Scrolling in a vertical direction with a touchpad is stuttery and doesn't maintain scroll inertia unless the movement is perfectly vertical. The bug is not present when using Dolphin 20.08.3; on my Arch install the issue appeared on version 20.12.0, but a build of version 20.11.80 from git contains the bug as well.
Steps to reproduce:
1. Install any Dolphin version >= 20.11.80 on a laptop
2. Open a directory with a long list of files
3. Scroll using the touchpad/trackpoint
Expected result: smooth scrolling that maintains inertia
Observed result: scrolling stops as soon as scrolling movement is not perfectly vertical
I believe the bug might be similar in nature to a Konsole bug reported a few months ago as the expected and observed behaviour are pretty much the same; the bug in question is
Works for me with my trackpad. Are you using libinput or synaptics drivers?
Synaptics, but I'll try to check using libinput as well.
Scrolling using libinput works as expected, although scroll inertia is not preserved (I used the default libinput config so it might be because of that)
Sounds like it's a bug in the Synaptics drivers.
Unfortunately scroll inertia is not built into Libinput. Its developer believes, not unreasonably, that this is a feature the toolkit should handle, as doing it in the driver causes some unfixable bugs in apps. And sadly Qt is not great about supporting it in its scrollviews.
Created attachment 134272 [details]
Compare angleDelta().x() and angleDelta().y() to determine scroll direction
(In reply to Nate Graham from comment #4)
> Sounds like it's a bug in the Synaptics drivers.
Turns out it actually was a Dolphin bug... It's exactly the same as the Konsole one: assuming that a scroll event with and angleDelta().x() != 0 is definitely not a vertical scroll.
Applying this patch fixes the issue
Sent a merge request to the repo, guess I'll change the status of this bug to "fixed"
Merge request: https://invent.kde.org/system/dolphin/-/merge_requests/149
Not fixed until the merge request is merged. :)
Thanks for submitting it!
Git commit 303740c68af83f45be1bdea56a250397a83efa6a by Eduard Manta.
Committed on 23/12/2020 at 16:17.
Pushed by ngraham into branch 'release/20.12'.
Fix vertical scroll with horizontal component not being recognized properly
a scroll that includes an horizontal component != 0 might still be a vertical scroll
M +2 -2 src/kitemviews/kitemlistcontainer.cpp
*** Bug 431410 has been marked as a duplicate of this bug. ***