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touchpad: detect and warn about kernel tracking pointer jumps
If a touch moves by more than 20mm within a single frame, reset the motion history, effectively discarding the movement. This is a relatively common bug and almost always needs a kernel fix, so add an explanatory page to the docs. Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net> Reviewed-by: Benjamin Tissoires <benjamin.tissoires@gmail.com> Reviewed-by: Hans de Goede <hdegoede@redhat.com>
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Peter Hutterer
parent
774be50e68
commit
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5 changed files with 122 additions and 0 deletions
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@ -27,6 +27,7 @@ header_files = \
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$(srcdir)/tapping.dox \
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$(srcdir)/test-suite.dox \
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$(srcdir)/tools.dox \
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$(srcdir)/touchpad-jumping-cursors.dox \
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$(srcdir)/touchpads.dox
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diagram_files = \
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@ -7,6 +7,7 @@
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- @subpage gestures
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- @subpage palm_detection
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- @subpage t440_support
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- @subpage touchpad_jumping_cursor
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@page touchscreens Touchscreens
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54
doc/touchpad-jumping-cursors.dox
Normal file
54
doc/touchpad-jumping-cursors.dox
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@ -0,0 +1,54 @@
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/**
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@page touchpad_jumping_cursor Touchpad jumping cursor bugs
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A common bug encountered on touchpads is a cursor jump when alternating
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between fingers on a multi-touch-capable touchpad. For example, after moving
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the cursor a user may use a second finger in the software button area to
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physically click the touchpad. Upon setting the finger down, the cursor
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exhibits a jump towards the bottom left or right, depending on the finger
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position.
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When libinput detects a cursor jump it prints a bug warning to the log with
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the text <b>"Touch jump detected and discarded."</b> and a link to this page.
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In most cases, this is a bug in the kernel driver and to libinput it appears
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that the touch point moves from its previous position. The pointer jump can
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usually be seen in the evemu-record output for the device:
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<pre>
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E: 249.206319 0000 0000 0000 # ------------ SYN_REPORT (0) ----------
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E: 249.218008 0003 0035 3764 # EV_ABS / ABS_MT_POSITION_X 3764
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E: 249.218008 0003 0036 2221 # EV_ABS / ABS_MT_POSITION_Y 2221
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E: 249.218008 0003 003a 0065 # EV_ABS / ABS_MT_PRESSURE 65
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E: 249.218008 0003 0000 3764 # EV_ABS / ABS_X 3764
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E: 249.218008 0003 0001 2216 # EV_ABS / ABS_Y 2216
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E: 249.218008 0003 0018 0065 # EV_ABS / ABS_PRESSURE 65
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E: 249.218008 0000 0000 0000 # ------------ SYN_REPORT (0) ----------
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E: 249.230881 0003 0035 3752 # EV_ABS / ABS_MT_POSITION_X 3752
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E: 249.230881 0003 003a 0046 # EV_ABS / ABS_MT_PRESSURE 46
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E: 249.230881 0003 0000 3758 # EV_ABS / ABS_X 3758
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E: 249.230881 0003 0018 0046 # EV_ABS / ABS_PRESSURE 46
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E: 249.230881 0000 0000 0000 # ------------ SYN_REPORT (0) ----------
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E: 249.242648 0003 0035 1640 # EV_ABS / ABS_MT_POSITION_X 1640
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E: 249.242648 0003 0036 4681 # EV_ABS / ABS_MT_POSITION_Y 4681
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E: 249.242648 0003 003a 0025 # EV_ABS / ABS_MT_PRESSURE 25
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E: 249.242648 0003 0000 1640 # EV_ABS / ABS_X 1640
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E: 249.242648 0003 0001 4681 # EV_ABS / ABS_Y 4681
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E: 249.242648 0003 0018 0025 # EV_ABS / ABS_PRESSURE 25
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E: 249.242648 0000 0000 0000 # ------------ SYN_REPORT (0) ----------
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E: 249.254568 0003 0035 1648 # EV_ABS / ABS_MT_POSITION_X 1648
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E: 249.254568 0003 003a 0027 # EV_ABS / ABS_MT_PRESSURE 27
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E: 249.254568 0003 0000 1644 # EV_ABS / ABS_X 1644
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E: 249.254568 0003 0018 0027 # EV_ABS / ABS_PRESSURE 27
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</pre>
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In this recording, the pointer jumps from its position 3752/2216 to
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1640/4681 within a single frame. On this particular touchpad, this would
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represent a physical move of almost 50mm. libinput detects some of these
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jumps and discards the movement but otherwise continues as usual. However,
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the bug should be fixed at the kernel level.
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When you encounter the warning in the log, please generate an evemu
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recording of your touchpad and file a bug. See @ref reporting_bugs for more
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details.
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*/
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@ -906,6 +906,25 @@ tp_need_motion_history_reset(struct tp_dispatch *tp)
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return rc;
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}
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static bool
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tp_detect_jumps(const struct tp_dispatch *tp, struct tp_touch *t)
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{
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struct device_coords *last;
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double dx, dy;
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const int JUMP_THRESHOLD_MM = 20;
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if (t->history.count == 0)
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return false;
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/* called before tp_motion_history_push, so offset 0 is the most
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* recent coordinate */
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last = tp_motion_history_offset(t, 0);
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dx = fabs(t->point.x - last->x) / tp->device->abs.absinfo_x->resolution;
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dy = fabs(t->point.y - last->y) / tp->device->abs.absinfo_y->resolution;
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return hypot(dx, dy) > JUMP_THRESHOLD_MM;
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}
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static void
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tp_process_state(struct tp_dispatch *tp, uint64_t time)
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{
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@ -937,6 +956,14 @@ tp_process_state(struct tp_dispatch *tp, uint64_t time)
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if (t->pressure_delta < -7)
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tp_motion_history_reset(t);
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if (tp_detect_jumps(tp, t)) {
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log_bug_kernel(tp_libinput_context(tp),
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"Touch jump detected and discarded.\n"
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"See %stouchpad_jumping_cursor for details\n",
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HTTP_DOC_LINK);
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tp_motion_history_reset(t);
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}
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tp_thumb_detect(tp, t, time);
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tp_palm_detect(tp, t, time);
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@ -4024,6 +4024,43 @@ START_TEST(touchpad_time_usec)
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}
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END_TEST
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START_TEST(touchpad_jump_finger_motion)
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{
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struct litest_device *dev = litest_current_device();
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struct libinput *li = dev->libinput;
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struct libinput_event *event;
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struct libinput_event_pointer *ptrev;
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litest_touch_down(dev, 0, 20, 30);
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litest_touch_move_to(dev, 0, 20, 30, 90, 30, 10, 0);
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litest_drain_events(li);
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litest_disable_log_handler(li);
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litest_touch_move_to(dev, 0, 90, 30, 20, 80, 1, 0);
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litest_assert_empty_queue(li);
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litest_restore_log_handler(li);
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litest_touch_move_to(dev, 0, 20, 80, 21, 81, 10, 0);
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litest_touch_up(dev, 0);
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/* expect lots of little events, no big jump */
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libinput_dispatch(li);
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event = libinput_get_event(li);
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do {
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double dx, dy;
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ptrev = litest_is_motion_event(event);
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dx = libinput_event_pointer_get_dx(ptrev);
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dy = libinput_event_pointer_get_dy(ptrev);
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ck_assert_int_lt(abs(dx), 20);
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ck_assert_int_lt(abs(dy), 20);
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libinput_event_destroy(event);
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event = libinput_get_event(li);
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} while (event != NULL);
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}
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END_TEST
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void
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litest_setup_tests(void)
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{
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@ -4144,4 +4181,6 @@ litest_setup_tests(void)
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litest_add_for_device("touchpad:bugs", touchpad_t450_motion_drops, LITEST_SYNAPTICS_TRACKPOINT_BUTTONS);
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litest_add("touchpad:time", touchpad_time_usec, LITEST_TOUCHPAD, LITEST_ANY);
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litest_add_for_device("touchpad:jumps", touchpad_jump_finger_motion, LITEST_SYNAPTICS_CLICKPAD);
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}
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