Triggering of Events by Mouse Pointer Location

You should avoid having events triggered by movements of the mouse pointer over or off a special area. If you must include triggering, you should make it optional.

Some accessibility aids require the mouse pointer to move when information is explored on the screen. For example, a screen review utility may move the mouse to follow words being read, or a user may need to move the mouse to enlarge certain text.

Reliance on a mouse pointer can be a problem if movement of the mouse causes unexpected results. For example, if text appears when the mouse moves over an object and disappears when the mouse moves off of it, the text essentially disappears each time the user tries to read it!

There are two cases where it is acceptable to trigger changes based on mouse pointer movement, because these cases are already understood by accessibility aids and handled appropriately: