Re: RFC: A generic pointer protocol

Kenneth Albanowski (
Fri, 15 Nov 1996 06:52:36 -0500 (EST)

On Fri, 15 Nov 1996, . Tethys SYSTEM ADMIN X wrote:

> Why does pressure have to be treated differently? Surely, it's just
> another dimension? If we're trying to develop a generic pointer
> protocol, why make it specific?
> Tet

Because it isn't obvious which dimension (if any) is pressure. On a mouse,
"pressure" is derived from the buttons. On a pressure sensitive tablet,
it's derived from the pen transducer, and thus the "Z" coordinate. If you
imagine a 3-D digitizing device (such exist) that also includes pen
pressure, then it would be the "A" coordinate.

I'm just saying that pressure is distinct enough from all the other
dimensions to deserve being copied into a specific field. Otherwise
programs would need to be littered with code like:

pressure = PointerRec->dimen[2];
else if(PointerStat->a_is_pressure)
pressure = PointerRec->dimen[3];
pressure = PointerRec->buttons ? 255 : 0;

Kenneth Albanowski (, CIS: 70705,126)