client_size(Win, Width, Height) will return in variables (Width, Height) the difference between the right-bottom and the left-top corners of the client area of the window Win.
client_pos(Win, X, Y) will return in variables (X, Y) the left-top corner of the client area of the window Win.
Gets the size or the position of the client area of the window Win (Use _ for Win
to point the current window).
win_func(mouse_wheel(Delta, X, Y)):-
draw_point(X-A, Y-B, rgb(255, 0, 0)).
size and position
Look at the example:
Fractals.pro (in folder Programs)