Messages in this thread |  | | Date | Fri, 15 Nov 1996 15:23:28 -0600 | From | Keith Rohrer <> | Subject | Re: RFC: A generic pointer protocol |
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Alexandre Maret wrote: > I followed the discussion about this "generic" protocol. > It seems there is a lot of talk about non-generic choices > (cf. pressure). Does the packet need to have a fixed length ? > I don't think so. We could have a config struct that can > describe a pointing device capabilities. For example, > a pressurized-pen tablet (!) : > > The config : > name,min value,max value > > { > {"x",0,6000}, > {"y",0,4000}, > {"pressure",0,15} > } > > When the application (which has to be enhanced a bit) start > up, it just look if there is a "pressure" field in the config. > If yes, then the *application* will know that the 3rd field is > the pressure field, and the the value can be between 0 and 15. The application needs to know which parts of the controller map to which field anyway, right? So the protocol should define a standard for what goes where; certain physical inputs may be represented in multiple fields. Presumably for device-independence at the application level, all ranged inputs would be scaled to the same thing.
So, for example, if all the inputs were 32-bit unsigned integers (big, but not too nasty for alphas), you'd have button-down be -1 (i.e. 0xffffffff) and button-up be 0. Then apps checking for clicks could just test for zero, while things which wanted pressure/velocity could test the actual value.
You know, this is all starting to sound like a cross between a mouse protocol and MIDI...
Keith
-- The priests and the friars/Behold me in dread Because I still love you,/My love, and you're dead. ---Dead Can Dance, "I Am Stretched On Your Grave", based on King/S. O'Connor's rewrite of "The Unquiet Grave", trad. Irish folk.
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