Jerky animation with NSViewAnimation

FROM : Andy Armstrong
DATE : Tue Jul 04 23:08:02 2006

I've got a panel that contains subview half way down the contents of 
which can change depending on selections made elsewhere in the panel. 
The subview can change size as a result of this. I'm using 
NSViewAnimation to transition to the new subview. I tell the 
NSViewAnimation to

Fade the old subview out
Fade the new subview in
Move other views above the subview up or down depending on whether 
the subview is growing or shrinking
Resize the window's frame

The animation works and everything ends up in the right place, but 
the controls above the subview judder vertically - in other words you 
can see the separate components of the animation taking place - first 
the controls are moved in the window and then the window is resized 
which restores their original position relative to the top of the 
window.

Does anyone have experience with doing this kind of the with 
NSViewAnimation? I'm obviously doing something dumb :)

I'll post the code if necessary - but it's slightly involved and I'm 
hoping just the description of the problem will be enough to ring a 
bell with someone. It as if when you opened a Save As... panel and 
then toggled the advanced view button (to the right of the filename) 
that button and the filename box skipped up and down during animation.

Thanks.

--
Andy Armstrong, hexten.net