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touchpad: normalize the touchpad resolution to 400dpi, not 10 units/mm

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In an attempt to bring method into the madness, normalize the touchpad deltas
to those of a USB mouse with 400 dpi. This way the data we're dealing with in
the acceleration code is of a known quantity.

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
This commit is contained in:
Peter Hutterer 2014-07-08 13:43:45 +10:00
parent 468e628808
commit e874d09b49
3 changed files with 18 additions and 8 deletions
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15
src/evdev-mt-touchpad.c
View file

@ -663,14 +663,17 @@ tp_init_accel(struct tp_dispatch *tp, double diagonal)
/*
* Not all touchpads report the same amount of units/mm (resolution).
* Normalize motion events to a resolution of 10 units/mm as base
* (unaccelerated) speed. This also evens out any differences in x
* and y resolution, so that a circle on the touchpad does not turn
* into an elipse on the screen.
* Normalize motion events to a resolution of 15.74 units/mm
* (== 400 dpi) as base (unaccelerated) speed. This also evens out any
* differences in x and y resolution, so that a circle on the
* touchpad does not turn into an elipse on the screen.
*
* We pick 400dpi as thats one of the many default resolutions
* for USB mice, so we end up with a similar base speed on the device.
*/
if (res_x > 1 && res_y > 1) {
tp->accel.x_scale_coeff = 10.0 / res_x;
tp->accel.y_scale_coeff = 10.0 / res_y;
tp->accel.x_scale_coeff = (400/25.4) / res_x;
tp->accel.y_scale_coeff = (400/25.4) / res_y;
} else {
/*
* For touchpads where the driver does not provide resolution, fall

9
src/filter.c
View file

@ -341,7 +341,14 @@ pointer_accel_profile_smooth_simple(struct motion_filter *filter,
if (accel < 1.0)
accel = 1.0;
/* We use units/ms as velocity but it has no real meaning unless all
devices have the same resolution. For touchpads, we normalize to
400dpi (15.75 units/mm), but the resolution on USB mice is all
over the place. Though most mice these days have either 400
dpi (15.75 units/mm), 800 dpi or 1000dpi, excluding gaming mice
that can usually adjust it on the fly anyway and currently go up
to 8200dpi.
*/
if (velocity < (threshold / 2.0))
return calc_penumbral_gradient(0.5 + velocity / threshold) * 2.0 - 1.0;

2
src/filter.h
View file

@ -26,7 +26,7 @@
#include "config.h"
struct motion_params {
double dx, dy;
double dx, dy; /* in units/ms @ 400dpi */
};
struct motion_filter;