I just started working on a very simple viewport (using cameraViewport) and right at the beggining had a little problem with framing. I wanted to include a large grid (to help with navigation), but I didn’t want to include it in objects considered for framing (since my camera would always zoom all the way out to see entire grid).
I decided to use a simple noFraming tag on my grid object. I have modified camera extension accordingly on line 169:
if getattr(gop, 'computeBounds', None) is not None and 'noFraming' not in gop.tags:
I am not sure if someone else might find this handy, but I thought I might just put it here. 