Sheets and Drawers?

[Richmond Mathewson]

I've just put this in a button:

on mouseUp
  drawer stack "QQQ" at left
end mouseUp

and, the substack "QQQ" pops out of the RIGHT side of the main stack
because there is insufficient screen real-estate on the LEFT.

Beyond putting something in preOpenStack to guarantee the main stack
is positioned so that the drawer pops out of the correct side when it is 
called
there must be a way to prevent this.

The problem can be seen clearly if one considers a screen resolution of 
800 x 600
and a main stack that is 640 x 480 with substacks that are 400 x 300 
that should be
called from either side of the main stack.

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One of the ways round this (apart from moving the main stack everytime
a drawer pops out - which is not satisfactory) would be to SHEET from 
the sides
of the main stack: i.e. the effect would be that of a drawer emerging 
from one
side of the main stack, but over the main stack rather than beside it.