Return equivalent geometry value for FRAME as a cons with car `+'.
A geometry value equivalent to VALUE for FRAME is returned,
where the value is a cons with car `+', not numeric.
TYPE is the car of the original geometry spec (TYPE . VALUE).
It is `top' or `left', depending on which edge VALUE is related to.
VALUE is the cdr of a frame geometry spec: (left/top . VALUE).
If VALUE is a number, then it is converted to a cons value, perhaps
relative to the opposite frame edge from that in the original spec.
FRAME defaults to the selected frame.
Examples (measures in pixels) -
Assuming display height/width=1024, frame height/width=600:
300 inside display edge: 300 => (+ 300)
(+ 300) => (+ 300)
300 inside opposite display edge: (- 300) => (+ 124)
-300 => (+ 124)
300 beyond display edge
(= 724 inside opposite display edge): (+ -300) => (+ -300)
300 beyond display edge
(= 724 inside opposite display edge): (- -300) => (+ 724)
In the 3rd, 4th, and 6th examples, the returned value is relative to
the opposite frame edge from the edge indicated in the input spec.