Dell Precision 7750 Touchpad MMB Delayed Press Event
Summary
The physical middle mouse button on my Precision 7750 exhibits strange behavior when held down. Libinput successfully detects the button-down and button-up events from the kernel and timestamps them correctly, but refuses to "release" them until after the button is released. Effectively, MMB works to click or select things, but cannot be held down for e.g. CAD software or scrolling purposes.
Consider the following screenshots. The following is of "normal" LMB behavior (interestingly, this is on event11 and not event10, as the MMB is): the event for buton down is received, debouncing code runs, and libinput presents a "pointer button down" event. After release, the debouncing code again runs, and indicates release.
The MMB does not present events until after it is released. (Note the copy-pasted text from when the MMB event reached the terminal application and triggered a paste).
Interestingly, libinput reports the correct start time for the button-down event - it just waits until the button-up event to send this information to the symbol.
Steps to reproduce
- Environment on this machine was KDE Plasma Desktop on Wayland, with no special mouse configuration.
wev
mirrors the behavior, as does various "online mouse button tester" applications. - KDE mouse config:
- Simply launch
sudo libinput debug-events --verbose --device=/dev/input/event10
and observe the unusual behavior. Of course, you may need a Precision 7750 to reproduce the bug, although it may also occur on other Dell devices, or perhaps with all I2C_HID mice.
Required information
-
libinput version: 1.25.0-1, Arch Linux x86_64 Build. Pacman -Qi libinput
-
Hardware: Dell Precision 7750. Touchpad identified as "Dell09c4:00 0488:120a Mouse". Appears to be I2C HID.
-
libinput record
output: record_10.txt- Recording produced by holding button briefly for several cycles, then a few quick presses.
-
libinput debug-events --verbose
output: debug.txt- Produced similarly to the record output.