feature already.