Well, I know, RTFM. But, I did look – and in the post, I quoted the advice provided in the API documentation. As hinted at in my post, the advice gave little information on the topic. The declaration "NSBoxPrimary = 0" was useful.
The Human Interface Guidelines have good advice on best practices. Maybe I'm a bit dense but I couldn't find any description of the primary and separator box types in the HIG.
I've also Googled for a few hours trying to figure it out with no luck. The search tool in "developer.apple.com" only points to the API doco.
Topic:
UI Frameworks
SubTopic:
AppKit
Tags: