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:

someElement.scroll(-50)

The closest methods I saw in the documentation were click and send_keys, but neither of those do scrolling. I've also tried sending scrolls to the page via Javascript, e.g. driver.execute_script("scroll(0,-50)") This doesn't seem to do anything though.

How can I do this?

Answer 1

To reproduce/test a mouse wheel, you'll have to emit the mouseover, mousemove and wheel events to the top element with a script injection.

Here's a working example with Google Map:

from selenium import webdriver
from selenium.common.exceptions import WebDriverException

def wheel_element(element, deltaY = 120, offsetX = 0, offsetY = 0):
  error = element._parent.execute_script("""
    var element = arguments[0];
    var deltaY = arguments[1];
    var box = element.getBoundingClientRect();
    var clientX = box.left + (arguments[2] || box.width / 2);
    var clientY = box.top + (arguments[3] || 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";
    """, element, deltaY, offsetX, offsetY)
  if error:
    raise WebDriverException(error)

options = webdriver.ChromeOptions()
options.add_argument("--disable-infobars --disable-extensions --window-size=1366,768")
driver = webdriver.Chrome(chrome_options=options)
driver.get("https://www.google.co.uk/maps")

# get element
elm = driver.find_element_by_css_selector("#scene > div.widget-scene > canvas")

# zoom in with mouse wheel
wheel_element(elm, -120)

# zoom out with mouse wheel
wheel_element(elm, 120)

As an alternative you could send the zoom shortucts which are +/- with Google map:

# get element
elm = driver.find_element_by_css_selector("#scene > div.widget-scene > canvas")

# zoom in with shortcut
elm.send_keys("+")

# zoom out with shortcut
elm.send_keys("-")

Answer 2

On google map, there is a zoom in/out button. You can use it instead of mouse scroll.

//To click on zoom in

driver.find_element_by_id('widget-zoom-in').click()

//To click on zoom out

driver.find_element_by_id('widget-zoom-out').click()

Answer 3

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.