##
win.setExecOnResize()

    function f(w) {
        // execute function when w1 or w2 is resized. w is a pointer to the
        // resized window
    }
    var w1 = new window(...)
    var w2 = new window(...)
    w1.setExecOnResize(f)
    w2.setExecOnResize(f)

Sets the function to be executed when a window is resized. This function as called with one parmeter: the window that triggered the function by resizing.
In mapping windows this function is almost always defined to submit a new request for a map with new mapsize parameters, based on the actual size of the window after resizing (using the window's contentWidth and contentLeft properties).