[PATCH libinput 05/16] filter: add two helper functions to convert between speeds

[Peter Hutterer]

On Mon, Aug 10, 2015 at 04:21:17PM +0800, Jonas Ådahl wrote:
> On Wed, Aug 05, 2015 at 04:32:34PM +1000, Peter Hutterer wrote:
> > This makes it more obvious where we're using units/us and units/ms as input
> > variable and what the output is. Clutters up the code, but still better than
> > dealing with us/ms differently per function, and still better than carrying
> > all the 1000.0 multiplications/divisions manually.
> > 
> > Signed-off-by: Peter Hutterer <peter.hutterer at who-t.net>
> > ---
> >  src/filter.c | 38 ++++++++++++++++++++++++++++----------
> >  1 file changed, 28 insertions(+), 10 deletions(-)
> > 
> > diff --git a/src/filter.c b/src/filter.c
> > index d55497e..b42db35 100644
> > --- a/src/filter.c
> > +++ b/src/filter.c
> > @@ -36,6 +36,20 @@
> >  #include "libinput-util.h"
> >  #include "filter-private.h"
> >  
> > +/* Convert speed/velocity from units/us to units/ms */
> > +static inline double
> > +v_us2ms(double units_per_us)
> > +{
> > +	return units_per_us * 1000.0;
> > +}
> > +
> > +/* Convert speed/velocity from units/ms to units/us */
> > +static inline double
> > +v_ms2us(double units_per_ms)
> > +{
> > +	return units_per_ms/1000.0;
> > +}
> > +
> >  struct normalized_coords
> >  filter_dispatch(struct motion_filter *filter,
> >  		const struct normalized_coords *unaccelerated,
> > @@ -77,8 +91,8 @@ filter_get_speed(struct motion_filter *filter)
> >   * Default parameters for pointer acceleration profiles.
> >   */
> >  
> > -#define DEFAULT_THRESHOLD 0.0004		/* in units/us */
> > -#define MINIMUM_THRESHOLD 0.0002		/* in units/us */
> > +#define DEFAULT_THRESHOLD v_ms2us(0.4)		/* in units/us */
> > +#define MINIMUM_THRESHOLD v_ms2us(0.2)		/* in units/us */
> >  #define DEFAULT_ACCELERATION 2.0		/* unitless factor */
> >  #define DEFAULT_INCLINE 1.1			/* unitless factor */
> >  
> > @@ -86,7 +100,7 @@ filter_get_speed(struct motion_filter *filter)
> >   * Pointer acceleration filter constants
> >   */
> >  
> > -#define MAX_VELOCITY_DIFF	0.001 /* units/us */
> > +#define MAX_VELOCITY_DIFF	v_ms2us(1) /* units/us */
> >  #define MOTION_TIMEOUT		ms2us(1000)
> >  #define NUM_POINTER_TRACKERS	16
> >  
> > @@ -332,8 +346,12 @@ accelerator_set_speed(struct motion_filter *filter,
> >  
> >  	assert(speed_ranged >= -1.0 && speed_ranged <= 1.0);
> >  
> > +	/* Note: the numbers below are nothing but trial-and-error magic,
> > +	   don't read more into them other than "they mostly worked ok" */
> > +
> >  	/* delay when accel kicks in */
> > -	accel_filter->threshold = DEFAULT_THRESHOLD - speed_ranged / 4000.0;
> > +	accel_filter->threshold = DEFAULT_THRESHOLD -
> > +					v_ms2us(speed_ranged / 4.0);
> 
> Is "speed_ranged" really in units/ms? I think it might make more sense
> to make it speed_ranged * v_ms2us(1/4), to make it more explicit that it
> is not.

hah, good point, that was bothering me anyway but I just didn't click on the
easy solution. fixed now, thanks.

Cheers,
   Peter

> 
> Otherwise this is also Reviewed-by: Jonas Ådahl <jadahl at gmail.com>
> 
> 
> Jonas
> 
> >  	if (accel_filter->threshold < MINIMUM_THRESHOLD)
> >  		accel_filter->threshold = MINIMUM_THRESHOLD;
> >  
> > @@ -412,8 +430,8 @@ pointer_accel_profile_linear_low_dpi(struct motion_filter *filter,
> >  
> >  	max_accel /= dpi_factor;
> >  
> > -	f1 = min(1, 0.3 + speed_in * 10000.0);
> > -	f2 = 1 + (speed_in * 1000.0 - threshold * dpi_factor * 1000.0) * incline;
> > +	f1 = min(1, 0.3 + v_us2ms(speed_in) * 10.0);
> > +	f2 = 1 + (v_us2ms(speed_in) - v_us2ms(threshold) * dpi_factor) * incline;
> >  
> >  	factor = min(max_accel, f2 > 1 ? f2 : f1);
> >  
> > @@ -435,8 +453,8 @@ pointer_accel_profile_linear(struct motion_filter *filter,
> >  	const double incline = accel_filter->incline;
> >  	double factor; /* unitless */
> >  
> > -	f1 = min(1, 0.3 + speed_in * 10 * 1000.0);
> > -	f2 = 1 + (speed_in * 1000.0 - threshold * 1000.0) * incline;
> > +	f1 = min(1, 0.3 + v_us2ms(speed_in) * 10);
> > +	f2 = 1 + (v_us2ms(speed_in) - v_us2ms(threshold)) * incline;
> >  
> >  	factor = min(max_accel, f2 > 1 ? f2 : f1);
> >  
> > @@ -493,8 +511,8 @@ touchpad_lenovo_x230_accel_profile(struct motion_filter *filter,
> >  
> >  	speed_in *= TP_MAGIC_SLOWDOWN / TP_MAGIC_LOW_RES_FACTOR;
> >  
> > -	f1 = min(1, speed_in * 5 * 1000.0);
> > -	f2 = 1 + (speed_in  * 1000.0 - threshold * 1000.0) * incline;
> > +	f1 = min(1, v_us2ms(speed_in) * 5);
> > +	f2 = 1 + (v_us2ms(speed_in) - v_us2ms(threshold)) * incline;
> >  
> >  	factor = min(max_accel, f2 > 1 ? f2 : f1);
> >  
> > -- 
> > 2.4.3
> > 
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