[PATCH] touchpad: Only use slot 0 deltas for 2fg scrolling on semi-mt touchpads

[Peter Hutterer]

On Fri, Apr 24, 2015 at 04:49:36PM +0200, Hans de Goede wrote:
> Some semi-mt model touchpads have a better accuracy for slot 0 then for
> slot 1 (they only have 2), so on semi-mt models only use the movement of
> the touch in slot 0 for 2fg scrolling, rather then the average movement of
> the 2 touches.
> 
> This fixes 2fg scrolling being choppy / jumpy in some cases.
> 
> BugLink: https://bugs.freedesktop.org/show_bug.cgi?id=89683
> Signed-off-by: Hans de Goede <hdegoede at redhat.com>
> ---
>  src/evdev-mt-touchpad-gestures.c | 12 +++++++++++-
>  1 file changed, 11 insertions(+), 1 deletion(-)
> 
> diff --git a/src/evdev-mt-touchpad-gestures.c b/src/evdev-mt-touchpad-gestures.c
> index d332186..57c07fe 100644
> --- a/src/evdev-mt-touchpad-gestures.c
> +++ b/src/evdev-mt-touchpad-gestures.c
> @@ -113,7 +113,17 @@ tp_gesture_post_twofinger_scroll(struct tp_dispatch *tp, uint64_t time)
>  	if (tp->scroll.method != LIBINPUT_CONFIG_SCROLL_2FG)
>  		return;
>  
> -	delta = tp_get_average_touches_delta(tp);
> +	/* On some semi-mt models slot 0 is more accurate, so for semi-mt
> +	 * we only use slot 0. */
> +	if (tp->semi_mt) {
> +		if (!tp->touches[0].dirty)
> +			return;
> +
> +		delta = tp_get_delta(&tp->touches[0]);
> +	} else {
> +		delta = tp_get_average_touches_delta(tp);
> +	}
> +
>  	delta = tp_filter_motion(tp, &delta, time);
>  
>  	if (normalized_is_zero(delta))
> -- 
> 2.3.5
 
pushed, thanks. I had to fix one of the tests since it kept failing here
(see commit 07b20dc) and in the process added a test for this behaviour as
follow-up.

Cheers,
   Peter