1px gap between button background and frame top edge
Just wondered if anyone can tell me why there is a 1px gap between the top of the button background and the top of the frame, when I'm expecting the button background to fill the whole area (ie it doesn't have any gaps in the image). I would expect the button bacground would be stretched to fill the frame top completely - seems to fill to the L and R and bottom edges ok. Have I missed a setting or this a bug? Or is there an extra 1px edge around the frame top?
A tiny thing but a tiny bit irritating.

