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

[Jonas Ådahl]

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.

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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