Alternatively, you could add a way to get the height/width of a user's resolution so developers wishing to create full-screen apps can stop using hacky workarounds.
For example:
winset( src, "chat_label_window", "pos=0,100%" )
( Would place a control( in this case a completely transparent window bearing a transparent label for chat output ) at the bottom left of the screen )
SizeWindow isn't visible, and has the Title & Status bars disabled. SizeLabel covers that entire window with top left/bottom right anchors.
You can then easily set your %s based on those values - taking into account size of the positioned windows.