On Wed, Jul 06, 2011 at 08:47:59PM +0200, Henrik Rydberg wrote: > > > (C) A third, compromise implementation might be to do something like this: > > > (1) When >=2 fingers are on the pad, report 2 MT-B slots, where: > > > (a) slot[0] reports finger 1 > > > (b) slot[1] reports finger 2 > > > (c) Total number of fingers on pad is indicated by EV_KEY/BTN_TOOL_* is set. > > > (2) If 1 finger is removed, the tracking_id for its slot is invalidated; > > > but, the finger that remains stays in its same slot with the > > > same tracking_id. > > > (3) Whenever the number of fingers changes from/to 3 or more > > > fingers, both slots are always invalidated. > > > New tracking_ids are assigned to both slots which contain the > > > two fingers now being reported. > > > (4) No special driver property is required for this, not even "semi-mt". > > > It should be as pure MT-B as we can get (plus BTN_TOOL_* hack). > > I believe there is a strong userspace assumption that BTN_TOOL_* has > no meaning for real MT devices. Rightfully so, IMO. Hence, I think > semi-mt needs to be used here as well. I think we need to adjust userspace to pay attention to BTN_TOOL_* for MT-B too so that if number of slots advertised does not match BTN_TOOL_* capabilities that means that the device does not privide tracking data for all contacts. Luckily this should be backward-compatible (i.e. older userspace will ignore "extended" fingercounts, newer will pay attention to it). > > > > > > > > This is the best option in my opinion. We will present 2 finger position > > data plus extended finger count. > > We never did put all the details of the bounding box coordinates in > writing, so perhaps this is an opportunity to both fix that and extend > usability to the case so described. The only question is whether there > are applications out there which now assume min/max instead of contact > positions. If anyone knows, please speak up. :-) Otherwise, I am very > much for Daniel's case C, with Dmitry's modification. > > In short: Use the semi-MT property, and send two suitable fingers > along with it. Umm... but it is my understanding that 2 fingers will provide real tracking data, not bounding box, so why would we set semi-MT? Maybe we have different notions of what semi-MT property conveys? For me semi-MT indicates that the device provides 2 coordinates for bounding box. However if semi-MT is not set does not mean that the device provides true tracking for all contacts, but only for advertised slots. There still may be additional data transmitted. Thanks. -- Dmitry -- To unsubscribe from this list: send the line "unsubscribe linux-input" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
