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touchpad: add wobbling detection

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The details are explained in comment in the code. That aside, I shall
mention the check is so light, that it shouldn't influence CPU
performance even a bit, and can blindly be kept always enabled.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=104828

Signed-off-by: Konstantin Kharlamov <Hi-Angel@yandex.ru>
Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Reviewed-by: Konstantin Kharlamov <Hi-Angel@yandex.ru>
This commit is contained in:
Konstantin Kharlamov 2018-02-21 20:16:41 +03:00 • committed by Peter Hutterer
parent e8dffbd73a
commit 400aadd53a
2 changed files with 59 additions and 1 deletions
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58
src/evdev-mt-touchpad.c
View file

@ -135,6 +135,61 @@ tp_motion_history_push(struct tp_touch *t)
t->history.index = motion_index;
}
/* Idea: if we got a tuple of *very* quick moves like {Left, Right,
* Left}, or {Right, Left, Right}, it means touchpad jitters since no
* human can move like that within thresholds.
*
* We encode left moves as zeroes, and right as ones. We also drop
* the array to all zeroes when contraints are not satisfied. Then we
* search for the pattern {1,0,1}. It can't match {Left, Right, Left},
* but it does match {Left, Right, Left, Right}, so it's okay.
*
* This only looks at x changes, y changes are ignored.
*/
static inline void
tp_detect_wobbling(struct tp_dispatch *tp,
struct tp_touch *t,
uint64_t time)
{
int dx, dy;
uint64_t dtime;
if (!(tp->queued & TOUCHPAD_EVENT_MOTION) || tp->hysteresis.enabled)
return;
if (t->last_point.x == 0) { /* first invocation */
dx = 0;
dy = 0;
} else {
dx = t->last_point.x - t->point.x;
dy = t->last_point.y - t->point.y;
}
dtime = time - tp->hysteresis.last_motion_time;
tp->hysteresis.last_motion_time = time;
t->last_point = t->point;
if (dx == 0 && dy != 0) /* ignore y-only changes */
return;
if (dtime > ms2us(40)) {
t->hysteresis.x_motion_history = 0;
return;
}
t->hysteresis.x_motion_history <<= 1;
if (dx > 0) { /* right move */
static const char r_l_r = 0x5; /* {Right, Left, Right} */
t->hysteresis.x_motion_history |= 0x1;
if (t->hysteresis.x_motion_history == r_l_r) {
tp->hysteresis.enabled = true;
evdev_log_debug(tp->device, "hysteresis enabled\n");
}
}
}
static inline void
tp_motion_hysteresis(struct tp_dispatch *tp,
struct tp_touch *t)
@ -265,6 +320,7 @@ tp_new_touch(struct tp_dispatch *tp, struct tp_touch *t, uint64_t time)
t->time = time;
t->speed.last_speed = 0;
t->speed.exceeded_count = 0;
t->hysteresis.x_motion_history = 0;
tp->queued |= TOUCHPAD_EVENT_MOTION;
}
@ -1443,7 +1499,7 @@ tp_process_state(struct tp_dispatch *tp, uint64_t time)
tp_thumb_detect(tp, t, time);
tp_palm_detect(tp, t, time);
tp_detect_wobbling(tp, t, time);
tp_motion_hysteresis(tp, t);
tp_motion_history_push(t);

2
src/evdev-mt-touchpad.h
View file

@ -149,6 +149,7 @@ struct tp_touch {
bool has_ended; /* TRACKING_ID == -1 */
bool dirty;
struct device_coords point;
struct device_coords last_point;
uint64_t time;
int pressure;
bool is_tool_palm; /* MT_TOOL_PALM */
@ -177,6 +178,7 @@ struct tp_touch {
struct {
struct device_coords center;
uint8_t x_motion_history;
} hysteresis;
/* A pinned touchpoint is the one that pressed the physical button