An extension for the OSX cocoa class QLPreviewPanel which is used to show and control Apple's Quicklook panel. (10.7+).
The Category provides two new properties to the PreviewPanel to set additional views in the titlebar. (iOS-like)
@property(nonatomic, retain) NSView *leftBarView;
@property(nonatomic, retain) NSView *rightBarView;
also available via cocoapods
The Extension works in any cocoa app, uses no private API and has no dependencies. The code uses method Swizzling and associative storage [shady but cool] to get the runtime to 'integrate' our category and even do it automatically (only drop in the file and you're good to go!)