A BBC navigation bar component broke depending on the external monitor

Why are you filtering for screen coordinates in the first place? What if the user is using e.g. an alternative input device that doesn't have a screen? The `click` event should be enough indication that the user has tried to activate the menu. Why reinvent the wheel?

> Why are you filtering for screen coordinates in the first place?

FTA:

> The isInvokedByMouse was checking whether the click event was invoked by a mouse or touch pointer – rather than a keyboard – by checking if the screenX or screenY coordinates were a positive number.

They were trying to detect whether it was keyboard or mouse activation, and whoever wrote it assumed that screen coordinates of mouse events would always be positive.