[PATCH] gestures: if fingers don't move, force a gesture by finger position

[Peter Hutterer]

On Tue, Dec 20, 2016 at 12:20:38PM +0100, Hans de Goede wrote:
> Hi,
> 
> On 20-12-16 04:57, Peter Hutterer wrote:
> > If the fingers rest on the touchpad without moving for a timeout, switch to
> > pinch or swipe based on the finger position. We already did so for two-fingers
> > switching to scrolling, now we also do so for 3 and 4 finger gestures. This
> > gives us better reaction to small movements.
> > 
> > Signed-off-by: Peter Hutterer <peter.hutterer at who-t.net>
> > ---
> >  src/evdev-mt-touchpad-gestures.c | 10 ++++++----
> >  1 file changed, 6 insertions(+), 4 deletions(-)
> > 
> > diff --git a/src/evdev-mt-touchpad-gestures.c b/src/evdev-mt-touchpad-gestures.c
> > index 6c568a3..e54db2a 100644
> > --- a/src/evdev-mt-touchpad-gestures.c
> > +++ b/src/evdev-mt-touchpad-gestures.c
> > @@ -331,10 +331,10 @@ tp_gesture_handle_state_unknown(struct tp_dispatch *tp, uint64_t time)
> >  	int yres = tp->device->abs.absinfo_y->resolution;
> >  	int vert_distance;
> > 
> > -	/* for two-finger gestures, if the fingers stay unmoving for a
> > -	 * while, assume (slow) scroll */
> > -	if (tp->gesture.finger_count == 2) {
> > -		if (time > (tp->gesture.initial_time + DEFAULT_GESTURE_2FG_SCROLL_TIMEOUT)) {
> > +	if (time > (tp->gesture.initial_time + DEFAULT_GESTURE_2FG_SCROLL_TIMEOUT)) {
> > +		/* for two-finger gestures, if the fingers stay unmoving for a
> > +		 * while, assume (slow) scroll */
> > +		if (tp->gesture.finger_count == 2) {
> >  			tp_gesture_set_scroll_buildup(tp);
> >  			return GESTURE_STATE_SCROLL;
> >  		}
> > @@ -346,6 +346,8 @@ tp_gesture_handle_state_unknown(struct tp_dispatch *tp, uint64_t time)
> >  		    tp->gesture.enabled) {
> >  			tp_gesture_init_pinch(tp);
> >  			return GESTURE_STATE_PINCH;
> > +		} else {
> > +			return GESTURE_STATE_SWIPE;
> >  		}
> >  	}
> > 
> > 
> 
> This change means that if 2 fingers are down and one finger is > 20mm below the others, we
> will no longer immediately switch to pinch mode, as that test is now only done after the
> timeout. I think that that is an unintended side-effect of this patch ?

Huh, I didn't think it was. I just double-checked that and realised that the
previous bit was broken anyway but it's not visible in the patch context.
The full condition is:
    if (vert_distance > 20 * yres &&
        tp->gesture.finger_count > 2 &&
        tp->gesture.enabled) {
        tp_gesture_init_pinch(tp);
         return GESTURE_STATE_PINCH;

but that was inside a "if (tp->gesture.finger_count == 2)" block so this
code was never triggered. Apparently we don't have a test case for this one.
The new code is:
   if (timeout expired) {
        if two fingers -> return scroll

        if vertical distance -> return pinch
        else return swipe
   }

I'll clean this up and re-send, thanks.

Another note: the reason we can't switch to pinch immediately for 2 fingers
is that when you put 3 fingers down for a swipe, it's likely you put down
one, then two, then 3 fingers. So there's a chance that you could switch to
pinch before the third finger is down. We work around this by
looking at the left/right touches only and thus ignoring the middle finger
but that doesn't work during the transitional phase.

Cheers,
   Peter