This is in regards to Robert Madonna & my questions, about creating
QCCompositionLayer that contains a transparent background. Both of us
saw some strange artifacts on the screen. I found the answer to my
question, so I thought I would post it here for anyone else. It is
fairly obvious, but I had not realize the problem. My composition did
not have the Clear patch (catagory render). Without it, the animation
does not clear (to the background color), every time through the
animation.
