[PATCH 3/4] Implement MT Slots protocol support

[Peter Hutterer]

On Wed, Jun 23, 2010 at 10:04:39AM -0400, Chase Douglas wrote:
> From: Benjamin Tissoires <tissoire at cena.fr>
> 
> The MT Slots protocol sends only the ABS_MT_* values that have changed
> from a previous set of events. We use the ABS_MT_SLOT value as an index
> into an array of MT valuators.
> (see kernel_src/Documentation/input/multi-touch-protocol.txt)
> 
> The "Abs Tracking ID" value can be used to figure out if a touch is down
> or not. If it is != -1, then the touch is down. Otherwise, the touch is
> up and the other values in the "slot" of valuators are invalid.
> 
> Signed-off-by: Benjamin Tissoires <tissoire at cena.fr>
> Signed-off-by: Chase Douglas <chase.douglas at canonical.com>
> ---
>  src/evdev.c |   34 ++++++++++++++++++++++++++++++++--
>  src/evdev.h |    1 +
>  2 files changed, 33 insertions(+), 2 deletions(-)
> 
> diff --git a/src/evdev.c b/src/evdev.c
> index 68d8946..777eebe 100644
> --- a/src/evdev.c
> +++ b/src/evdev.c
> @@ -527,6 +527,12 @@ EvdevProcessRelativeMotionEvent(InputInfoPtr pInfo, struct input_event *ev)
>      }
>  }
>  
> +static inline BOOL
> +EvdevIsMTEvent(struct input_event *ev)
> +{
> +    return ev->code >= EVDEV_FIRST_MT_AXIS && ev->code <= EVDEV_LAST_MT_AXIS;
> +}
> +

I'd say leave the inlining up to the compiler.
Also, I prefer () around conditions like this for optical navigation but
that's personal preference.

>  /**
>   * Take the absolute motion input event and process it accordingly.
>   */
> @@ -549,7 +555,18 @@ EvdevProcessAbsoluteMotionEvent(InputInfoPtr pInfo, struct input_event *ev)
>      if (EvdevWheelEmuFilterMotion(pInfo, ev))
>          return;
>  
> -    pEvdev->vals[pEvdev->axis_map[ev->code]] = value;
> +    if (!EvdevIsMTEvent(ev) && ev->code != ABS_MT_SLOT)
> +        pEvdev->vals[pEvdev->axis_map[ev->code]] = value;
> +    else if (ev->code == ABS_MT_SLOT) {

please swap this condition with the first one so you can skip the !=
ABS_MT_SLOT. Makes for better readability.

> +        pEvdev->mt_current_touchpoint = value;
> +        return;
> +    }

no new line before else, new line before { though

> +    else if (pEvdev->mt_current_touchpoint < pEvdev->mt_max_touchpoints) {
> +        pEvdev->vals[pEvdev->axis_map[ev->code] +
> +            pEvdev->mt_current_touchpoint * pEvdev->mt_num_valuators] = value;

some helper variables maybe? I'm getting lost where which [ ends here.

> +    } else
> +        return; /* mt-event, but not enough place to store it */
> +


>      if (ev->code == ABS_X)
>          pEvdev->abs |= ABS_X_VALUE;
>      else if (ev->code == ABS_Y)
> @@ -1309,6 +1326,14 @@ EvdevMTInitValuators(DeviceIntPtr device, Atom *atoms)
>              pEvdev->old_vals[real_axnum] = -1;
>          }
>      }
> +
> +    /* TRACKING_ID != -1 means touch is down */
> +    for (j = 0; j < pEvdev->mt_max_touchpoints; j++) {
> +        int axnum = pEvdev->axis_map[ABS_MT_TRACKING_ID];
> +        int real_axnum = axnum + j * pEvdev->mt_num_valuators;
> +
> +        pEvdev->vals[real_axnum] = -1;
> +    }
>  }

As Benjamin said, EvdevMTInitValuators needs to cater for tracking IDs of
-1.
  
>  static int
> @@ -1329,6 +1354,10 @@ EvdevAddAbsClass(DeviceIntPtr device)
>      if (num_axes < 1)
>          return !Success;
>  
> +    /* We use slots internally to arrange touches into valuators */
> +    if (TestBit(ABS_MT_SLOT, pEvdev->abs_bitmask))
> +        num_axes--;
> +
>      num_axes = EvdevMTAddExtraValuators(pEvdev, num_axes);
>  
>      pEvdev->num_vals = num_axes;
> @@ -1338,7 +1367,8 @@ EvdevAddAbsClass(DeviceIntPtr device)
>  
>      for (axis = ABS_X; axis <= ABS_MAX; axis++) {
>          pEvdev->axis_map[axis] = -1;
> -        if (!TestBit(axis, pEvdev->abs_bitmask))
> +        /* We use slots internally to arrange touches into valuators */
> +        if (!TestBit(axis, pEvdev->abs_bitmask) || axis == ABS_MT_SLOT)
>              continue;
>          pEvdev->axis_map[axis] = i;
>          i++;
> diff --git a/src/evdev.h b/src/evdev.h
> index 7f9fc47..25c63a7 100644
> --- a/src/evdev.h
> +++ b/src/evdev.h
> @@ -197,6 +197,7 @@ typedef struct {
>      unsigned int mt_num_valuators;
>      unsigned int mt_max_touchpoints; /* the number of simultaneous touchpoints
>                                        * the device can support */
> +    unsigned int mt_current_touchpoint;
>  } EvdevRec, *EvdevPtr;
>  
>  /* Event posting functions */
> -- 
> 1.7.0.4
> 
Cheers,
  Peter