Mouse scroll wheel with selenium webdriver, on element without scrollbar?

Question

I\'m trying to drive part of a web map akin to Google Maps, where zoom in/out is done by scrolling while moused over. Ideally, I\'d like to be able to do something like this

Answer 1

Florents great answer could be improved a tiny bit would by outsourcing the JS snippet into a separate file and wrap it into the old-style JS module format with readable parameter names.

A file called e.g. simulate_wheel.js with:

/* global arguments */
(function (element, deltaY, offsetX, offsetY) {
    var box = element.getBoundingClientRect();
    var clientX = box.left + (offsetX || box.width / 2);
    var clientY = box.top + (offsetY || box.height / 2);
    var target = element.ownerDocument.elementFromPoint(clientX, clientY);

    for (var e = target; e; e = e.parentElement) {
        if (e === element) {
            target.dispatchEvent(new MouseEvent("mouseover", {
                view: window,
                bubbles: true,
                cancelable: true,
                clientX: clientX,
                clientY: clientY
            }));
            target.dispatchEvent(new MouseEvent("mousemove", {
                view: window,
                bubbles: true,
                cancelable: true,
                clientX: clientX,
                clientY: clientY
            }));
            target.dispatchEvent(new WheelEvent("wheel", {
                view: window,
                bubbles: true,
                cancelable: true,
                clientX: clientX,
                clientY: clientY,
                deltaY: deltaY
            }));
            return "";
        }
    }
    return "Element is not interactable";
}).apply(null, arguments);

Which then can be read and used the following

# Load it using the module loader, the module in this example is called "helper_js"
# Alternatively, simple read functions could be used
import pkgutil
wheel_js = pkgutil.get_data("helper_js", "simulate_wheel.js").decode("utf8")

def simulate_wheel(element, deltaY=120, offsetX=0, offsetY=0):
    error = element._parent.execute_script(wheel_js, element, deltaY, offsetX, offsetY)
    if error:
        raise WebDriverException(error)

This is similar to how it's down inside the Selenium bindings for Python.