the effective width of a stack?

[Paul Dupuis]

I can across some old code where I an referring to

if (the effective width of stack X > someValue) then

This code produces no errors and works. However, I was just trying to 
look up 'effective width' to see exactly what it was doing in the 
Livecode 9.6.8 Dictionary and struck out!

Under the 'effective' entry in the 9.6.8 Dictionary, 'width' is not 
listed as an inherited property that 'effective' can be used with. Under 
'width' it is not listed. If I look at the entry to the 'stack' object, 
I find 'width' but that just takes me to the entry for 'width'

Am I imagining something, OR is there such a thing as 'effective width' 
and if so, where the heck is it documented?

PS. I thought the width of a stack (or window) vs the effective width 
was teh difference between the inner dimensions of the stack (the card 
size) and the size  of the stack with borders and titlebar (outer 
dimensions). I forget which is which and, again, can not find it 
documented! Also, I thought that contrary to the Dictionary entry to the 
'effective' keyword, you could SET the 'effective width' of a 
stack/window to change the size of the outer dimensions(?)

I'd appreciate any pointers to where effective width or effective height 
of a stack is documented.