Re: ScrollWheel, Xdps and NSEvent modification

[Richard Frith-Macdonald]

On Friday, March 1, 2002, at 07:16 AM, Richard Frith-Macdonald wrote:

> IMO it sounds like some relatively complex changes, breaking the API 
> and (possibly) existing code,
> when all that's needed for scrollwheel support is either -
>
> 1. map scrollwheel delta to mouse pressure and treat scrollwheeel 
> movement as mouse movement.
> or
> 2. add a scrollwheel event, and put the scrollwheel movement in the 
> data1 field of that event.
>
> Option 1 would add scrollwheel support without any change to the event 
> system.
> Option 2 would add one new event type but make no other changes.

I think I prefer option2, as having a new event type for this aids 
clarity.

Option 1 has two problems -

1. It's not obvious to programmers that a scrollwheel produces mouse 
pressure

2. It relates scrollwheel movement to the mouse - which is not IMO a 
good thing.
While the scrollwheel is located on the mouse, it really has little to do
with it - the mouse being a tool for moving around a 2D environment, and 
the
scrollwheel really being quite an artificial add-on, located on the mouse
solely for physical convenience.
This is rather like the steering wheel on a car including the horn ... 
the extra
control is convenient to put there, but has nothing to do with steering.