Thanks for the insight guys. Fortunately I've solved my problem by adding a 1 pixel bitmap. going down the rabbit-hole of trying to fix the underlying problem in the Cocoa widget is beyond my skill. Stephen <div class="gmail_quote">On Thu, 4 Dec 2014 at 11:48, Neil Van Dyke <<a href="mailto:neil@neilvandyke.org">neil@neilvandyke.org</a>> wrote: <blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Antony Blakey wrote on 12/03/2014 10:09 PM: > I'm responsible for the Native L&F for VisualWorks Smalltalk (which is entirely synthetic), and it's a big deal for many of our customers. Even on Windows. Very glad to see a VisualWorks person here! (Not everyone knows, but VisualWorks began pushing the envelope of emulating native GUI look&feel starting circa 1990. IIRC, you could be on your Sun workstation, and switch your VW image between different L&Fs quickly -- a list something like Open Look, Motif, MS Windows, MacOS, and the classic Smalltalk-80. VW was already doing this back when even big-name technical workstation apps didn't even try, and just used a look&feel specific to the app on every platform -- AutoCAD, Interleaf, sorta FrameMaker, etc. Of course, as Antony says, native L&F is harder nowadays, especially since users have become very sensitive to the nuances.) Neil V. ____________________ Racket Users list: <a href="http://lists.racket-lang.org/users" target="_blank">http://lists.racket-lang.org/users</a> </blockquote></div>