window--resizable-p

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

(window--resizable-p WINDOW DELTA &optional HORIZONTAL IGNORE TRAIL NOUP NODOWN PIXELWISE)

Return t if WINDOW can be resized vertically by DELTA lines.
WINDOW must be a valid window and defaults to the selected one.
For the meaning of the arguments of this function see the
doc-string of `window--resizable'.

Optional argument PIXELWISE non-nil means interpret DELTA as
pixels.