Re: [PATCH] Input: wacom - Add POINTER and DIRECT device properties

[Chase Douglas <chasedouglas@gmail.com>]

On 09/17/2011 04:21 AM, Henrik Rydberg wrote:
> Hi Jason,
> 
>>>> Take Wacom's Intuos and Graphire series for example, those tablets
>>>> support both styli and mice. For styli, the default is absolute mode;
>>>> while for mice, it is relative. So, only valid property the tablet can
>>>> tell the user-land is: I am a tablet, i.e., not a touchscreen. Clients
>>>> have to check the tool types to set the default mode to relative
>>>> (BTN_TOOL_MOUSE/LENS) or absolute (BTN_TOOL_PEN/AIRBRUSH/RUBBER...).
>>>
>>> And those modes can be determined using the available axes. However,
>>> when all axes are the same, a statement like "I am a tablet" does not
>>> exist. In that case, distinguishing between touchscreen, touchpad and
>>> tablet becomes a question of interpreting the properties. Such a
>>> distinction cannot be achieved using a single bit of information, and
>>> that was never the intention.
>>>
>> It is certainly true that you cannot separate out the different cases
>> with a single bit. The more properties and hints we can expose to
>> userspace the better. However, at the device level, there's only so
>> much information we *can* expose. We know if its a direct input device
>> or not. We don't know if its relative or absolute, since that depends
>> on the tool in use at any given moment.
> 
> It seems the various arguments we have seen in this thread are all
> logical and well founded, but they originate in different assumptions
> about the semantics of POINTER and DIRECT. Such a debate does
> obviously not satisfy everyone.
> 
> The original intention of the properties are these:
> 
> POINTER - The device needs a visual guide in order to be useful. In
> most cirumstances, this is equivalent to not having a screen directly
> beneath the surface.
> 
> DIRECT - The input device is to be used as if it was overlaying a
> sreen. It could be separate from the screen, but the expected behavior
> should be the same.
> 
> From these definitions, it follows that a device could well be both
> POINTER and DIRECT. For instance, a multitouch tablet designed to
> replace the keyboard would fall into this category.

I think these are the clearest definitions I've seen of these
properties. It would be good to get them documented in
Documentation/input. Henrik, would you be able to do this?

-- Chase