I'm searching for a solution to do File icon overlays (icon badging) (like Dropbox does it on mac) with cocoa on Mac.
Does anyone knows a way to do this?
I've searched the Xcode docs and looked into scpplugins source code which is kind of old carbon code.
Since the Finder was reworked in Snow Leopard, the older Carbon methods will no longer work. The route I've taken to be able to badge icons in Finder involves writing a custom bundle which then needs to be injected into the Finder.
Look into Wolf Rentzsch's mach_inject (https://github.com/rentzsch/mach_star/tree/master/mach_inject) to be able to inject a custom bundle to a Cocoa application.
Use class-dump to be able to get a look into the header files of a Cocoa application (such as the Finder in Snow Leopard and Lion) to get an idea of what you will need to override in your own bundle.