Touchpad stylus mode

Zephaniah E. Hull warp at aehallh.com
Sat Mar 17 21:38:11 EDT 2007


On Sat, Mar 17, 2007 at 09:08:30PM -0400, Albert Cahalan wrote:
> Bert Freudenberg and Jim Gettys had the right idea on March 7th.
> It goes something like this:
> 
> a. Mode switches do not move the pointer.

Mode switches themselves do not move the pointer, however the only way
to trigger a GS to PT switch is to put a stylus on the unit, immediately
after switching to PT mode we get coordinate data for the stylus, which
does cause the pointer to move.

> b. On one device (probably the middle), jumps do not move the pointer.

The GS is set in X to be a relative pointer, there are no jumps.

> c. On the other device, jumps move the pointer. There is no acceleration.

Correct, that's already how things work.
> 
> By "jump" of course I mean lifting your finger/stylus and moving
> it to some other location rather than sliding it to that location.

There's an ALPS bug related to that, however we have worked around it in
the kernel driver for now.
> 
> I tend to think that an equal-cost plain touchpad would be a lot
> more reliable and usable though. Putting the buttons on the side
> (replicated on both sides maybe) would have allowed more front-back
> distance and made two-handed use much easier.

Not my department, I'll leave that for someone else.
> 
> There doesn't seem to be a good solution to unintentional mode switches.
> It will be especially bad when accidentally invoking the relative device

The PT to GS mode switch has a 50ms debounce on it, this can be tweaked
if need be.  However keep in mind that the mode switch just doesn't take
that long.

Zephaniah E. Hull.

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