the window manager. Its standard definition is @code{ignore}; since the
frame has already been made visible, Emacs has no work to do.
-@cindex @code{mouse-wheel} event
-@item (mouse-wheel @var{position} @var{delta})
-This kind of event is generated by moving a wheel on a mouse (such as
-the MS Intellimouse). Its effect is typically a kind of scroll or zoom.
-
-The element @var{delta} describes the amount and direction of the wheel
-rotation. Its absolute value is the number of increments by which the
-wheel was rotated. A negative @var{delta} indicates that the wheel was
-rotated backwards, towards the user, and a positive @var{delta}
-indicates that the wheel was rotated forward, away from the user.
+@cindex @code{wheel-up} event
+@cindex @code{wheel-down} event
+@item (wheel-up @var{position})
+@item (wheel-down @var{position})
+This kind of event is generated by moving a wheel on a mouse. Its
+effect is typically a kind of scroll or zoom.
The element @var{position} is a list describing the position of the
event, in the same format as used in a mouse-click event.
-This kind of event is generated only on some kinds of systems.
+This kind of event is generated only on some kinds of systems. On
+other systems, mouse-4 and mouse-5 may be used instead. For portable
+code, the variables @code{mouse-wheel-up-event} and
+@code{mouse-wheel-down-event} defined in @file{mwheel.el} can be used.
@cindex @code{drag-n-drop} event
@item (drag-n-drop @var{position} @var{files})