window-scroll-bars

window-scroll-bars is a built-in function in `C source code'.

(window-scroll-bars &optional WINDOW)

Get width and type of scroll bars of window WINDOW.
WINDOW must be a live window and defaults to the selected one.

Value is a list of the form (WIDTH COLUMNS VERTICAL-TYPE HEIGHT LINES
HORIZONTAL-TYPE). If WIDTH or HEIGHT is nil or VERTICAL-TYPE or
HORIZONTAL-TYPE is t, the window is using the frame's corresponding
value.