Bugzilla

It's unclear that how `<area>` is treated within CSS.  However, it's treated as a transparent object at least when a hit-test of pointing device events and `<area>` can be a target of mouse events and pointer events.

When the pointer is moved over the shape of an `<area>`, browsers dispatch `mouseover` and `pointerover` on the `<area>` instead of the `<img>`. Then, when it's moved out from the shape, browsers dispatch `mouseout` and `pointerout`.

However, Chrome and Safari do not dispatch boundary events when the underneath element of the last pointer position becomes another element. This does not make sense because modifying the layout, e.g., modifying the `<img>` size, causes `mouseover` and `pointerover` on the new element anyway.  Therefore, modifying `usemap` attribute of `<img>` and `coord` attribute of `<area>` should be treated as a layout change.