fw/services/touch: release an active touch when the last subscriber leaves - #1892
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…eaves The last subscriber going away powers the touch sensor down mid-gesture, so a finger that was down at teardown never produces a Liftoff. The Touchdown's backlight hold (light_touch_down -> light_button_pressed) then never unwinds: the button refcount stays pinned, the light never enters its timed state, and with the sensor off no later touch can clear it. Synthesise the Liftoff with the last coordinates when the subscriber count reaches zero, mirroring the teardown the global disable path already performs for the same reason. Co-Authored-By: Claude <noreply@anthropic.com> Signed-off-by: Joseph Mearman <joseph@mearman.co.uk>
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Draft — still validating on hardware.
While playing around with the touch navigation a few weeks ago I kept catching the backlight staying lit well past its timeout, in cases where an app had exited (or otherwise dropped its touch subscription) while my finger was still on the screen.
The last-unsubscribe path powers the sensor down mid-gesture, so the in-progress touch never gets a Liftoff. The Touchdown's backlight hold (light_touch_down -> light_button_pressed) then never unwinds: the button refcount stays pinned, the light never enters its timed state, and with the sensor off no later touch can clear it.
This synthesises the Liftoff with the last coordinates when the subscriber count reaches zero — the same teardown touch_service_set_globally_enabled(false) already performs for exactly this reason, per its own comment.
Covered by test_touch__last_unsubscribe_with_finger_down_emits_liftoff (and a no-finger guard test) in tests/fw/services/test_touch.c; full unit suite green.