Re: [PATCH] hid-ntrig.c Multitouch cleanup and fix

[Rafi Rubin <rafi@seas.upenn.edu>]

On 03/09/2010 06:23 PM, Henrik Rydberg wrote:
> Rafi Rubin wrote:
>>> Single touch should be goverened by one of BTN_TOUCH or ABS_PRESSURE.
>>> BTN_TOOL_DOUBLETAP is a two-finger event.
>>
>> That definitely makes sense to me.  I really don't know why wacom uses
>> double tap there.
>>
>> Is there any harm in letting through the BTN_0 events?  Is the "rdesc"
>> mapping defined by the hardware or hid?
>
> I cannot imagine BTN_0 will do any harm. In synaptics, the BTN_X buttons are
> mapped to multibuttons without clear-cut usage. The button events that carry
> well-defined semantic meaning with regard to touch screens are BTN_TOUCH (any
> finger), BTN_TOOL_FINGER (one finger), BTN_TOOL_PEN (pen), BTN_TOOL_DOUBLETAP
> (two fingers) and BTN_TOOL_TRIPLETAP (three fingers or more).
>
> Henrik
>

Perhaps we should have a general touch device document.

I looked at the evdev code.  And as you say for single touch devices, 
BTN_TOUCH is the bit that matters.  It only broken because I pulled the 
TOUCH <- 0 when I removed BTN_0.

So why does evdev associate BTN_TOOL_FINGER with touchpads (resulting in 
the wrong set of assumptions and a poorly calibrated touch screen)?  I 
suppose that's really a discussion for another list.


For what its worth, onions are tasty.

Rafi