Oh yes, I agree, DPI settings should be global accross the system as much as possible and copy buffer should definetly work consistently. Generally it's the application's responsibility to implement the tie in to these platform systems - on the interface level that should preferably not be tied inseparably to any UI code).

To me however, this is on a different architectural level than how the UI itself is inplemented (which, technically, is just motion graphics with hotspots, but psychologically is the most important part for most users).