I just filed a bug with Apple’s BugReporter (#5644771). I figured I’d post here to save other devs possible headache. The online NSScroller documentation has the method:

- (void)drawArrow:(NSScrollerArrow)arrow highlight:(BOOL)flag

Anyone who has tried to subclass NSScroller knows that this doesn’t work. This is a documentation error. The method should be:

- (void)drawArrow:(NSScrollerArrow)arrow highlightPart:(BOOL)flag