window-full-height-p

window-full-height-p is a compiled Lisp function in `window.el'.

(window-full-height-p &optional WINDOW)

Return t if WINDOW is as high as its containing frame.
More precisely, return t if and only if the total height of
WINDOW equals the total height of the root window of WINDOW's
frame. WINDOW must be a valid window and defaults to the
selected one.