ClipboardManager is a project mainly written in C and OBJECTIVE-C, it's free.
ClipboardManager Sample Application for AutoCAD for Mac with Cocoa ObjectARX
In an attempt to get back up to speed with AutoCAD's ObjectARX API, I thought it would be a fun experience to port the plugin of the month from last year "ClipboardManager" to AutoCAD for Mac.
Still a work in progress...
Copyright (c) 2010 Josh Johnson
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The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
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