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Re: 2 mice -> 2 pointer ?!?

> > From: Dr Andrew C Aitchison <A.C.Aitchison@xxxxxxxxxxxxxxx>
> > Where does the pointer come in ?
> > 
> > I'm not saying that for a flight simulator it isn't useful to have
> > more than one mouse or trackball; I'm all in favour of an X
> > extension for that (I wouldn't be suprised to hear that there
> > already is one) but that is 2 mice, not 2 pointers.

I've been looking at
the X Input Device Extension Library, which is implemented by XFree86
and some other X servers. Is the request for 2 pointers based on page
2, where it says "All extension input devices are treated like the
core X keyboard in determining their location and focus" ?
I think the next line, about explict focus, is your answer.
As I understand it, an application can grab an input device and make
it control anything it wishes.

> maybe I can add some examples:
> I am working on a container terminal simulation (might be  any robotic
> type simulation in that regard...) where I visualize the crane movement
> during waggon loading and unloading movements (4 degrees of freedom:
> along tracks, transverse to tracks, lifting/lowering, rotation about
> z-axis).
> I'm using both a SpaceMouse  _and_  a regular mouse for my user
> interface which already introduces the notion of distint foci:
> Spacemouse for crane interactive movement, 2D-Mouse for viewpoint
> manipulation at the same time.

I can see why you want lots of degrees of freedom, and lots of inputs,
but I don't really see why more of them are "pointers" in the sense I
understand. It may be appropriate to show "cursors" for these independent
actors, but they are application specific.
In this case I think the fact that they are likely to be 3D is significant.
I'm familiar with the idea of a mouse moving cross-hairs to rotate an
object in 3D, but I'm not sure that I'd expect to see the cross-hairs
if I had a track-ball - I'd just move the ball and expect the object
to follow.
Anyway, an application can take a device and draw its own cursor.

I see an X pointer being as much connected with a keyboard as a mouse;
what should the X server do with 2 pointers ? Shouldn't it leave the
control of foci within an app up to that app.

I don't know anything more about XInput, so I'll stop here,
but I hope that I've given you a feeling for why some of us don't understand
the request for more than one pointer as well as more than one mouse ?

Dr. Andrew C. Aitchison		Computer Officer, DPMMS, Cambridge
A.C.Aitchison@xxxxxxxxxxxxxxx	http://www.dpmms.cam.ac.uk/~werdna

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