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Terminate all stopped/changed touches during SYN_DROPPED in the first frame

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The previous event processing had subtle issues with touches stopping during
SYN_DROPPED. All of the device state was processed in the same frame, but if
any touch changed tracking ID during SYN_DROPPED, an inserted SYN_REPORT
resulted in a weird split of events:
- the first frame had all key/sw/abs updates including those slots that
  changed tracking ID, but not the ones that were fully terminated.
- the second frame had only the slots states for newly started touches **and**
  the slot state for touches terminated during SYN_DROPPED but not restarted.

In other words, where three fingers were on the touchpad and slot 0 was lifted
and put down again and slot 1 was lifted but *not* put down again, our frames
contained:
- frame 1: terminate slot 0, BTN_TOOL_TRIPLETAP 0, BTN_TOOL_DOUBLETAP 1
- frame 2: start slot 0, terminate slot 1

Where there was no touch changing tracking ID, only one frame was generated.
The BTN_TOOL updates were buggy, they may not match the number of fingers down
as seen on a frame-by-frame basis. This triggered libinput bug
https://gitlab.freedesktop.org/libinput/libinput/issues/422

This patch changes the above example to
- frame 1: terminate slot 0, terminate slot 1
- frame 2: start slot 0, BTN_TOOL_TRIPLETAP 0, BTN_TOOL_DOUBLETAP 1

Notably, the first frame no longer contains the BTN_TOOL bits. This patch is
one of two, the BTN_TOOL sync bits are part of a follow-up patch.

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
This commit is contained in:
Peter Hutterer 2020-02-13 21:11:14 +10:00
parent 2056da9517
commit 41de1b0e1a
1 changed files with 31 additions and 13 deletions
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44
libevdev/libevdev.c
View file

@ -740,7 +740,8 @@ terminate_slots(struct libevdev *dev,
bool touches_stopped = false;
for (int slot = 0; slot < dev->num_slots; slot++) {
if (changes[slot].state == TOUCH_CHANGED) {
if (changes[slot].state == TOUCH_CHANGED ||
changes[slot].state == TOUCH_STOPPED) {
queue_push_event(dev, EV_ABS, ABS_MT_SLOT, slot);
queue_push_event(dev, EV_ABS, ABS_MT_TRACKING_ID, -1);
@ -765,7 +766,10 @@ push_mt_sync_events(struct libevdev *dev,
int rc;
for (int slot = 0; slot < dev->num_slots; slot++) {
if (!bit_is_set(changes[slot].axes, ABS_MT_SLOT))
/* stopped touches were already terminated in
* terminate_slots */
if (changes[slot].state == TOUCH_STOPPED ||
!bit_is_set(changes[slot].axes, ABS_MT_SLOT))
continue;
queue_push_event(dev, EV_ABS, ABS_MT_SLOT, slot);
@ -863,11 +867,34 @@ static int
sync_state(struct libevdev *dev)
{
int rc = 0;
bool want_mt_sync = false;
int last_reported_slot = 0;
struct slot_change_state changes[dev->num_slots > 0 ? dev->num_slots : 1];
memset(changes, 0, sizeof(changes));
/* see section "Discarding events before synchronizing" in
* libevdev/libevdev.h */
drain_events(dev);
/* We generate one or two event frames during sync.
* The first one (if it exists) terminates all slots that have
* either terminated during SYN_DROPPED or changed their tracking
* ID.
*
* The second frame syncs everything up to the current state of the
* device - including re-starting those slots that have a changed
* tracking id.
*/
if (dev->num_slots > -1 &&
libevdev_has_event_code(dev, EV_ABS, ABS_MT_SLOT)) {
want_mt_sync = true;
rc = sync_mt_state(dev, changes);
if (rc == 0)
terminate_slots(dev, changes, &last_reported_slot);
else
want_mt_sync = false;
}
if (libevdev_has_event_type(dev, EV_KEY))
rc = sync_key_state(dev);
if (libevdev_has_event_type(dev, EV_LED))
@ -876,17 +903,8 @@ sync_state(struct libevdev *dev)
rc = sync_sw_state(dev);
if (rc == 0 && libevdev_has_event_type(dev, EV_ABS))
rc = sync_abs_state(dev);
if (rc == 0 && dev->num_slots > -1 &&
libevdev_has_event_code(dev, EV_ABS, ABS_MT_SLOT)) {
struct slot_change_state changes[dev->num_slots];
int last_reported_slot = 0;
rc = sync_mt_state(dev, changes);
if (rc == 0) {
terminate_slots(dev, changes, &last_reported_slot);
push_mt_sync_events(dev, changes, last_reported_slot);
}
}
if (rc == 0 && want_mt_sync)
push_mt_sync_events(dev, changes, last_reported_slot);
dev->queue_nsync = queue_num_elements(dev);