Re: master e37eb7f: Add support for pixel wheel deltas on NS

[Po Lu <luangruo@yahoo.com>]

Eli Zaretskii <eliz@gnu.org> writes:

> I did mean what happens when the precise scrolling information is
> there.

Thanks, then in that case a 5-element list is always produced.

>> AFAIU (and this may not be a very accurate understanding), if event->arg
>> is a cons, it means it might have line scroll information, and has pixel
>> scroll information.
>> 
>> Otherwise, if it is a number, it has only line information.
>> 
>> Otherwise, if the wheel event is double or triple, `double_click_count'
>> will be included.
>> 
>> And otherwise, only the event name and position will be included.
>
> So I think the manual should describe these possibilities, i.e. that
> every member past POSITION can be present or absent, and if it's
> present, the next one could be present or absent, etc.

Does this look OK to you?  Thanks.

@item (wheel-up @var{position} @var{clicks} @var{lines} @var{pixel-delta})
@itemx (wheel-down @var{position} @var{clicks} @var{lines} @var{pixel-delta})
These kinds of event are generated by moving a mouse wheel.  The
@var{position} element is a mouse position list (@pxref{Click
Events}), specifying the position of the mouse cursor when the event
occurred.

@var{clicks}, if present, is the number of times in quick succession
the wheel has been moved.  @xref{Repeat Events}.  @var{lines}, if
present and not @code{nil}, is the number of screen lines that should
be scrolled.  @var{pixel-delta}, if present, is a pair of the form
@w{@code{(@var{x} . @var{y})}}, where @var{x} and @var{y} are the
number of pixels to scroll by in each axis.

Each parameters after @var{position} may be absent.  Additionally,
@var{lines} may be @code{nil}.