On Mon, Dec 30, 2013 at 12:44:21PM +0100, David Herrmann wrote:

Hi

On Mon, Dec 30, 2013 at 12:20 PM, Antonio Ospite
[off-list ref] wrote:

quoted

On Sun, 29 Dec 2013 16:52:09 -0800
Dmitry Torokhov [off-list ref] wrote:

quoted

Hi Antonio,

On Mon, Dec 23, 2013 at 05:17:43PM +0100, Antonio Ospite wrote:

quoted

Model this part of the API after the Sony PlayStation 3 Controller which
exposes independent analog values for each one of the D-Pad buttons.

The PS3 programming API psl1ght also maps the analog D-Pad buttons
individually.

Hmm, even though the hardware is capable of producing independent analog
values does are they really useful? Looking at my PS3 controller I do
not think users will be pressing up/down and left/right dpad buttons at
the same time.

I must agree it's unlikely, while still possible.

quoted

I'd rather keep using ABS_HAT0X/Y unless there is really good reason for
introducing new events.

Having analog D-Pad values reported independently was proposed for these
reasons:

 - it matches _some_ existing hardware closely (that was the main
   reason TBH, to simplify the drivers);

 - it happens to follow what it's being done for D-Pad digital buttons,
   they are also reported independently.

However if some other hardware reported D-Pad axis combined already
then I agree that using something like ABS_HAT0X/Y is safer, I see
decomposing HORIZ/VERT into the separate LEFT/RIGHT and UP/DOWN to be
less intuitive (not harder tho).

Another doubt: David, in the other email you mentioned we could use
ABS_DPAD_HORIZ/VERT, any particular reason to introduce them in place
of ABS_HAT0X/Y?

A "HAT" is an axis on the top of a joystick, nothing else. It seems
troublesome to overload the definition (which we did for many years).
Device-detection based on advertised ABS-bits gets pretty hard if we
reuse ABS-bits for different hardware. The most annoying example of
what happens is accelerometers being misdetected by Xorg as
mouse-input because they reuse ABS_X/Y.

But they are good as joysticks (also ABS_X/ABS_Y). I do not think having
all unique events for all device types is feasible. Can we provide hints
(via properties) to lessen ambiguity, like we do with direct/indirect
pointers for touchscreens/tablets?

Thanks.

-- 
Dmitry