Users must be able to cancel accidental triggering of functions on down-events
People with motor disabilities can accidentally trigger touch or mouse events with unwanted results. Activation can occur when someone touches a screen (down-event) or when they remove their finger (up-event). In mouse interaction, activation can occur when pressing (down-event) or when releasing the mouse button (up-event). Authors can reduce the problem of users inadvertently triggering an action by making activation on the up-event. This gives users the opportunity to move their finger or other pointer (e.g. mouse) away from the wrong target once they hit it.