From: Konstantin Kharlamov <hi-an...@yandex.ru> 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 v2: rename the function, change comment style, and add calculation of x_diff (the one that was used is an absolute coordinate). FWIW, the algorithm don't care that now added "prev_x" is unintialized, because that happening means the time threshold won't get satisfied either. It's not like I can't default-init it — it's just that asking oneself a question "what default value should it have" results in "none". v3: * style fixes (empty line after a block, declaration at top) * s/x_diff/dx * s/x_motion_in_threashold/x_motion_history * compare with r_l_r instead of & * store whole point instead of just x * move x_motion_history and prev_coords into tp_touch * move everything around tp_detect_wobbling() call into the function, use goto for that purpose. * per request: add a comparison for when previous coordinates don't actually have the prev. coordinates yet. * increased timeout from 20ms to 40ms just in case — it's still out of human ability anyway, and in fact can be increased even further * ignore Y-only changes, again just in case — it could happen that Y and X events would be sent separately, and break the heuristic. v4: * some more style fixes Signed-off-by: Konstantin Kharlamov <hi-an...@yandex.ru> Signed-off-by: Peter Hutterer <peter.hutte...@who-t.net> --- Changes to v3: - more style fixes - ajudsted for patch 1/3 src/evdev-mt-touchpad.c | 58 ++++++++++++++++++++++++++++++++++++++++++++++++- src/evdev-mt-touchpad.h | 2 ++ 2 files changed, 59 insertions(+), 1 deletion(-) diff --git a/src/evdev-mt-touchpad.c b/src/evdev-mt-touchpad.c index 0c3e6a2b..cec4ba34 100644 --- a/src/evdev-mt-touchpad.c +++ b/src/evdev-mt-touchpad.c @@ -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); diff --git a/src/evdev-mt-touchpad.h b/src/evdev-mt-touchpad.h index 3ce893d2..1fd8f1e3 100644 --- a/src/evdev-mt-touchpad.h +++ b/src/evdev-mt-touchpad.h @@ -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 -- 2.14.3 _______________________________________________ wayland-devel mailing list wayland-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/wayland-devel
