"get coordinates relative to an origin" fails for "wheel.scroll" actions and a "pointer" origin

The problem is that a Wheel input source in the WebDriver classic specification does not have x and y coordinates. But then we run into a problem in get coordinates relative to an origin. Here the x and y properties of the input source need to be used to calculate the target points.

Ideally the current position of the pointer should be used, but given that it is a different input type there is no access to it. On #1409 the proposal was made to add the scroll action to the pointer input type, and that would have allowed us to actually work with the current pointer position.

Right now both start x and start y of a scroll action always refer to 0, 0 which is similar to the viewport origin.

Having scroll as action for a pointer input device would also make it much more simpler to handle in case of multiple pointer input devices.

Read the WebDriver classic specification sections on wheel input sources and “get coordinates relative to an origin,” then trace how a wheel action with a pointer origin determines its start coordinates. Done means reaching a documented normative resolution for the missing x/y behavior, including whether scroll should belong to pointer input.