[PATCH libinput] touchpad: don't allow taps in the top half of the palm exclusion zone.

Peter Hutterer peter.hutterer at who-t.net
Tue Apr 14 22:55:03 PDT 2015


Touches in the exclusion zone are ignored for palm detection and don't move
the cursor. Tapping however triggers before we know whether something is a
palm or not, so we get erroneous button clickst.

If a tap happens in the top half of the touchpad, within the palm exclusion
zones, ignore it for tap purposes. To avoid further complicating the state
machine simply pretend there was a movement > threshold on that finger. This
advances the tap state machine properly that no button events are sent for
this finger.

https://bugs.freedesktop.org/show_bug.cgi?id=89625

Signed-off-by: Peter Hutterer <peter.hutterer at who-t.net>
---
 doc/palm-detection.dox      |   9 ++
 doc/svg/palm-detection.svg  | 213 ++++++++++++++++++++++++++++++++------------
 src/evdev-mt-touchpad-tap.c |   8 ++
 src/evdev-mt-touchpad.c     |  24 ++++-
 src/evdev-mt-touchpad.h     |   4 +
 test/touchpad.c             |  44 +++++++++
 6 files changed, 244 insertions(+), 58 deletions(-)

diff --git a/doc/palm-detection.dox b/doc/palm-detection.dox
index 4e839e6..a5b578b 100644
--- a/doc/palm-detection.dox
+++ b/doc/palm-detection.dox
@@ -23,6 +23,10 @@ screen, it is common for a finger to start inside an exclusion zone and move
 rapidly across the touchpad. libinput detects such movements and avoids palm
 detection on such touch sequences.
 
+Each exclusion zone is divided into a top part and a bottom part. A touch
+starting in the top part of the exclusion zone does not trigger a
+tap (see @ref tapping).
+
 In the diagram below, the exclusion zones are painted red.
 Touch 'A' starts inside the exclusion zone and moves
 almost vertically. It is considered a palm and ignored for cursor movement,
@@ -31,6 +35,11 @@ despite moving out of the exclusion zone.
 Touch 'B' starts inside the exclusion zone but moves horizontally out of the
 zone. It is considered a valid touch and controls the cursor.
 
+Touch 'C' occurs in the top part of the exclusion zone. Despite being a
+tapping motion, it does not generate an emulated button event. Touch 'D'
+likewise occurs within the exclusion zone but in the bottom half. libinput
+will generate a button event for this touch.
+
 @image html palm-detection.svg
 
 @section trackpoint-disabling Palm detection during trackpoint use
diff --git a/doc/svg/palm-detection.svg b/doc/svg/palm-detection.svg
index 9fb6077..c3e45f4 100644
--- a/doc/svg/palm-detection.svg
+++ b/doc/svg/palm-detection.svg
@@ -2,15 +2,67 @@
 <!-- Created with Inkscape (http://www.inkscape.org/) -->
 
 <svg
+   xmlns:dc="http://purl.org/dc/elements/1.1/"
+   xmlns:cc="http://creativecommons.org/ns#"
+   xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
    xmlns:svg="http://www.w3.org/2000/svg"
    xmlns="http://www.w3.org/2000/svg"
+   xmlns:sodipodi="http://sodipodi.sourceforge.net/DTD/sodipodi-0.dtd"
+   xmlns:inkscape="http://www.inkscape.org/namespaces/inkscape"
    version="1.1"
    width="393.62857"
    height="268.62857"
-   id="svg2">
+   id="svg2"
+   inkscape:version="0.91 r13725"
+   sodipodi:docname="palm-detection.svg">
+  <metadata
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+    <rdf:RDF>
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+  <sodipodi:namedview
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+     bordercolor="#666666"
+     borderopacity="1"
+     objecttolerance="10"
+     gridtolerance="10"
+     guidetolerance="10"
+     inkscape:pageopacity="0"
+     inkscape:pageshadow="2"
+     inkscape:window-width="1920"
+     inkscape:window-height="1136"
+     id="namedview3477"
+     showgrid="false"
+     inkscape:zoom="3.5662625"
+     inkscape:cx="199.35048"
+     inkscape:cy="156.74673"
+     inkscape:window-x="0"
+     inkscape:window-y="27"
+     inkscape:window-maximized="1"
+     inkscape:current-layer="svg2" />
   <defs
      id="defs4">
     <marker
+       inkscape:stockid="Arrow1Lstart"
+       orient="auto"
+       refY="0.0"
+       refX="0.0"
+       id="marker4663"
+       style="overflow:visible"
+       inkscape:isstock="true">
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+         transform="scale(0.8) translate(12.5,0)" />
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+    <marker
        refX="0"
        refY="0"
        orient="auto"
@@ -59,64 +111,111 @@
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diff --git a/src/evdev-mt-touchpad-tap.c b/src/evdev-mt-touchpad-tap.c
index 69c9669..49fabb5 100644
--- a/src/evdev-mt-touchpad-tap.c
+++ b/src/evdev-mt-touchpad-tap.c
@@ -571,6 +571,14 @@ tp_tap_handle_state(struct tp_dispatch *tp, uint64_t time)
 			t->tap.state = TAP_TOUCH_STATE_TOUCH;
 			t->tap.initial = t->point;
 			tp_tap_handle_event(tp, t, TAP_EVENT_TOUCH, time);
+
+			/* If we think this is a palm, pretend there's a
+			 * motion event which will prevent tap clicks
+			 * without requiring extra states in the FSM.
+			 */
+			if (tp_palm_tap_is_palm(tp, t))
+				tp_tap_handle_event(tp, t, TAP_EVENT_MOTION, time);
+
 		} else if (t->state == TOUCH_END) {
 			tp->tap.tap_finger_count--;
 			tp_tap_handle_event(tp, t, TAP_EVENT_RELEASE, time);
diff --git a/src/evdev-mt-touchpad.c b/src/evdev-mt-touchpad.c
index 68070c2..41f9767 100644
--- a/src/evdev-mt-touchpad.c
+++ b/src/evdev-mt-touchpad.c
@@ -458,6 +458,24 @@ tp_touch_active(struct tp_dispatch *tp, struct tp_touch *t)
 		tp_edge_scroll_touch_active(tp, t);
 }
 
+bool
+tp_palm_tap_is_palm(struct tp_dispatch *tp, struct tp_touch *t)
+{
+	if (t->state != TOUCH_BEGIN)
+		return false;
+
+	if (t->point.x > tp->palm.left_edge &&
+	    t->point.x < tp->palm.right_edge)
+		return false;
+
+	/* We're inside the left/right palm edge and in the northern half of
+	 * the touchpad - this tap is a palm */
+	if (t->point.y < tp->palm.vert_center)
+		return true;
+
+	return false;
+}
+
 static void
 tp_palm_detect(struct tp_dispatch *tp, struct tp_touch *t, uint64_t time)
 {
@@ -1091,13 +1109,16 @@ static int
 tp_init_palmdetect(struct tp_dispatch *tp,
 		   struct evdev_device *device)
 {
-	int width;
+	int width, height;
 
 	tp->palm.right_edge = INT_MAX;
 	tp->palm.left_edge = INT_MIN;
+	tp->palm.vert_center = INT_MIN;
 
 	width = abs(device->abs.absinfo_x->maximum -
 		    device->abs.absinfo_x->minimum);
+	height = abs(device->abs.absinfo_y->maximum -
+		    device->abs.absinfo_y->minimum);
 
 	/* Apple touchpads are always big enough to warrant palm detection */
 	if (evdev_device_get_id_vendor(device) != VENDOR_ID_APPLE) {
@@ -1114,6 +1135,7 @@ tp_init_palmdetect(struct tp_dispatch *tp,
 	/* palm edges are 5% of the width on each side */
 	tp->palm.right_edge = device->abs.absinfo_x->maximum - width * 0.05;
 	tp->palm.left_edge = device->abs.absinfo_x->minimum + width * 0.05;
+	tp->palm.vert_center = device->abs.absinfo_y->minimum + height/2;
 
 	return 0;
 }
diff --git a/src/evdev-mt-touchpad.h b/src/evdev-mt-touchpad.h
index 6ab0981..7b7600c 100644
--- a/src/evdev-mt-touchpad.h
+++ b/src/evdev-mt-touchpad.h
@@ -261,6 +261,7 @@ struct tp_dispatch {
 	struct {
 		int32_t right_edge;		/* in device coordinates */
 		int32_t left_edge;		/* in device coordinates */
+		int32_t vert_center;		/* in device coordinates */
 	} palm;
 
 	struct {
@@ -387,4 +388,7 @@ tp_gesture_post_events(struct tp_dispatch *tp, uint64_t time);
 void
 tp_gesture_stop_twofinger_scroll(struct tp_dispatch *tp, uint64_t time);
 
+bool
+tp_palm_tap_is_palm(struct tp_dispatch *tp, struct tp_touch *t);
+
 #endif
diff --git a/test/touchpad.c b/test/touchpad.c
index b06e00d..cd86f04 100644
--- a/test/touchpad.c
+++ b/test/touchpad.c
@@ -2626,6 +2626,49 @@ START_TEST(touchpad_palm_detect_no_palm_moving_into_edges)
 }
 END_TEST
 
+START_TEST(touchpad_palm_detect_tap)
+{
+	struct litest_device *dev = litest_current_device();
+	struct libinput *li = dev->libinput;
+
+	if (!touchpad_has_palm_detect_size(dev))
+		return;
+
+	libinput_device_config_tap_set_enabled(dev->libinput_device,
+					       LIBINPUT_CONFIG_TAP_ENABLED);
+
+	litest_drain_events(li);
+
+	litest_touch_down(dev, 0, 95, 5);
+	litest_touch_up(dev, 0);
+	litest_assert_empty_queue(li);
+
+	litest_touch_down(dev, 0, 5, 5);
+	litest_touch_up(dev, 0);
+	litest_assert_empty_queue(li);
+
+	litest_touch_down(dev, 0, 5, 90);
+	litest_touch_up(dev, 0);
+	litest_assert_button_event(li,
+				   BTN_LEFT,
+				   LIBINPUT_BUTTON_STATE_PRESSED);
+	litest_assert_button_event(li,
+				   BTN_LEFT,
+				   LIBINPUT_BUTTON_STATE_RELEASED);
+	litest_assert_empty_queue(li);
+
+	litest_touch_down(dev, 0, 95, 90);
+	litest_touch_up(dev, 0);
+	litest_assert_button_event(li,
+				   BTN_LEFT,
+				   LIBINPUT_BUTTON_STATE_PRESSED);
+	litest_assert_button_event(li,
+				   BTN_LEFT,
+				   LIBINPUT_BUTTON_STATE_RELEASED);
+	litest_assert_empty_queue(li);
+}
+END_TEST
+
 START_TEST(touchpad_left_handed)
 {
 	struct litest_device *dev = litest_current_device();
@@ -3681,6 +3724,7 @@ int main(int argc, char **argv) {
 	litest_add("touchpad:palm", touchpad_palm_detect_palm_becomes_pointer, LITEST_TOUCHPAD, LITEST_ANY);
 	litest_add("touchpad:palm", touchpad_palm_detect_palm_stays_palm, LITEST_TOUCHPAD, LITEST_ANY);
 	litest_add("touchpad:palm", touchpad_palm_detect_no_palm_moving_into_edges, LITEST_TOUCHPAD, LITEST_ANY);
+	litest_add("touchpad:palm", touchpad_palm_detect_tap, LITEST_TOUCHPAD, LITEST_ANY);
 
 	litest_add("touchpad:left-handed", touchpad_left_handed, LITEST_TOUCHPAD|LITEST_BUTTON, LITEST_CLICKPAD);
 	litest_add("touchpad:left-handed", touchpad_left_handed_clickpad, LITEST_CLICKPAD, LITEST_APPLE_CLICKPAD);
-- 
2.3.4



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