Stack window flashes on resize

[Mark Smith]

Hi, all, I've searched the archives but not found anything that works.

Rev 2.8.1, MacIntel OS X 10.4.10

This is my script (in the script of a 'disclosure triangle' button):

on openup
   put the rect of this stack into tRect
   put item 2 of tRect + 400 into item 4 of tRect
   set the rect of this stack to tRect
end openup

When it executes, the newly revealed part of the window (it's height  
prior to this is 360) flashes white before the bg pattern is applied.

Using 'lock screen' makes no difference, unfortunatley. I also tried  
Scott Rossi's workaround of moving the stack offscreen, resizing and  
then moving it back. This seems to work smoothly about 1 time in 10,  
the other 9 times I see the disappearance and reappearance. Adding  
'lock screen' at various points solved that problem, but somehow re- 
introduces the white flash.

I also tried hiding and showing the stack, but again, that's visible  
unless used with 'lock screen', when the white flash reappears.

Can this be done? If not, it certainly doesn't encourage the use of  
disclosure triangles in non-white-background stacks, which is what  
I'm trying to do, as I'm not that keen on drawers.

Any ideas most welcome,

Mark