Return a list of the edge pixel coordinates of WINDOW's text area.
WINDOW must be a live window and defaults to the selected one.
The returned list has the form (LEFT TOP RIGHT BOTTOM), all relative to
(0,0) at the top left corner of the frame's window area.
RIGHT is one more than the rightmost x position of WINDOW's text area.
BOTTOM is one more than the bottommost y position of WINDOW's text area.
The inside edges do not include the space used by WINDOW's scroll bar,
display margins, fringes, header line, and/or mode line.
(fn &optional WINDOW)