Speed-based thumb detection causes unreliable scrolling
Submitted by Sebastian Krzyszkowiak
Assigned to Wayland bug list
One of the main issues that drive me away from any libinput-based session towards xf86-driver-synaptics is the way two-finger scrolling is triggered - or, actually, sometimes not triggered - with libinput (with either xf86-driver-libinput, libinput debug tools or various Wayland compositors).
The situation: The pointer is already moving with one finger and the second finger is placed on the touchpad. Expected result: pointer stops to move and content starts to scroll. Result got: pointer continues to move, no scrolling happens.
xf86-driver-synaptics detects all the two-finger scrolls reliably and works as expected. With libinput, I always need to stop moving and only then can start scrolling, which is extremely annoying.
dos@yoga:~$ pacman -Ss libinput extra/libinput 1.9.4-1 [installed]
Laptop: Lenovo Yoga 900-13ISK
Input device name: "Synaptics TM3066-002"
Input device ID: bus 0x18 vendor 0x6cb product 0x77c6 version 0x100
Size in mm: 87x57
The attached recording shows the example misinterpreted touchpad action. libinput-debug-events.txt shows the libinput's misinterpretation. However, when the recording is replayed with evemu-play, it's actually interpreted correctly (as seen in libinput-debug-events-replayed.txt).