[PATCH libinput 3/3] touchpad: detect and warn about kernel tracking pointer jumps
Peter Hutterer
peter.hutterer at who-t.net
Wed Apr 27 10:36:50 UTC 2016
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 at who-t.net>
---
doc/Makefile.am | 1 +
doc/page-hierarchy.dox | 1 +
doc/touchpad-jumping-cursors.dox | 54 ++++++++++++++++++++++++++++++++++++++++
src/evdev-mt-touchpad.c | 27 ++++++++++++++++++++
test/touchpad.c | 39 +++++++++++++++++++++++++++++
5 files changed, 122 insertions(+)
create mode 100644 doc/touchpad-jumping-cursors.dox
diff --git a/doc/Makefile.am b/doc/Makefile.am
index 7a7c6cf..f56ed6a 100644
--- a/doc/Makefile.am
+++ b/doc/Makefile.am
@@ -27,6 +27,7 @@ header_files = \
$(srcdir)/tapping.dox \
$(srcdir)/test-suite.dox \
$(srcdir)/tools.dox \
+ $(srcdir)/touchpad-jumping-cursors.dox \
$(srcdir)/touchpads.dox
diagram_files = \
diff --git a/doc/page-hierarchy.dox b/doc/page-hierarchy.dox
index 1351a5e..e47e98e 100644
--- a/doc/page-hierarchy.dox
+++ b/doc/page-hierarchy.dox
@@ -7,6 +7,7 @@
- @subpage gestures
- @subpage palm_detection
- @subpage t440_support
+- @subpage touchpad_jumping_cursor
@page touchscreens Touchscreens
diff --git a/doc/touchpad-jumping-cursors.dox b/doc/touchpad-jumping-cursors.dox
new file mode 100644
index 0000000..e581eb1
--- /dev/null
+++ b/doc/touchpad-jumping-cursors.dox
@@ -0,0 +1,54 @@
+/**
+ at page touchpad_jumping_cursor Touchpad jumping cursor bugs
+
+A common bug encountered on touchpads is a cursor jump when alternating
+between fingers on a multi-touch-capable touchpad. For example, after moving
+the cursor a user may use a second finger in the software button area to
+physically click the touchpad. Upon setting the finger down, the cursor
+exhibits a jump towards the bottom left or right, depending on the finger
+position.
+
+When libinput detects a cursor jump it prints a bug warning to the log with
+the text <b>"Touch jump detected and discarded."</b> and a link to this page.
+
+In most cases, this is a bug in the kernel driver and to libinput it appears
+that the touch point moves from its previous position. The pointer jump can
+usually be seen in the evemu-record output for the device:
+
+<pre>
+ E: 249.206319 0000 0000 0000 # ------------ SYN_REPORT (0) ----------
+ E: 249.218008 0003 0035 3764 # EV_ABS / ABS_MT_POSITION_X 3764
+ E: 249.218008 0003 0036 2221 # EV_ABS / ABS_MT_POSITION_Y 2221
+ E: 249.218008 0003 003a 0065 # EV_ABS / ABS_MT_PRESSURE 65
+ E: 249.218008 0003 0000 3764 # EV_ABS / ABS_X 3764
+ E: 249.218008 0003 0001 2216 # EV_ABS / ABS_Y 2216
+ E: 249.218008 0003 0018 0065 # EV_ABS / ABS_PRESSURE 65
+ E: 249.218008 0000 0000 0000 # ------------ SYN_REPORT (0) ----------
+ E: 249.230881 0003 0035 3752 # EV_ABS / ABS_MT_POSITION_X 3752
+ E: 249.230881 0003 003a 0046 # EV_ABS / ABS_MT_PRESSURE 46
+ E: 249.230881 0003 0000 3758 # EV_ABS / ABS_X 3758
+ E: 249.230881 0003 0018 0046 # EV_ABS / ABS_PRESSURE 46
+ E: 249.230881 0000 0000 0000 # ------------ SYN_REPORT (0) ----------
+ E: 249.242648 0003 0035 1640 # EV_ABS / ABS_MT_POSITION_X 1640
+ E: 249.242648 0003 0036 4681 # EV_ABS / ABS_MT_POSITION_Y 4681
+ E: 249.242648 0003 003a 0025 # EV_ABS / ABS_MT_PRESSURE 25
+ E: 249.242648 0003 0000 1640 # EV_ABS / ABS_X 1640
+ E: 249.242648 0003 0001 4681 # EV_ABS / ABS_Y 4681
+ E: 249.242648 0003 0018 0025 # EV_ABS / ABS_PRESSURE 25
+ E: 249.242648 0000 0000 0000 # ------------ SYN_REPORT (0) ----------
+ E: 249.254568 0003 0035 1648 # EV_ABS / ABS_MT_POSITION_X 1648
+ E: 249.254568 0003 003a 0027 # EV_ABS / ABS_MT_PRESSURE 27
+ E: 249.254568 0003 0000 1644 # EV_ABS / ABS_X 1644
+ E: 249.254568 0003 0018 0027 # EV_ABS / ABS_PRESSURE 27
+</pre>
+
+In this recording, the pointer jumps from its position 3752/2216 to
+1640/4681 within a single frame. On this particular touchpad, this would
+represent a physical move of almost 50mm. libinput detects some of these
+jumps and discards the movement but otherwise continues as usual. However,
+the bug should be fixed at the kernel level.
+
+When you encounter the warning in the log, please generate an evemu
+recording of your touchpad and file a bug. See @ref reporting_bugs for more
+details.
+*/
diff --git a/src/evdev-mt-touchpad.c b/src/evdev-mt-touchpad.c
index 1974e2a..4c8c3a3 100644
--- a/src/evdev-mt-touchpad.c
+++ b/src/evdev-mt-touchpad.c
@@ -906,6 +906,25 @@ tp_need_motion_history_reset(struct tp_dispatch *tp)
return rc;
}
+static bool
+tp_detect_jumps(const struct tp_dispatch *tp, struct tp_touch *t)
+{
+ struct device_coords *last;
+ double dx, dy;
+ const int JUMP_THRESHOLD_MM = 20;
+
+ if (t->history.count == 0)
+ return false;
+
+ /* called before tp_motion_history_push, so offset 0 is the most
+ * recent coordinate */
+ last = tp_motion_history_offset(t, 0);
+ dx = fabs(t->point.x - last->x) / tp->device->abs.absinfo_x->resolution;
+ dy = fabs(t->point.y - last->y) / tp->device->abs.absinfo_y->resolution;
+
+ return hypot(dx, dy) > JUMP_THRESHOLD_MM;
+}
+
static void
tp_process_state(struct tp_dispatch *tp, uint64_t time)
{
@@ -937,6 +956,14 @@ tp_process_state(struct tp_dispatch *tp, uint64_t time)
if (t->pressure_delta < -7)
tp_motion_history_reset(t);
+ if (tp_detect_jumps(tp, t)) {
+ log_bug_kernel(tp_libinput_context(tp),
+ "Touch jump detected and discarded.\n"
+ "See %stouchpad_jumping_cursor for details\n",
+ HTTP_DOC_LINK);
+ tp_motion_history_reset(t);
+ }
+
tp_thumb_detect(tp, t, time);
tp_palm_detect(tp, t, time);
diff --git a/test/touchpad.c b/test/touchpad.c
index 6f483ee..2dbb346 100644
--- a/test/touchpad.c
+++ b/test/touchpad.c
@@ -4024,6 +4024,43 @@ START_TEST(touchpad_time_usec)
}
END_TEST
+START_TEST(touchpad_jump_finger_motion)
+{
+ struct litest_device *dev = litest_current_device();
+ struct libinput *li = dev->libinput;
+ struct libinput_event *event;
+ struct libinput_event_pointer *ptrev;
+
+ litest_touch_down(dev, 0, 20, 30);
+ litest_touch_move_to(dev, 0, 20, 30, 90, 30, 10, 0);
+ litest_drain_events(li);
+
+ litest_disable_log_handler(li);
+ litest_touch_move_to(dev, 0, 90, 30, 20, 80, 1, 0);
+ litest_assert_empty_queue(li);
+ litest_restore_log_handler(li);
+
+ litest_touch_move_to(dev, 0, 20, 80, 21, 81, 10, 0);
+ litest_touch_up(dev, 0);
+
+ /* expect lots of little events, no big jump */
+ libinput_dispatch(li);
+ event = libinput_get_event(li);
+ do {
+ double dx, dy;
+
+ ptrev = litest_is_motion_event(event);
+ dx = libinput_event_pointer_get_dx(ptrev);
+ dy = libinput_event_pointer_get_dy(ptrev);
+ ck_assert_int_lt(abs(dx), 20);
+ ck_assert_int_lt(abs(dy), 20);
+
+ libinput_event_destroy(event);
+ event = libinput_get_event(li);
+ } while (event != NULL);
+}
+END_TEST
+
void
litest_setup_tests(void)
{
@@ -4144,4 +4181,6 @@ litest_setup_tests(void)
litest_add_for_device("touchpad:bugs", touchpad_t450_motion_drops, LITEST_SYNAPTICS_TRACKPOINT_BUTTONS);
litest_add("touchpad:time", touchpad_time_usec, LITEST_TOUCHPAD, LITEST_ANY);
+
+ litest_add_for_device("touchpad:jumps", touchpad_jump_finger_motion, LITEST_SYNAPTICS_CLICKPAD);
}
--
2.7.4
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